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1. PAGE 56 NORSUD WSTES FE FE TE EH EH EH aE FE HE a FE FE HE FE FE HE TE FE HE TE FE FE HE FE EE TE FE HE TE FE FE EE HE TE FE HE TE FE HE TE FE FE EE EE EE HE HEH EE EEE E E E E E E EE E H Field 4 Snow thickness m m SNTOCEAN SNTATMOS 10 86400 6 sstocean sstatmos 92 96 EXPORTED lono lato lona lata oces atmo Li 0 0 1 Analysis CHECKIN MASK EXTRAP INTERP CHECKOUT REVERSE 9999 999999e 06 NINENN 2 SURFMESH Z T T SCALAR 1 naismvoi 0 0 NORSUD WSTEST FE FE HEH RARA FE FE FE HE FE FE HE TE FE HE TE FE HE HE EE HE TE FE HE TE FE FE HE FE FE HE TE EE HEH EE EE EH E TE FE HE RE EE EE EE EE HEH Field 5 Zonal wind stress over water pa pa XWATMOS TXWOCEAN 23 86400 7 flxatmos flxocean 95 91 EXPORTED lona lata lono lato atmo ocev Seq_no Delay Extra_step 1 Analysis INVERT CHECKIN MASK EXTRAP INTERP CONSERV CHECKOUT NORSUD WSTEST 9999 999999e 06 NINENN 2 BICUBIC G T T VECTOR GLOBAL FEFE TE FE HE aH aE E aE FE HE TE FE FE HE FE FE HE TE FE HE TE FE FE EE FE HE HE aE FE FE EE E HE EE TE FE HE TE FE FE HE TE E E TE FE HE EH EH EE EE EEE E E EE E E E H Field 6 Meridional wind stress over water pa pa YWATMOS TYWOCEAN 24 86400 7 flxatmos flxocean 95 91 EXPORTED lona lata lono lato atmo ocev Seq_no Delay Extra_step 1 Analysis INVERT CHECKIN MASK EXTRAP INTERP CONSERV CHECKOUT NORS
2. PAGE 33 Table 4 Grid information files for OASIS DKRZ ECHO G Model Documentation File Unit Content Locator grids 71 atmosphere longitudes atmo lon atmosphere latitudes atmo lat ocean scalar grid longitudes oces lon ocean vector grid longitudes ocev lon ocean scalar grid latitudes oces lat ocean vector grid latitudes ocev lat masks 12 atmosphere land sea 1 0 mask atmo msk ocean land sea 1 0 scalar grid mask oces msk ocean land sea 1 0 vector grid mask ocev msk areas 73 atmospheric gridcell surfaces atmos srf ocean scalar grid cell surfaces oces srf ocean vector grid cell surfaces ocev srf 4 5 Generating the HOPE executable The HOPE executable will reside in directory execs after compilation with the script hope_t42er COMP_HOPE_t42er_1 01 The script uses the make utility Make only compiles those subroutines that have been changed since the last compilation or that depend on code that has been changed since the last compilation It is thus important that the specified dependencies are correct and complete This was strived for however is not guaranteed If preprocessor specifications for conditional compilation gpp options are changed the whole code should be recompiled by activating the line that deletes all binaries In addition to the horizontal resolution one can specify the vertical resolution which is blank for the standard version 20 layers The parameter
3. Similar argument apply to the specification of INVERT for the following 10 fields the atmospheric fluxes These field are transferred from the coarser to the finer grid so we simply use the BICUBIC inter PAGE 37 DKRZ ECHO G Model Documentation polation except for the residual heat flux which should always be positive The exchange fields and their locators are listed in Table 6 on page 38 The unit numbers are read from KONTCTL by SBR READ_KONTCTL and must be changed there and in namcouple if at all Table 6 ECHO G exchange fields PAGE 38 File Unit Content Locator Array name Comment sstocean 92 sea surface temperatures SSTOCEAN THg oACC on ocean scalar grid effective sea ice thickness SITOCEAN SITE ACC y sea ice concentration SICOCEAN SICE ACC i snow depth SNTOCEAN SNTgoACC x sstatmos 96 sea surface temperatures SSTATMOS ATEMP on atmos phere grid effective sea ice thickness SITATMOS AICETH i sea ice concentration SICATMOS AICECO snow depth SNTATMOS ASNCOV i flxatmos 95 zonal wind stress on water TXWATMOS AWUST on atmos phere grid meridional wind stress on water TYWATMOS AWVST i zonal wind stress on ice TXIATMOS AIUST w meridional wind stress on ice TYIATMOS AIVST solid fresh water flux FRIATMOS AIFRE liquid fresh water flux FRWATMOS AWFRE d residual heat flux RHIATMOS AIQRE conductive heat flux CHIATMOS AICON net heat flux over water NHWATMOS AWHE
4. namcouple file The OASIS control file namcouple contains all general information about the set up of the coupled model The same namcouple file can be used for all experiments runs and all grid resolutions To adapt the files to the particular run it will be edited in the integration script before it is read by OASIS Changes e g exchange frequency have to be applied to hope_t42er c03 PREPCCM 45003_c03 see Generating scripts for the integration of ECHO G on page 39 in order that they are introduced to all scripts of the experiment ECHO G uses the version namcouple_fluxes of the files in directory oasis oasis2 2_dkrz The other version is used if the ocean model is forced with fluxes in low and mid latitudes but with surface fields in high latitudes HOPE must then be compiled without specification of the gpp parameter DPFLUXES The file is listed in Section The OASIS control file namcouple on page 49 In namcouple the following parameters are set when the integration scripts are generated or before execution of ECHO G change scripts PREPCCM 45003_c03 to modify them e Anzahl_der_sequentiellen_Modelle replaced by nmseq nmseq 2 1 specifies whether the models are to be run sequentially or parallel e exp id replaced by ocexptid e g c03 e Laufzeit replaced by runtime length in sec of the present run e Jahr_Monat_Tag replaced by YYYY MONTH1 01 YY Y Y is the y
5. Hasw H dsw HAdsw I1 A ll a H A a AsH The net longwave radiation is W DS I Hu H iw H iw arte Allo 1 The downward longwave radiation L and the emissivity are the same over the ice free and ice covered parts of the gridcell denotes the Stefan Boltzman constant The turbulent fluxes of latent heat SE mW DS I Ay H la H la I Q ADD a 18119 g 47 4 10D E AiD Pgl ag 9 and sensible heat ZW ASI Hse Hse Hse S I x a S I 1 A DE 0 s 0 0 A1D dgl 0g 75 are calculated with bulk formulas gt is the air velocity 8 the air temperature and qg the specific humidity at the blending height In ECHAM the values of the lowest model level are used as blending height variables These variables are identical over the ice covered and ice free part of a gridcell The latent heat flux is proportional to the difference of the specific humidity at the blending height and at the surface The specific humidity at the surface is calculated by means of the SST 6 for open water and by means of the skin temperature T for sea ice regions These surface temperatures are also used to determine the sensible heat flux which is proportional to the temperature difference between blending W S I W height and surface The exchange coefficients D Dia D and pe are dependent on the rough PAGE 6 DKRZ ECHO G Model Documentation ness length and the bulk Richardson number R
6. and momentum fluxes are calculated separately for the ice covered and the ice free part of each gridcell in order to account for the strong nonlinear dependences of the fluxes on the surface conditions The fluxes over ice and over water are passed separately to the ocean sea ice model The ocean model is only little changed from the version described in Wolff et al 1997 The changes mainly concern the ice growth routines which do not use heat balance equations any more Instead fluxes as obtained from the atmosphere model areused for the computation of the thermodynamic ice growth The component models are coupled by use of the OASIS coupling software developed at CERFACS It is described in Terray et al 1998 PAGE 1 DKRZ ECHO G Model Documentation PAGE 2 DKRZ ECHO G Model Documentation 2 Model description ECHO G is a coupled climate model CCM that consists of two component models an atmosphere gen eral circulation model AGCM and an ocean sea ice general circulation model OGCM The AGCM ECHAM has been developed from the ECMWF weather forecast model It has been exten sively changed at the Meteorologisches Institut der Universit t Hamburg and at the Max Planck Institut f r Meteorologie in order to adjust the model for climate simulations Cycle 3 of the model ECHAM3 is described in the DKRZ technical report no 6 DKRZ 1993 The performance of ECHAMA which is used for ECHO G is presented in Chen and R
7. fills up land points with sea values to deal with different sea land masks in the models 1 1 extrapolation method NINENN only 2 1 number of neighbors used BLASNEW linear combination of fields after interpolation BLASOLD da ie gt before PAGE 51 DKRZ ECHO G Model Documentation e g fldl al fldlta2 fld2 an fldn 1 1 multiplier of current field al 2 1 number of fields to be combined with the current field n 1 tn 1 lines k 1 n 1 1 k name of additional field 2 k multiplier X gt REDGLO go from a reduced gaussian grid to a global one has to be the last analysis 1 1 SEALAND sea values ar xtended to continental areas using the reduced grid sea land mask LANDSEA the opposite is performed NOEXTRAP no extrapolation is performed GLORED go from a global gaussian grid to a reduced one has to be the first analysis NOINTERP no interpolation case useful with identical grids OASIS then does the synchronization task go from the model array ordering to OASIS conventio S gt N and W gt INV Gi Zo H Gl D 1 1 NORSUD or SUDNOR 2 1 ESTWST or WSTEST REVERSE the opposite of the above INTERP int
8. icelevs which sets the number of ice thickness classes for the heat flux calculation must have the value 1 for the ECHO G component model Parameter OCVERS gives the model version appendix and has to be the same as that specified in the input file 45003_c03 for the script PREPCCM 45003_c03 that generates the ECHO G integration scripts e g 1 0i Some FORTRAN preprocessor options can be activated in the compile script DMATR DOASIS and DPFLUXES are required for the component model HOPE version The other preprocessor options for HOPE are listed in Table 5 on page 35 Those that appear in the model code but are not listed in Table 5 PAGE 34 DKRZ ECHO G Model Documentation should be used with care if at all We also warn the user of HOPE G that of course not all gpp combina tions could be tested Table 5 Fortran preprocessor gpp options for conditional compilation of HOPE G PCFL call of subroutine CFL that checks the CFL criterion each time step PDCONADJ diagnosis of convective adjustment PDIFKOE diagnosis of effective horizontal diffusion coefficients PELIMI direct solution of barotropic system with Gauss elimination PFLUXES forcing with fluxes only required for the coupled version PFWFCORR use of annual mean fresh water flux correction fields PHTMERID diagnosis of meridional heat transport advective and diffusive PMATR reading the barotropic system matrix from disk POASIS set up for coupl
9. FE AE FE HE EE EE EE FE FE FE EE EE EE EE EE EEE EE EE EE HE FE HE EE EE EE EE EEE E H E NBMODEL number of models and their names CHAR 6 SNBMODEL 2 ECHAM4 HT42ER SEND FE E AE aE aE AE aE aE aE AE AE AE AE FE AE AE AE HE FE AE HE AE aE HE aE aE AE Ha HE aH a aH aaa aa aaa RUNTIME lt I8 total simulated time for the actual run in seconds the value will be set before the actual integration SRUNTIME Laufzeit SEND FEE AE aE E AE aE aE A aE AE AE AE AE FE AE A AE AE HE FE AE HE AE aE HE HE aE HAE HE HaHa HaHa aaa aaa INIDATE 18 initial date of the run YYYYMMDD Jahr_Monat_Tag EE HH HEE HH EE EEE FE E FE E EH HE EE ARA EE EE EE EEE H Indicates whether a header is encapsulated within the field YES or NOT SMODINFO NOT SEND lt FE E AE aE AE AE AE E FE AE FE AE AE AE FE FE E AE AE AE FE AE FE AE AE AE FE HE E AE AE AE FE FE FE E AE AE E FE AE FE AE AE E FE AE FE AE AE AE FE FE FE AE AE AE FE FE E AE AE AE FE FE AE AE AE AE E FE FE AE AE Analyses n m is mth parameter of line n MASK masking of a field needed in the extrapolation step call before EXTRAP 1 1 mask value EXTRAP extrapolation
10. FE FE HE EE EE FE AE FE E FE HE TE HE TE HE TE EEE HH Field 9 Solid freshwater flux m s m s RIATMOS FRIOCEAN 28 86400 7 flxatmos flxocean 95 91 EXPORTE lona lata lono lato atmo oces Seq_no Delay Extra_step 1 Analysis INVERT CHECKIN MASK EXTRAP INTERP CONSERV CHECKOUT NORSUD WSTEST 9999 999999e 06 NINENN 2 BICUBIC G T T SCALAR DKRZ ECHO G Model Documentation Seq_no Delay EXTRAP INTE GLOBAL EEE EEE AE AE FE E FE AE E AE AE AE FE AE FE AE AE AE FE FE E AE AE AE FE FE FE AE AE AE MAL flxocean 95 91 EXPORTED Extra_step 1 RP CONSERV CHECKOUT T E SCALAR GLOBAL FEE AE AE AE AE AE AE FE AE FE AE AE AE FE AE E AE AE AE FE AE FE AE AE AE FE FE E E AE AE E FE AE E AE AE AE FE AE FE AE AE AE FE FE FE AE AE AE FE FE E AE AE AE FE FE FE AE AE AE E FE H 4 4 4 Field 10 Liquid freshwater flux FRWATMOS FRWOCEAN 29 86400 lona lata lono lato atmo oces Analysis INVERT CHECKIN MASK NORSUD WSTEST 9999 999999e 06 NINI 4 4 4 Field 11 Residual heat flux RHIATMOS RHIOCEAN 12 86400 lona lata lono lato atmo oces Analysis INVERT CHECKIN MASK NORSUD WSTEST 9999 999999e 06 NINI FERE FE FE HE HE EEE EEE HEHE E E E HEE E E E E E HE HF
11. Field 12 Conductive heat flux CHIATMOS CHIOCEAN 16 86400 lona lata lono lato atmo oces Analysis INVERT CHECKIN MASK NORSUD WSTEST 9999 999999e 06 NINI W M 2 W m 2 Seq_no Delay EXTRAP INTE flxocean 95 91 EXPORTED Extra_step 1 RP CHECKOUT T T SCALAR AE E AE aE AE aE aE aE a aE aE aE aE aE aE aE a W M 2 W m 2 Seq_no Delay EXTRAP INTE BICUBIC G FE AE aE E E AE aE aE aE aE aE AE AE ae aE aE aE AE aE Ea Ea aE H flxocean 95 91 EXPORTED Extra_step 1 RP CONSERV CHECKOUT E T SCALAR DKRZ ECHO G Model Documentation GLOBAL ee a AE AE E FE FE AEAEE E Field 13 Total heat flux over water W m 2 W m 2 NHWATMOS NHWOCEAN 5 86400 7 flxatmos flxocean 95 91 EXPORTED lona lata lono lato atmo oces Seq_no Delay Extra_step 1 Analysis INVERT CHECKIN MASK EXTRAP INTERP CONSERV CHECKOUT NORSUD WSTEST 9999 999999e 06 NINENN 2 BICUBIC G T T SCALAR GLOBAL EEE EEE aE AE AE FE aa AE AE AE FE aaa aaa Field 14 Downwelling solar heat flux W m 2 W m 2 SHWATMOS SHWOCEAN 7 86400 7 flxatmos flxocean 95 91 EXPORTED lona lata lono lato atmo oces Seq_no Delay Extra_step 1 Analysis INVERT C
12. W m sensible heat flux S I 2 H W m total surface heat flux over sea ice excluding o AICON AOFLCHI 5 9 the conductive flux mean conductive heat flux through ice gridcell average Hp AOFLDHWgjo heat flux due to SST relaxation H res W m AIQRE AOFLRHIE o mean surface residual heat flux gridcell average aw H W m AWHEA AOFLNHWE o mean heat flux through open water gridcell average h m fo SICTHg O sea ice thickness gridcell average h S m SNCOV SNTEACC mean snow depth gridcell average PAGE 46 DKRZ ECHO G Model Documentation Table 8 Symbols Variable name Symbol Unit Description Locator atmosphere ocean h eff SICED SITE ACC mean effective ice thickness including isolat ing effect of snow K ZALPHA CON conductivity of ice Ks ZALPSN CONSN conductivity of snow L atmospheric long wave radiation mean momentum flux through the snow ice surface W Mj AWUST j 1 AOFLTX YW zo mean momentum flux on the water surface AWVST j 2 gridcell average j 1 zonal j 2 meridional P APRL APRC precipitation pi rain on sea ice p snow fall on sea ice S I vida i q specific humidity at sea ice snow surface q specific humidity at water surface dg specific humidity at the blending height Ri j Richardson number over water S T i Ri Richardson number over snow ice R continental river runoff Py ZRHOICE RHOICE density of sea ice Ps R
13. advanced by 1 ocean time step in subroutine OCESTEP the same subroutine that is used in the stand alone stan dard version In OCESTEP subroutine OSSTACC is called to accumulate the surface conditions At the end of each coupled time step MOD JO NO 0 HOPE normalises the mean surface condition fields and calls subroutine OCE_WRTE to writes them to file sstocean and the time step to the corre sponding pipes 3 2 Flow chart of ECHAM4 In Figure 4 on page 25 the flow chart of the ECHAM4 routines relevant for coupling are shown A detailed description of the model flow is given in DKRZ 1993 The main program of ECHAM is MAIN different to the ECHAMA4 standard version MAIN calls ATMINI and ATMSTP ATMINI which is based on the standard ECHAM routine CONTROL initialises the atmospheric model In READ_KONTCTL which is called by ATMINI the namelist KONTCTL is read KONTCTL con tains the coupling parameters and is also read by HOPE Thereafter the named pipes FIFOs for data exchange with OASIS are initialised in ATM_PIPE_DEF 10 FIFOs are used for writing the atmosphere to ocean flux fields 4 FIFOs are defined for reading the surface conditions and 2 FIFOs are used to ini tialise the communication between ECHAM4 and OASIS Since the initial conditions are created by HOPE if no OASIS restart files are available in a first run there is no subroutine corresponding to OCE_INI_WRTE ATMSTP is based on the standard ECHAM routine DR
14. and water surface respectively qg is the corresponding value at blending height DI and ge depend on the SST which is provided by the ocean model Two freshwater flux fields are passed to the ocean The first is the gridcell mean freshwater flux which E ad 5 W i 5 indi EEE comprises precipitation P and evaporation E over water continental runoff R and liquid precipitation PAGE 8 DKRZ ECHO G Model Documentation S I rain over ice Pr F 1 A P E R RAP The precipitation calculated in the atmosphere does not depend on the surface type The second freshwater flux field the gridcell mean solid freshwater flux over ice includes the sublima S T S I tion of snow orice E and the snow fall Py MSI S I gE Sher 7 S I S I Ar Ps E DS I The solid freshwater flux F is used to update the snow depth Upward solid freshwater fluxes are used for sublimation of snow and if all snow is consumed the remaining flux is used to sublimate sea ice and then to evaporate water The formulation conserves mass but not heat The sum of both freshwater fluxes is used to update the ocean surface elevation which is a prognostic variable In this way the influence of the snow cover is accounted for in the barotropic pressure gradient that is calculated by use of the sea surface elevation only Consequently a change of ice thickness does not influence the sea surface elevation Its effect on the th
15. land Pa 110 m latent heat flux over sea ice W m PAGE 48 DKRZ ECHO G Model Documentation Table 9 Additional codes for ECHAM4 output Variable Description latent heat flux over open sea W m latent heat flux over land W m evaporation over sea ice m s evaporation over open water m s evaporation over land m s roughness length over sea ice m roughness length over open water m roughness length over land m sensible heat flux over sea ice W m sensible heat flux over open water W m sensible heat flux over land W m albedo of sea ice frac albedo of water frac albedo of land frac AHFICE conductive heat flux W m QRES residual heat flux for melting sea ice W m m denotes mean over output interval The OASIS control file namcouple FE HE AE HE E HEE HH FE AE FE HEHE FE E FE EE FE FE E EEE EE EE FE AE TE EE EEE EE EE EE EE EE EE FE FE FE HE FE E FE HE FE H H Input file for OASIS 2 2 This version is for use of ECHAM4 fluxes and relaxation heat flux computation in the ocean The file will be edited in the run script to update it for the actual integration period and grid dimensions EE AE aE AE AE aE AE FE FE E AE AE AE FE AE E AE AE AE FE FE HE AE AAA FE FE FE AE AE AE FE FE E AE AE AE AE FE FE AE AE AE FE FE H The initial file sstocean for the atmosphere will be written i
16. time step of the ocean and the atmosphere respectively The corresponding variable names in the model source code are found in Table 7 on page 39 Figure 2 does not include the I O on named pipes by which the models are synchronized The dashed arrows have to be interpreted in the sense that each process HOPE ECHAM4 and OASIS that wants to read exchange data has to wait until the data have been written to the file The models are coupled synchronously The fields that are passed to the atmosphere i e SST SIT SIC and SNT are averages of a coupled time step as well All exchanged fields are used without time inter polation 2 1 Heat fluxes SE AW The atmosphere ocean mean heat flux H onsists of the component through the air water interface H and through the air sea ice interface H Positive values denote a flux into the ocean For the descrip tion of the individual heat flux components we concentrate on the dependence on the variables delivered by the ocean model i e sea surface temperature 6 sea ice concentration Ay effective sea ice thickness hos and snow depthh A scheme of the dependencies and of the exchange of coupling variables is dis played in Figure 1 on page 13 ZW The gridcell mean net heat flux through the air water interface H comprises the downwelling short uo W ORIS W wave radiative heat flux H gsw the longwave radiative heat flux H and the turbulent fluxes of latent W W and se
17. use of these files is activated by gpp options at compile time of the ocean Table 5 on page 35 or by setting switches in the ocean which control the ocean model flow The last file named namcouple contains the control information for OASIS It contains information about the general set up of the coupled model no of models sequential or parallel integration interpo lation methods etc and is described in detail in Section 4 7 The namcouple file on page 36 Table 1 also lists the variable names of logical units and the subroutines were the units are set Each unit number is used in one component model or in OASIS only Thus the units used in the previous DKRZ pool version of HOPE have been changed Units used by ECHAM4 are not changed except for the redi rection of the standard output Table 1 ECHO G input files PAGE 18 Unit set in SUSE Description Comment name nulgr 71 grids latitudes and longitudes of all section 4 4 SBR inilun component model gridpoints used by OASIS only nulma 72 masks land sea masks of all compo SBR inilun nent model grids nulsu 73 areas cell areas of all component 1 SBR inilun model grids nulcc 76 mweights weights for interpolation section 4 7 SBR inilun with SURFMESH written read by OASIS kunitow 92 sstocean ocean surface conditions written by HOPE SBR READ_KONTCTL on the ocean grid read by OASIS kunitaw 95 flxatmos atmospheric fluxes written by ECHAM4 SBR
18. 0 indicates that it already exists This is coded in file namcouple only which is used for forced integrations of HOPE G where the forc ing data are read and interpolated by OASIS We recommend that a new set up different grid resolu tions is tested first in an ocean or atmosphere stand alone mode A coupled integration can use the same file mweights For the other parameters of the namcouple file see the OASIS manual Terray et al 1998 The first four exchange fields specified in namcouple_fluxes are those generated by HOPE In the first line for each field the first 2 entries are the locators in sstocean and sstatmos see Table 6 on page 38 The third gives the serial number of the field description in array cfldlab which is defined in SBR oasis oasis_version2 2 srclocal blockdata f This is followed by the number of analyses see third line the alias names of the data exchange files and their logical unit numbers The last parameter of this lines specifies that the field is to be passed to the other model In the second line for each field the first 4 parameters gives the grid dimensions of the data generating and receiving model and the first part of the locators in the grid information files Table 4 on page 34 In the third line for each field key words for the analyses to be performed with the fields are specified With the T42 ocean grid including a meridional grid refinement near the e
19. 1 DKRZ ECHO G Model Documentation PAGE 12 DKRZ ECHO G Model Documentation Figure I Fields exchanged between the component models of ECHO G file with flux correction data Fp Hp a m ECHAM4 HSR 27 el ZA 1 A4 H 0 AH 1 ADH161 AH 1 ADH7101 4 5 AH 16 hog AH hep ER ar MER E an Mau N team A AM PAGE 13 DKRZ ECHO G Model Documentation PAGE 14 DKRZ ECHO G Model Documentation 3 System description When ECHO G is started one process is created for each component model ECHAM4 and HOPE and an additional process is created for OASIS The OASIS process and the model processes are in a UNIX parent child relationship All communication between the models is via OASIS there is no direct com munication between the models themselves The synchronization of the field exchange is done by OASIS With the PIPE concept which is used for ECHO G this synchronization is done by I O on named pipes FIFOs For each exchange field that is passed to OASIS or received from OASIS a corresponding FIFO has to be defined in the models When a model or OASIS is ready to pass a field it first writes the data on a file and then writes its time step number to the pipe that corresponds to that field When OASIS or the model is ready to read the field it first tries to read the corresponding pipe Since this reading is on FIFOs it will wait until the time step message has been written
20. 1 logical unit 3 1 identifier for the mapping data set used to complete the head which are used to read both weights and adresses It is also used to locate these arrays in the macro arrays used within OASIS lt jpnfp in parameter h 4 1 used to read initially the weights and adresses arrays lt jpmoa in parameter h IN OUT can be used to follow precisely the field values before and after interpolation Extrema and mean value are calculated for the global earth the sea and the land If the integral flag is 1 the field integrals are calculated as well All the results are printed in the OASIS output file Note that they have no input parameters and no input lines LEE Line 1 Source file name amp u Target bi gt EEE AE AE aE aE HE aE AE HE AE HE Ha HE aE EEE Locator of exchanged field on source grid Locator of exchanged field on target grid Label number for internal oasis output see cfldlab in blkdata f Exchange frequency for the field in seconds Number of analyses to be performed nit numbers for data transfer n Field status EXPORT ED or AUXILARY If EXPORTED the fie If AUXILARY the fie ld is both received and sent after interpolation ld is just received and used within OASIS It is given to the other model Line 2 Number of longitudes latitudes di longitudes Y l
21. 8 Sausen R S Schubert L Diimenil 1994 A model of the river runoff for the use in coupled atmosphere ocean models J Hydrology 155 337 352 Stendel M and E Roeckner 1998 Impacts of Horizontal Resolution on Simulated Climate Statistics in ECHAM 4 Report No 253 Max Planck Institut fiir Meteorologie Hamburg 57 pp Terray L S Valcke and A Piacentini 1998 The OASIS Coupler User Guide Version 2 2 Tech Rep TR CMGC 98 05 CERFACS 77 pp Wolff J O E Maier Reimer and S Legutke 1997 The Hamburg Ocean Primitive Equation Model Technical report No 13 German Climate Computer Centre DKRZ Hamburg 98 pp PAGE 61 DKRZ ECHO G Model Documentation PAGE 62
22. A downwelling solar heat flux SHWATMOS AWSOL fixocean 91 zonal wind stress on water TXWOCEAN AOFLTXWgo on ocean vector grid meridional wind stress on water TYWOCEAN AOFLTYWgjo zonal wind stress on ice TXIOCEAN AOFLTXIp o 3 meridional wind stress on ice TYIOCEAN AOFLTYIp o a DKRZ ECHO G Model Documentation Table 6 ECHO G exchange fields File Unit Content Locator Array name Comment solid fresh water flux FRIOCEAN AOFLFRI go on ocean scalar grid FRWOCEAN AOFLFRWgjo RHIOCEAN AOFLRHIg o dl CHIOCEAN AOFLCHIp o 3 NHWOCEAN AOFLNHWgjo SHWOCEAN AOFLSHW 9 liquid fresh water flux residual heat flux conductive heat flux net heat flux over water downwelling solar heat flux 4 8 Generating scripts for the integration of ECHO G A script is provided with scripts PREPCCM 45003_c03 that creates scripts to run ECHO G Again the working and home directories have to be changed to the directory name where the data and source tar files have been expanded Also the experiment ID e g 45003_c03 and the name of the machine where the model will be run have to be specified e g lake Before the script can be run the program MAKELST_CCM comp has to be compiled The minimum length of an integration is one month the maximum length one year All months of one scipt have to be of the same year The first and last job number and the length in months of the integra tion
23. G_n n_data_cray tar Results of two runs of one month length are found in ECHO G_n n_result_cray tar These tar files as well as a post script version ECHO G_tech_rep_n n ps of this manual are available on the DKRZ file server in direc tory pool modelle echo g Figure 5 on page 41 and Figure 6 on page 43 show the directory trees which are created by the source and data tar files respectively when they are expanded Directories at the end of dashed lines will not be created by expanding one of the tar files but during the execution of one of the scripts contained in the tar files Section 4 1 and Section 4 2 gives a summary of the contents of the directories Note that the source and data directory trees contain identical paths Thus the source and data files must be expanded in different directories e g pf and mf Before any of the scripts is started do not forget to change the path names above the directories that are set up by the tar files the home and working directories to the directories where the tar files have been expanded 4 1 Contents of directories source code sbrs F source code of HOPE that is used for all grid resolutions sbrs_t42er F source code of HOPE which depends on the model grid scripts scripts to generate ECHO G integration scripts oasis all source code and programs related to OASIS oasis sbrs_oasis F source code needed to set up HOPE as a component model of ECHO G oasis oasis_version2 2 s
24. HECKIN MASK EXTRAP INTERP CONSERV CHECKOUT NORSUD WSTEST 9999999999806 NINENN 2 BICUBIC G T T SCALAR GLOBAL EEE EEE HE aE aE HE aE aE HH HE A Ha aE HaHa aaa aa SEND PAGE 59 DKRZ ECHO G Model Documentation PAGE 60 DKRZ ECHO G Model Documentation 6 References Chen C T and E Roeckner 1996 Validation of the earth radiation budget as simulated by the Max Planck Institute for Meteorology general circulation model ECHAM4 using satellite observations of the Earth Radiation Budget Experiment J Geophys Res 101 4269 4287 DKRZ 1993 The ECHAM3 Atmospheric General Circulation Model Technical report No 6 German Climate Computing Centre DKRZ Hamburg 188 pp Groetzner A R Sausen and M Claussen 1996 The impact of sub grid scale sea ice inhomogeneities on the performance of the atmospheric gen eral circulation model ECHAM3 Climate Dynamics 12 477 496 Legutke S 1999 Climatology of the HOPE G global ocean sea ice general circulation model Technical report German Climate Computer Centre DKRZ Hamburg in preparation Roeckner E K Arpe L Bengtsson M Christoph M Claussen L Diimenil M Esch M Giorgetta U Schlese and U Schulzweida 1996 The atmospheric general circulation model ECHAMA4 model description and simulation of present day climate Max Planck Institut f r Meteorologie Hamburg Report No 21
25. HOSNO density of snow C sea level lo STBO Stefan Bolzmann constant Tireez K C CTFREEZ TFREZ freezing point of sea water Tee TMELT TMELT freshwater melting temperature i final snow ice skin temperature at step n S T eee A To preliminary snow ice skin temperature at step n PAGE 47 DKRZ ECHO G Model Documentation Table 8 Symbols Variable name Symbol Unit Description Locator atmosphere ocean aW Ta air water surface stress aS I Ta Pa air ice surface stress Pa ice water surface stress defines climatolgical ice region air temperature at blending height D H w Ur TSW SST g QACC mean upper layer ocean temperature lt DI dy l air velocity at the blending height D m s SICU VEJo sea ice velocity Dd m s Ugio upper layer ocean velocity Az ZDICE depth of upper snow ice layer whose tempera ture is affected by the surface heat balance AZOW roughness length over water AZOI roughness length over snow ice MID Table 9 Additional codes for ECHAM4 output Code Acc Variable Description 101 m TEFFW surface temperature of open water K 102 TSI surface temperature of sea ice K 103 TSW surface temperature of open water K 104 m USTRI zonal windstress over sea ice Pa 106 m USTRW zonal windstress over open sea Pa 107 m meridional windstress over open sea Pa 109 m VSTRL meridional windstress over
26. IVE The routine STEPON called by ATMSTP advances the model by one atmosphere model time step At the beginning of each coupled time step MOD JA NA 1 ATM_READ is called in STEPON This routine reads the pipes corresponding to the oceanic surface condition fields and then from file sstatmos the oceanic surface conditions SST sea ice thickness and coverage and snow thickness over sea ice provided by HOPE via OASIS PAGE 16 DKRZ ECHO G Model Documentation In order to perform an atmospheric time step several routines are called in STEPON for details see DKRZ 1993 Among other routines COLLECT is called via SCAN1 GPC and PHYSC COLLECT accumulates the atmosphere ocean flux components which are transferred to HOPE via OASIS At the end of a coupled time step MOD JA NA 0 these flux components are averaged in ATM_AVRG and written to file flxatmos in ATM_WRTE Both routines are called in STEPON The atmospheric time step is written to the corresponding FIFOs in ATM_WRTE as well This is the signal for OASIS that the flux fields are available now and can be read and interpolated to the ocean grid In order to have separate output files for all component models and OASIS the model standard output of ECHAMA4 is redirected to file atmout 3 3 Input files The coupled model needs some additional input files which are listed in Table 1 on page 18 Table 1 con tains only those files which are relevant for the co
27. MO only 6 1 unit to write flux correction to Mi for 5 and 6 see CORRECT CONSERV insure local or global flux conservation CORRE 1 1 GLOBAL or LOCAL LOCAL has no effect yet CT do field correction with external data flux correction 1 1 multiplier of current field 2 1 number of fields to be combined with the current field n 1 lines k 1 n 1 1 k name of additional field 2 k multiplier y D 3 k file name of additional field 4 k logical unit SUBGRID restore subgrid variability in a field when the resolution are very different The idea here is to add a term proportional to Delta T Toce Tatm and to conserve the fluxes The added has the spatial oceanic variability as it contains Toce for each oceanic mesh This can be necessary for Pacific simulation where the atmosphere never really feels the cold tongue due to markedly different resolutions call with MOZAIC 1 1 symbolic names for the 3 fields appearing in the first order Taylor expansion 2 1 31 case a used to interpolate the non solar heat flux with the following formula gt gt Qo Qa dQa dTa To Ta linear approximation This can be helpful if one wants to differentiate the non solar heat flux between two types of surface ocean and ice present in the OGCM grid squares underneath one AGCM grid square case b used to interpolate the solar hea
28. O G internal files Unit set in File Description Comment kunitar 96 sstatmos ocean surface conditions on the written by OASIS SBR READ_KONTCTL atmospheric grid read by ECHAM4 kunitor 9 1 flxocean atmospheric fluxes on the ocean written by OASIS SBR READ_KONTCTL grids read by HOPE PAGE 20 DKRZ ECHO G Model Documentation Figure 2 Scheme of the time integration of ECHO G HOPE G Start OCE_MAIN ECHAM4 Start MAIN Initialise HOPE Initialise ECHAM4 JO 0 JA 0 surface cond on ocean grid Write initial sur face conditions JO JO 1 surface 1 cond on Read mean fluxes J Advance one ocean time step flxocean uxes 8 4 1 Write mean surface conditions lt NO NC lt NA NC PAGE 21 DKRZ ECHO G Model Documentation PAGE 22 DKRZ ECHO G Model Documentation Figure 3 Flow chart of component model HOPE G HOPE G Start OCE_MAIN OCEINI Read namelist of coupled model READ_KONTCTL Define FIFOs Write read initial message OCE_PIPE_DEF lt I gt yes Write initial conditions and time step OCE INI WRTE E JO JO 1 1 Initialise surface condition arrays Advance one ocean time step OCESTEP 0 Average surface conditions OCE_AVRG Write sur cond write time step to FIFOs OCE_WRTE FIFOs coupled time step atmo
29. PAGE 28 DKRZ ECHO G Model Documentation 3 7 Subroutines needed to set up the uncoupled ECHAM4 Two steps are needed to get the coupled version from the standard ECHAM4 e improved description of the atmosphere ocean interaction which can also be used with the uncou pled model e technical changes which are needed for the exchange of information with OASIS The modifications of the uncoupled ECHAM4 are described in the following and the coupling routines are presented in Section 3 8 3 7 1 Subgrid scale atmosphere ocean fluxes The physical changes concern the atmosphere ocean fluxes of partly sea ice covered gridcells In con trast to the standard ECHAMA the fluxes of a gridcell over open water and sea ice are calculated sepa rately This method has been developed by Groetzner et al 1996 for the ECHAM3 To implement this method the routines VDIFF calculation of turbulent fluxes of the boundary layer SKINTEM calcu lation of the sea ice skin temperature RADINT and RADHEAT calculation of shortwave and long wave radiation have to be updated An additional diagnostic heat flux component which describes the surface melting of sea ice by atmosphere fluxes QRES is calculated in SKINTEM Due to the separate computation of the fluxes for land open water and sea ice additional field codes for the ECHAM4 out put are introduced These additional output variables contain the individual subgrid scale fluxes A list of these variab
30. READ_KONTCTL on the atmosphere grid read by OASIS nlunkon 51 KONTCTL ECHO G control variables NAMELIST read by SBR OCEINI HOPE and ECHAM4 DKRZ ECHO G Model Documentation Table 1 ECHO G input files Unit set in Alias we Description Comment name nlunpat 57 PATEMP monthly climatological SST read by HOPE SBR OCEINI lunfwf FWFCORR a m fresh water flux correc SBR PBOPEN tion lunfwf HTFCORR a m heat flux correction SBR PBOPEN nulin 4 namcouple OASIS control variables read by OASIS Program COUPLE 3 4 Output files The standard output of HOPE ECHAMA4 and OASIS is directed to the files oceout atmout and cplout respectively The logical units are set in subroutine inilun for OASIS in MAKESD for ECHAMA4 and in OCEINI for HOPE Table 2 ECHO G output files Unit set in pee Description Comment name nout 6 atmout ECHAM4 std output SBR MAKESD nulou 79 cplout OASIS std output program COUPLE nlunout 7 oceout HOPE std output SBR OCEINI nulcc 76 mweights weights for interpolation with SURFMESH see section 3 3 and SBR inilun section 4 7 PAGE 19 DKRZ ECHO G Model Documentation 3 5 Internal files Table 3 lists additional files which are used internally by ECHO G and contain the ocean surface condi tions interpolated to the atmospheric grids sstatmos and the atmospheric fluxes interpolated to the ocean grids flxocean Table 3 ECH
31. Technical Report No 18 The Hamburg Atmosphere Ocean Coupled Circulation Model ECHO G StephanieLegutke and Reinhard Voss Deutsches Klimarechenzentrum Bundesstra e 55 D 20146 Hamburg Edited by Modellberatungsgruppe DKRZ Hamburg March 1999 ISSN 0940 9327 DKRZ ECHO G Model Documentation PAGE 4 ABSTRACT ECHO G is a global coupled atmosphere ocean climate model whose component models are the ECHAM atmosphere general circulation model and a global version of the Hamburg Ocean Primitive Equation model HOPE G which includes a dynamic thermodynamic sea ice model with snow cover ECHO G can be used in numerical studies of natural variability of the world climate and of climate changes on time scales ranging from the component models time steps to centuries In high latitudes the interaction between ocean and atmosphere can be strongly affected by the sea ice cover In particular the heat flux through ice and that through leads and polynyas can differ by an order of magnitude on horizontal scales much smaller than that of a gridcell in global climate models ECHO G accounts for these effects by a separate calculation of fluxes over ice and over water when a sub grid scale partial ice cover is present Since the component models are used in their stand alone versions with only some subroutine calls added and since the coupling interface OASIS is a flexible tool that allows to change the number of component models of inte
32. UD WSTEST 9999 999999e 06 NINENN 2 BICUBIC G T E VECTOR GLOBAL DKRZ ECHO G Model Documentation PAGE 57 EHH EE EH FE AE FE EEE FE FE FE E FE EEE EE EE EE EEE EE EE FE HE FE HE 446 EE EEE EERE EE REE E E H Field 7 Zonal wind stress over ice Pa Pa XIATMOS TXIOCEAN 3 86400 7 flxatmos flxocean 95 91 EXPORTE lona lata lono lato atmo ocev Seq_no Delay Extra_step 1 Analysis INVERT CHECKIN MASK EXTRAP INTERP CONSERV CHECKOUT NORSUD WSTEST 9999 999999e 06 NINENN 2 BICUBIC G T T VECTOR GLOBAL FE E E HE E AE FE HE FE HE FE AE FE AE FE AE FE AE FE E FE E FE FE FE E FE FE FE FE FE FE FE AE TE AE FE AE FE AE FE AE FE FE FE E FE FE FE FE HE E HE FE HE FE HE FE AE FE E FE E TE HE TE FE E E E E E E E E Field 8 Meridional wind stress over ice pa pa YIATMOS TYIOCEAN 4 86400 7 flxatmos flxocean 95 91 EXPORTE lona lata lono lato atmo ocev Seq_no Delay Extra_step 1 Analysis INVERT CHECKIN MASK EXTRAP INTERP CONSERV CHECKOUT NORSUD WSTEST 9999 999999e 06 NINENN 2 BICUBIC G T T VECTOR GLOBAL HEE EH EE 4 AE FE AE FE EE HE EE E FE FE FE FE EE EE EE EE EE EE EE FE AE FE FE
33. ace albedo of melting sea ice c Pade J kg K ZCPICE CLB specific heat of snow ice DI turbulent exchange coefficient of latent heat over water S I Dia turbulent exchange coefficient of latent heat over snow sea ice De turbulent exchange coefficient of sensible heat over water S I 5 De turbulent exchange coefficient of sensible heat over sea ice D turbulent exchange coefficient of evaporation over water S I 5 3 D turbulent exchange coefficient of evaporation over sea ice D turbulent exchange coefficient of momentum over water S I Dn turbulent exchange coefficient of momentum over sea ice At s DTIME time step of the atmosphere model At Bin DT time step ofthe ocean model E m s EVAP evaporation DKRZ ECHO G Model Documentation Table 8 Symbols Variable name Symbol Unit Description Locator atmosphere ocean S I f 3 E m s EVAPI sublimation of snow ice E i m s evaporation over water emissivity SII F m s AOFLFRIp o mean solid freshwater flux gridcell average aW F AOFLFRWgjo mean liquid freshwater flux gridcell average Fp FWFCORRg 9 fresh water flux due to SSS relaxation flux at time step n flux through air snow ice interface flux through air water interface atmosphere ocean heat flux AWSOL AOFLSHW o ala SS incoming shortwave radiative heat flux downward component of shortwave radiation longwave radiative heat flux Ai W m latent heat flux H e
34. ained in Table 8 on page 45 2 4 Flux corrections Corrections to the heat and freshwater fluxes can be done by either applying heat and freshwater fluxes which correspond to a relaxation of the SST and SSS to specified temperature or salinity fields e g cli matologies or by reading and applying time constant fields of heat and freshwater fluxes that have been generated before Relaxation related fluxes can be calculated only in the ocean model Their calculation is activated by spe cific FORTRAN preprocessor switches gpp options see Table 5 on page 35 Note that the salinity relaxation fluxes are set to 0 at gridcells where the specified climatological surface temperature is below the freezing point plus a specified temperature offset T Thus there is no SSS relaxation within a cli matological ice region which is defined through the specified temperature field and the offset The SST relaxation related fluxes are applied in all cells They do not depend on the ice concentration The time constant fields of heat and freshwater flux corrections that are supplied with the model see Table 1 on page 18 have been calculated in a 100 year coupled run of ECHO G where monthly clima tological AMIP SSTs were used for the calculation the SST relaxation fluxes AMIP SSTs that were colder than freezing point were set to freezing point before the calculation of the relaxation fluxes PAGE 10 DKRZ ECHO G Model Documentation 2 5 Interpo
35. alone integration of ECHAM4 with a T42 resolution and climatological AMIP SST prescribed at the lower boundary As was already mentioned for the atmosphere it should be relatively easy to set up a CCM with any of the resolutions for the ocean that are in use at DKRZ At a specified frequency the atmosphere component model passes heat fresh water and momentum to the ocean and receives surface conditions This frequency is the same for all exchange fields in the ver sion described here and defines the lengths of a coupled time step The fields that are exchanged have been averaged over the last coupled time step The atmosphere ocean fluxes are calculated in the atmosphere model The atmosphere needs to know the mean sea surface temperature SST 0 the mean sea ice concentration SIC Ay the mean effective sea ice thickness SIT heff and the mean snow depth SNT hs of the last coupled time step Fluxes are calculated separately over water and sea ice The method used here to account for a sub gridscale partial ice cover is described in Groetzner et al 1996 It is based on the blending height concept which PAGE 3 DKRZ ECHO G Model Documentation assumes that the atmospheric variables are horizontally homogeneous over each gridcell in a certain height the blending height The blending height is defined as the height where the atmospheric flow changes from equilibrium with the local surface conditions to independenc
36. atitudes Acronyms used to loc Sequential index of the data generating model on source grid n n n target 2 n n n ate the data in the grid description files e g if SEQMODE 2 and model 1 2 are atmosphere ocean and the run is to be initi alized with ocean SST only then this parameter is 1 for the ocean meaning that the ocean lable first output is avai 0 gt 0 do not do delay of field exchange SEOMODE gt 1 set N 0 odel if it is to re N F by N coupled time st If m F lag to compute ane lag used to delay the field exchange eps in the case of parallel models SEQMODE 1 N 0 for the input flux fields of the first ceive the first flux fields via OASIS xtra timestep 1 yes 0 no PAGE 54 DKRZ ECHO G Model Documentation NORSUD WSTES PAGE 55 This flag can be used if one wants to perform an additional exchange for the current field 10 Flag to compute the field integral 1 yes 0 no This flag tells OASIS to calculate the integral
37. cean 4 9 Integrating ECHO G When all component models and OASIS have been compiled successfully and scripts for the integration have been generated the experiment can be started by submitting the first integration script When this script has been run successfully it will automatically submit the next script to integrate the next MANZ months and so on until all scripts provided for the experiment are executed Model output will be written to the directories as described in Section 4 2 Contents of directories data on page 32 With each ECHO G integration script a second script is generated which saves the model output on the file server This script is submitted by the corresponding integration script when the latter has finished If it is executed successfully it removes itself the corresponding integration script and the data it saved including the standard output files ECHAM4 output is saved every months HOPE output once a year The restart files are saved every MANZ months Small files as ZEITR and HTMERID are saved only at the end of a decade Thus at the end of each decade the only trace on the compute server that is left by an experiment of which all aspect are run successfully is the standard output files of the data saving scripts These should be checked regularly in order to be sure that no problems occurred during the data saving process If the data are not saved successfully the data saving script resubmits it
38. d alone version The thermodynamic ice growth routine GROWTH now exclusively uses atmo spheric fluxes while the stand alone version uses near surface atmospheric fields in ice regions The coupled model is set up by specifying the gpp options DPFLUXES and DPOASIS in the HOPE com pile script If DPFLUXES is not specified but DPOASIS a stand alone version of HOPE is set up that uses the same forcing data as does the version alreay in the DKRZ model pool however the reading of the data and the interpolation to the ocean grid is done by OASIS The subroutines that are needed to set up the ocean component model ready to be used with OASIS can be found in directory oasis sbrs_oasis F the other subroutines needed for the compilation of HOPE reside in directory sbrs F and sbrs_t42er F The latter directory contains subroutines that are specific for the particular resolution of the ocean model 3 6 1 Main program OCE_MAIN In the HOPE pool version the main program that controls the ocean model integration is OCEMAST Since this program also reads the forcing data and calls an interface that interpolates the data between the atmosphere and ocean grids it has been replaced The main program of the component HOPE version is called OCE_MAIN It controls the ocean integration and the reading and writing of exchange fields as depicted in Figure 3 on page 23 3 6 2 Subroutine READ_KONTCTL Subroutine READ_KONTCTL sets defaults for the ECHO G control var
39. e of horizontal position in the cell ECHAM is formulated on a hybrid vertical coordinate system where the lower levels use terrain following 6 coordinates while the upper levels become surfaces of constant pressure We take the low est level of the atmosphere model to be the blending height which lies ca 30 m above the bottom The fluxes through the ice covered and the ice free part of each gridcell are calculated from the atmospheric variables at the blending height and the oceanic surface fields SST SIT SNT and SIC The net atmospheric flux for an atmosphere gridcell is the horizontal average of the fluxes through the ice free and ice covered surface of the gridcell weighted by the fractional areas of the respective sur faces The mean total flux of a coupled time step that has to be applied to the ocean and sea ice is thus A FL 1 A FLY NTATMOS n 1 NTATMOS f TR i 1 where NTATMOS is the number of atmospheric time steps per coupled time step and F E sF Er stand for any of the atmospheric fluxes at time step n over the snow ice and water surface respectively Over bars denote mean values of a coupled time step The fluxes through the ice free and ice covered surface of a gridcell are passed to the ocean as mean fluxes relative to the total gridcell surface denoted by curved overbars SI FL yA FL NTATMOS n 1 NTATMOS ZW w FL 1 A FL NTATMOS n 1 NTATMOS Exceptions are the w
40. e on the SST 6 which is passed over from the ocean model The water velocity and the sea ice velocity gt are not passed over from the ocean in the present version of the coupled model Both velocities are set to zero in the atmospheric model Momentum fluxes are also passed in two fields the erdoi mean wind stress acting on the water surface M j and the stress acting on the snow ice surface mM The wind stress on ice is passed to the ocean without averaging over the gridcell area It will be used in the sea ice momentum equation see Wolff et al 1997 The momentum flux into the Ocean system derived from the air ice stress is A Mj A From the ice velocity the water ice stress T is calculated with a quadratic stress law see Wolff et al 1997 In order to account for sea ice concentration changes in a gridcell during a coupled time step the air water momentum flux is corrected by the mismatch of the momentum flux in the atmosphere and the ice ocean The momentum flux applied to the ocean is thus W S I M 1 A M A A Mj A Ty A summary of the fields that are exchanged by ECHO G and the variables that directly depend on these fields is displayed in Figure 1 on page 13 Besides the dependencies listed in Figure 1 there are additional indirect dependencies and dependencies which occur only if conservation of heat or mass could not be guaranteed otherwise The symbols used in the formulas are expl
41. ear MONTHI the first runof the coupled experiment e Seq_no replaced by iseq sequential no of the atmosphere mode 1 for parallel execution e Extra_step replaced by exstep 1 if an extra OASIS step is to be done at the end of the run to save data e Delay replaced by delay n if the reading of the exchange fields by the model is to be delayed by n time steps nmseq iseq exstep and delay depend on whether the component models are run parallel or sequential and on whether surface conditions as well as fluxes are available at the start of the run We use 2 2 0 0 respectively for a first run no flxatmos available RERUN is then FALSE i e the component mod els run sequentially and only the ocean exchange data surface conditions are provided by OASIS at the beginning of the first coupled time step In continuation runs RERUN is then TRUE sstocean and flxatmos are available the exchange fields of both component models are passed to the other model by OASIS at the beginning of the first coupled time step and the models are integrated parallel PAGE 36 DKRZ ECHO G Model Documentation e the grid dimensions of ocean and atmosphere lato lata lono and lona e naismvoi replaced by anaismax the maximum number of ocean gridcells underlying an atmosphere grid cell e niwtm replaced by anaismwr 1 indicates that the weight file mweights is generated by OASIS and written to disk
42. erpolation from one grid to another 1 1 interpolation method NNEIBOR BILINEAR BICUBIC SURFMESH GAUSSIAN 2 1 source grid type L uniform R reduced gaussian G gaussian Z irregular U unstructured not yet implemented 3 1 periodicity of source grid true or false T or F 4 1 periodicity of target grid 5 1 field type SCALAR or VECTOR 6 1 rank for interpolation data file identifier for anaism g relevant data in file mweights gweights GAUSSIAN or SURFMESH only maximum no of arrays must be specified in parameter h 7 1 maximum number of overlapped neighbors di 8 1 flag for generation of weights Compute read 1 0 Di 9 1 Variance of gaussian interpolation GAUSSIAN only FILLING complete a regional dataset with global data 1 file name for the global data set 1 logical unit 1 filling technique XXXYYYZZ XXX SMO or RAW smoothing or no smoothing YYY 2 SST O STE SST or sea ice extent ZZ MO or SE or AN interanual monthly climatlogical monthly annual WN RE PAGE 52 DKRZ ECHO G Model Documentation 4 1 1 or 0 YYY SST only coastal correction no coastal correction 5 1 symbolic name for the array containing the difference between the initial SST and the SST modified by a smooth filling XXX S
43. he ocean initial surface conditions to sst ocean and time step information to the corresponding pipes It is recommended to compile this routine without any optimisation or multitasking 3 6 5 Subroutine OCE_READ OCE_READ reads the pipes related to the atmospheric flux fields and then the corresponding exchange fields that are passed by OASIS from the atmosphere to file flxocean It is recommended to compile this routine without any optimisation or multitasking 3 6 6 Subroutine OSSTINI At the beginning of each coupled time step subroutine OSSTINI resets the arrays where the surface con ditions are accumulated 3 6 7 Subroutine OCE_AVRG At the end of each coupled time step the accumulated surface conditions are normalised in subroutine OCE_AVRG and the effective ice thickness is calculated from the gridcell mean ice thickness and snow depth see Heat fluxes on page 5 The mean sea ice concentration is interpolated from the scalar to the vector grid for later use in the sea ice ocean surface stress calculation in subroutine OCWIND 3 6 8 Subroutine OCE_WRTE OCE_WRTE writes the mean surface condition fields to file sstocean and the ocean time step is written to the corresponding pipes 3 6 9 Subroutine PIPE_DEF Auxiliary subroutine to define a FIFO 3 6 10 Subroutine locread This OASIS subroutine performs a localized read on the file containing the exchange fields for details see Terray et al 1998
44. i This stability parameter is computed separately for open water and ice covered regions and depends on the surface temperature roughness length z and the blending height values of temperature and wind Ri Ri 6 05 p 201 S I S I tr pS I S I Ri T 8 Dp Zo Ri A more detailed description of the turbulent surface fluxes is given in Roeckner et al 1996 The gridcell mean conductive heat flux through the snow ice layer H Il Sa Cc A SP herp Il is used for bottom ablation or accretion of sea ice It is assumed that within a time step the temperature profile within the ice layer adjusts to the surface conditions and is thus linear The effective ice thickness herp Kz h stKs h Kk ni Ay is introduced to account for the different thermal conductivities of snow and ice K andky are the heat conductivities of sea ice and snow respectively hy and hg are the gridcell mean thicknesses of sea ice and snow respectively The gridcell mean residual heat flux causes surface melt of snow or ice S T For its computation a preliminary new skin temperature T of the snow ice layer is calculated first by use of a heat flux balance at the surface S T S T Tn K asl S I 5 1 x 7 EB M DO De Azz a hos pyc A is the specific heat of sea ice or snow and At the time step of the atmosphere The surface heat fluxes are formulated with the skin temperature PE of the la
45. iables and reads the NAMELIST KONTCTL This namelist which overwrites the control variables is also read in ECHAM4 with the same routine READ_KONTCTL checks the synchronization of the restart files of the compo nent models 3 6 3 Subroutine OCE_PIPE_DEF OCE_PIPE_DEF initialises the communication between OASIS and HOPE It defines 2 named pipes FIFOs for the initial information exchange with OASIS one pipe for writing to OASIS named RDhopt42 and one pipe for reading named WThopt42 HOPE writes the total number of time steps the number of time steps per coupled time step the length of its time step and its process ID to RDhopt42 OASIS uses this information from all component models to define its own time step and check the con sistency between the time stepping and exchange frequency of the different models The corresponding information of OASIS is read by HOPE from WThopt42 OCE_PIPE_DEF also defines the pipes for synchronization of field exchange one reading pipe for each of the 10 flux fields received from the atmo PAGE 27 DKRZ ECHO G Model Documentation sphere and one writing pipe for each of the 4 surface condition fields sent to the atmosphere It is recommended to compile this routine without any optimisation or multitasking 3 6 4 Subroutine OCE_INI WRTE Subroutine OCE_INI_WRTE is called at the beginning of an experiment if no OASIS restart files sst ocean flxatmos are available LRERUN false It writes t
46. ickness of the upper ocean layer is however taken into account in the calculation of the upper ocean salinity and the vertical mixing parameteriza tions Since the sea surface elevation is a prognostic variable there is no need to specify salt fluxes through the surface Instead all freshwater fluxes can be transformed directly into changes of the sea surface eleva tion The salinity is then adjusted to the new upper layer thickness with the total salt content being con served Accordingly if sea ice is created or melted this implies an upward or downward freshwater flux respectively for the computation of the upper layer salinity and a corresponding salt flux of the same direction depending on the sea ice salinity and the ice volume change Since the sea ice salinity is smaller than the upper ocean salinity melting of sea ice is associated with a freshening of the upper ocean 2 3 Momentum fluxes aw The momentum fluxes for the atmosphere water interface M i and the atmosphere sea ice interface rn M are calculated with bulk formulas in the atmosphere model ZW S I M M M E Wra id W 7 nS I S I ADD 1011 voy v 7 Ay vel vg Y5 PAGE 9 DKRZ ECHO G Model Documentation The index j 2 stands for the zonal and meridional vector component respectively w I DA vi The exchange coefficients D and D depend on the stability Richardson number see Heat fluxes 1 sala on page 5 and especially D
47. ind stress on the ice covered area and the downwelling solar radiation To close the freshwater budget a routing scheme for the freshwater fluxes over land Sausen et al 1994 is implemented to provide a continental runoff into the ocean The net freshwater flux over glacier regions namely Greenland and Antarctica is accumulated each coupled time step and is distributed to the ocean cells neighboring the coast of the respective region This is done instantaneously without accounting for a time lag between the net snow fall and the freshwater input near the coast In the stan dard version of ECHAMA the net precipitation in the glacier regions mainly snow fall is lost for the hydrological cycle since melting of glaciers or glacier calving is not simulated The time integration is outlined in the diagram of Figure 2 on page 21 Solid arrows indicate the model flow while dashed arrows indicate data I O There is no direct communication between the component models All data exchange is via OASIS The first run in an experiment with ECHO G is initialized with PAGE 4 DKRZ ECHO G Model Documentation ocean surface variables only if LRERUN false initial surface fields SST SIT SIC and SNT are writ ten to the file sstocean which contains the exchange fields generated by the ocean In Figure 2 NC is the number of coupled time steps of the run JO and NO and JA and NA are the model time step and the number of model time steps per coupled
48. ing with OASIS required for the coupled version PTSADUP upwind advection for tracers temp sal PSBGRD sub grid scale redistribution of net atmospheric heat flux PSHFLUX diagnosis of heat budget under ice PSYNOUT additional output of time stepping messages PTRIAN calculation of the barotropic system matrix PVTURKOE diagnosis of effective vertical diffusion viscosity coefficients 4 6 Generating the ECHAM4 executable The atmosphere component model executable of ECHO G ECHAM4 is generated by successively run ning COMP_ECHAM4 130_1 0a then COMP_ECHAMA4_t30_1 0b and COMP_ECHAM4 130_1 0i which are found in directory echam4_t30 These scripts use the nupdate facility If the model is compiled on the J90 lake the preprocessor option V64 must be activated The update file for COMP_ECHAM4_t30_1 0a is found in directory anselm By this update ECHAM4 PAGE 35 DKRZ ECHO G Model Documentation is enabled to separately calculate fluxes through different surface types of inhomogenous gridcell sur faces partial ice cover The update files for COMP_ECHAM4_t30_1 0b and COMP_ECHAMA4_t30_1 01 are found in directory updcoup_t30_t42er By the first update the standard output of ECHAM4 is redirected to file atmout This is useful in order to have separate output files for the component models The second update file introduces additional code that is needed to set up ECHAM as a component model of ECHO G 4 7 The
49. it 18 which defines the glacier cells of the atmosphere grid where the glacier runoff is accumulated and the ocean cells of the atmosphere grid where fresh water is distrib uted PAGE 29 DKRZ ECHO G Model Documentation 3 8 Subroutines needed to set up the component model ECHAM4 3 8 1 Subroutine READ_KONTCTL see Subroutine READ_KONTCTL on page 27 3 8 2 Subroutine ATM_PIPE_DEF ATM _PIPE_ DEF initialises the communication between OASIS and ECHAMA It defines two named pipes FIFOs for the initial information exchange one pipe for writing to OASIS named RDpsech4 and one pipe for reading named WTpsech4 ECHAM4 writes the total number of time steps the number of time steps per coupled time step the length of its time step and its process ID to RDpsech4 OASIS uses this information from all component models to define its own time step and check the consistency between the time stepping of the different models The corresponding information of OASIS is read from WTpsech4 ATM_PIPE_DEF also defines the pipes for synchronization of field exchange one reading pipe for each of the 4 oceanic surface condition fields and one writing pipe for each of the 10 atmosphere ocean flux fields sent to the ocean It is recommended to compile this routine without any optimisation or multitasking 3 8 3 Subroutine ATM_READ ATM_READ reads the pipes related to the oceanic surface condition fields and then the corresponding exchange fields that are
50. lation between atmosphere and ocean grids The interpolation from the atmospheric grid to the ocean grids and vice versa is done with the OASIS software developed at CERFACS Terray et al 1998 With this software the interpolation method can be chosen by keyword specification in the OASIS control file namcouple Table 1 on page 18 All interpolation schemes use only the sea cell values to interpolate between the grids Note that the conti nental runoff is projected on sea cells as well Total fluxes through the sea surfaces of the component models are conserved With a T30 resolution for the atmosphere and a T42er resolution for the ocean the horizontal grid of the ocean is much finer than that of the atmosphere in particular in the tropics There are as much as 40 ocean gridcells underlying one atmosphere cell In order to avoid aliasing effect which could occur with point interpolation methods ECHO G uses an area averaging scheme for the interpolation of the SST SIT SIC and SNT The value transferred to an atmosphere gridpoint is the spatial average of the oceanic val ues of those gridcells that are overlapped by the atmosphere cell weighted by the relative areas that are taken up by the ocean gridcells The interpolation from the atmosphere to the ocean is from the coarser to the finer grids The wind stress over water and that over ice or snow are interpolated with a bicubic interpolation scheme which guarantees smooth
51. les is given in Table 9 on page 48 3 7 2 Continental runoff To ensure a closed hydrological cycle for the coupled system a scheme for the continental river runoff and a scheme for the calculation of freshwater input to the ocean from glaciers Greenland and Antarc tica are added to the standard version of ECHAM4 Both schemes are only diagnostic tools for the uncoupled ECHAM4 whereas the treatment of the subgrid scale atmosphere ocean fluxes always affects the model climate in a stand alone as well as in a coupled integration The applied runoff scheme has been developed by Sausen et al 1994 The update for ECHAMA con tains a set of additional routines to save restart fields HISTRUN to initialise INIROP INIRUNO and to run the scheme RUNO COLRUN DISRUN Beside the unit for the restart fields 81 three addi tional units are needed for the boundary conditions of the runoff scheme 82 83 84 In the standard ECHAM4 runoff from continental ice sheets is not considered Due to a positive net freshwater flux onto both glacier regions of the model Greenland and Antarctica these regions normally constitute a sink for the hydrological cycle To close the freshwater budget for the coupled system the freshwater flux is accumulated separately over both glacier regions and distributed along the respective coast lines The corresponding input due to latent heat of fusion is added to the heat flux In subroutine INIGLAC a mask is read from un
52. lly SSEQMOD Anzahl_der_sequenti n_Mode ll SEND 4 4 4 FE AE HE TE FE HE TE FE HE TE FE FE HE TE FE EE EE EE HE EE HE EEE EHH IEEE y y SMACHINE CRAY SEND DEE aE aE AE EE HE aE aE HEE Ea CHANNEL CHAR 4 PIPE if named pi for sync CLIM if sockets for sync SCHANNEL PIPE SEND E E AE aE E AE aE aE AE aE aE AE AE aE aE aE A aE aE aE aE aE AE aE SNFIELDS 14 SEND DEE HE aE AE AE AE HE aE aE HEE AE aE JOBNAME acronym for the give MACHINE CRAY if the coupl ed model is n n EAE AE AE AE AE AE FE FE FE EH pes binary hro and data are used for hro and dat PRETI RETTE n simulation the value will be set before th PAGE 50 FEFE TE EE HE F FE 4444 E E EEH H run on a cray CHAR 4 YON a workstation FE E AE aE AE AE AE AE FE FE E AE AE AE FE FE E AE AE AE FE HE AE AEAEE FE FE H files are used respectively message passing both a use of the Cerfacs library based on PVM3 3 AE E AE aE E AE aE AE AE aE AE AE AE AE aE EE AE AE aE aE HE aE a FE FE H NFIELDS total number of fields being exchanged E AE AE aE aT AE aE AE FE aE aE AE AE HE aE AE AE aE HE aE aE HE aE aE FE H CHAR 3 actual integration DKRZ ECHO G Model Documentation SJOBNAME exp id SEND EHH HEE FE AE FE HE
53. m4_t30 45003_c03 output ECHAM4 output files echam4_t30 45003_c03 restart ECHAMA4 and OASIS restart files execs executables bin binaries of the component models 4 3 Generating the OASIS executable We use release 2 2 of the OASIS software of CERFACS Terray et al 1998 A compile script is provided PAGE 32 DKRZ ECHO G Model Documentation with oasis oasis2 2_dkrz COMP_OASIS job It can be specified whether all libraries only the local mod ifications or the interpolation libraries shall be created or a combination of these All libraries must be recreated if any of the include COMMON blocks are changed All directories that will be used but do not exist at execution time will be created The OASIS executable will reside in directory execs after com pilation We keep the OASIS source directory tree organization as it is provided by CERFACS below directory oasis_version2 2 Local versions of the subroutines in directory src reside in directory srclocal at the same directory level Local versions of the include files of directory include reside in directory include local etc 4 4 Generating the grid information files The OASIS grid information files see Table 1 on page 18 are provided in directory hope_t42er oasis cpl data of the data tar file A script that generates these files can be found in oasis oasis2 2_dkrz Create_gridinf job and the program is compiled with Comp_gridinf job of the
54. n OCEINI for LRERUN F When the models are to be run parallel in the first run SEQMODE 1 the exchange of the fields generated by the models with sequential number larger than 1 have to be delayed An extra oasis time step PAGE 49 DKRZ ECHO G Model Documentation is then required for thes EEE aE A AE AE HE HE aE HEE Ea EE Input delimiters have to No blank lines allowed Length of input lines lt If number of exchanged field identifier is changed e fields HEHEHE HE HH HH occupy posit 80 fields gt modify related OCE ATM_P If locators for latitudes IPE_DEF subr FE E AE aE aT AE aE aE FE aE aE aE AE aE aE EE aE HE aE aE HE aE EE FE H ion 1 to 9 outine accordingly langitudes masks areas are changed gt modify related GRID_WRTE subroutine accordingly FEE AE aE E AE aE aE FE aE aE AE aE AE HE aE A AE AE HE aE aE HE aE AE aE aE aT TE EE HE AE E AE aE E AE aE aE aE aE aE aE aE aE aE AE aE HE Ea EE FE H s run simultaneously SEOMODE 1 if all mode n if n models run sequentia
55. n of heat within the ocean Thus heat conservation is no critical point for its transfer and it can be multiplied by the actual ice concentration in the ocean model This field is transferred without the factor 1 A The net heat flux H updates the upper ocean temperature Depending on the value of the new ocean temperature relative to T the freezing point of sea water and the direction of the total heat flux minus the surface residual heat flux net plus conductive heat flux the total heat is used to melt ice increase or decrease or increase the ice volume or a combination of this If the net heat flux has the potential of creating new ice that is if the flux is upward and the new upper level temperature is at the freezing point of sea water the ice compactness will be updated by that part of the gridcell that will be covered by new ice ice production due to net heat flux only if this assumes a specified minimum thickness see Wolff et al 1997 2 2 Freshwater fluxes The only freshwater flux component which directly depends on the variables provided by the ocean model is the evaporation aW asS I E E Q ADDY 6 1d 9 0 101 AD Palar Evaporation strongly depends on the local stratification due to the dependence of the bulk transfer coef Ww S I ficients D and D S I W e onthe Richardson number Ri see Heat fluxes on page 5 q and q are the specific humidities at the ice snow
56. nsible heat 7 and H W H 1 ApR W W W W 1 A Hasw Hw Hia He DS I The corresponding heat flux through the air sea ice interface H consists of the downwelling short E 5 1 a S I wave radiative heat flux A the longwave radiative heat flux 77 the turbulent fluxes of latent and S5 I S 1 y a sensible heat H and H e the conductive heat flux through the sea ice H and a residual heat flux H es describing the surface melting of sea ice DS I a mM aa S I S I S I S I Ax Hasw Hiw Hig bp EHet Hes PAGE 5 DKRZ ECHO G Model Documentation AS I dal 5 S I The heat flux between air and sea ice H determines the sea ice skin temperature T which repre sents a boundary condition for the sea ice covered regions in ECHAM The downward component of the solar radiance H depends on the incoming shortwave radiation H ow 2 hs For snow covered sea ice the albedo ranges from 0 75 to 0 85 and for snow free ice from 0 66 to 0 75 1 x and on the albedo of water a and of sea ice as The latter is a function of the snow thickness depending on the surface temperature For temperatures above T the freezing point of fresh water melt the respective minimum albedo is chosen and for temperatures below T 10K the respective melt maximum albedo is applied Between these values the albedo is a linear function of the surface temper ature AW DS I
57. oeckner 1996 and Roeckner et al 1996 Modifications of the ECHAM4 component model in ECHO G relative to the standard version at DKRZ concern the treatment of the net atmospheric freshwater flux on the continental glaciers Greenland and Antarctica the continental river runoff and the method of flux calculation which accounts for a partial ice cover For the CCM described herein we have used a version of ECHAM4 with 19 levels and a horizontal res olution of T30 corresponding to an approximate horizontal gridpoint distance of 3 75 It should how ever be relatively easy to set up a CCM with any of the other resolutions used at DKRZ T21 T42 T63 T106 The performance of the T30 L19 version of ECHAMA is described in Stendel and Roeckner 1998 The HOPE G model used in ECHO G is formulated on a Gaussian T42 Arakawa E grid ca 2 8 with grid refinement at low latitudes acronym t42er Approaching the equator the meridional gridpoint dis tance becomes increasingly smaller with the smallest separation between two lines of the same parity being 0 5 The vertical resolution is by 20 horizontal layers This model is based on the code that is avail able from the DKRZ model pool and is described in Wolff et al 1997 The simulated climate of the ocean model that was obtained in a spin up integration with cyclically repeated daily forcing of a 15 year period is described in Legutke et al 1999 The forcing data were produced in a stand
58. of the field this implies you have asked for analysis CHECKIN and CHECKOUT which calculates other quantities useful for debuging FE FE TE FE FE EH EH aE FE HE TE FE FE HE FE FE HE TE FE EE FE FE HE FE EE HE HE TE HE EE EE EEE HE FE FE FE HE TE EE EE HE HE HE EE EE E E E E E EE EE Field 1 Ocean sea surface temperature K K SSTOCEAN SSTATMOS 1 86400 6 sstocean sstatmos 92 96 EXPORTED lono lato lona lata oces atmo 1 0 0 1 Analysis CHECKIN MASK EXTRAP INTERP CHECKOUT REVERSE 9999 999999e 06 NINENN 2 SURFMESH Z T T SCALAR 1 naismvoi 0 0 4 4444 E HE FE FE FE FE ATRAE E E E EEE H Field 2 Sea ice thickness m m SITOCEAN SITATMOS 9 86400 6 sstocean sstatmos 92 96 EXPORTED lono lato lona lata oces atmo 1 0 0 1 Analysis CHECKIN MASK EXTRAP INTERP CHECKOUT REVERSE 9999 999999e 06 NINENN 2 SURFMESH Z T T SCALAR 1 naismvoi 0 0 NORSUD WSTES 4 4444 E HE HE FE FE EERE EERE HEE EERE EERE EERE EGE HEGRE E E E E E HEE HEHE HEHE Field 3 Sea ice concentration SICOCEAN SICATMOS 8 86400 6 sstocean sstatmos 92 96 EXPORTED lono lato lona lata oces atmo 1 0 0 1 Analysis CHECKIN MASK EXTRAP INTERP CHECKOUT REVERSE 9999 999999e 06 NINENN 2 SURFMESH Z T T SCALAR 1 naismvoi 0 0 DKRZ ECHO G Model Documentation
59. on of the values for the atmosphere cell This file can be generated by OASIS Its generation is quite CPU time consuming It can be saved however after the first run and used in the following integrations The file sstocean contains the initial ocean surface conditions for an experiment It can be generated in subroutine OCEINI or provided by the user This file has to be in the OASIS format as well i e for each exchange field it contains one record with the locator followed by one record with the field data The locator used by ECHO G for the exchange fields are summarized in Table 6 on page 38 PAGE 17 DKRZ ECHO G Model Documentation In a continuation run ECHO G reads initial data also from file flxatmos This file as well as the actual sstocean has been saved by ECHO G at the end of the preceding run of the experiment The NAMELIST KONTCTL contains the control variables for the time looping of ECHO G It is read by the ocean as well as by the atmosphere in subroutine READ _KONTCTL This subroutine checks whether the component models restart files are synchronised The file PATEMP contains monthly climatological SST It is used in HOPE for the computation of the flux correction data by relaxation of ocean SST to climatological SST Annual mean fresh water and heat flux correction data can be read from file FWFCORR and HTFCORR The use of SST SSS relaxation or flux corrections or none of them and thus the
60. ource code of OASIS for more details on OASIS see Terray et al 1998 oasis oasis_version2 2 local local DKRZ versions of OASIS subroutines oasis oasis2 2_dkrz scripts to generate the OASIS executable and the OASIS grid information files hope_t42er script to compile the HOPE G ocean model PAGE 31 DKRZ ECHO G Model Documentation hope_t42er sbrs_hope_1 0i f source code of HOPE after FORTRAN preprocessing echam4_t30 scripts to compile the ECHAM4 atmosphere component model of ECHO G echam4_t30 anselm update file to account for partial ice cover in ECHAM4 echam4_t30 updcoup_t30_t42er update files to set up ECHAM4 as a component model of ECHO G echam4_t30 45003_c03 scripts to run ECHO G 4 2 Contents of directories data forcing flux correction data forcing echam4_clim land sea mask of ECHAM4 T30 oasis cpl lib OASIS binaries and libraries after compilation hope_t42er input files for HOPE bathymetry barotropic system matrix hope_t42er c03 HOPE output of experiment 45003_c03 hope_t42er c03 abend HOPE output of experiment 45003_c03 if an abnormal end occurred hope_t42er c03 output HOPE output files hope_t42er c03 restart HOPE restart files hope_t42er oasis cpl data grid information data for OASIS echam4_130 initial input files for ECHAM4 echam4_130 45003_c03 standard output files of all component models and OASIS echam4_130 45003_c03 abend ECHAMA output of experiment 45003_c03 if an abnormal end occurred echa
61. passed from the ocean to file sstatmos by OASIS It is recommended to compile this routine without any optimisation or multitasking 3 8 4 Subroutine COLLECT This routine accumulates the atmosphere ocean flux fields used for coupling 3 8 5 Subroutine ATM_AVRG Subroutine ATM_AVRG normalises the accumulated fields distributes the accumulated net fresh water flux of the glaciers to the coastal sea cells and calculates the latent heat of fusion for the glacier runoff 3 8 6 Subroutine ATM_WRTE ATM_WRTE opens the file flxatmos to which the atmosphere ocean fluxes are written The normalised fields are written to the file and the atmospheric time step is written to the corresponding pipes 3 8 7 Subroutine PIPE_DEF and subroutine locread see Subroutines needed to set up the component model HOPE G on page 27 PAGE 30 DKRZ ECHO G Model Documentation 4 User s manual This section describes how the standard version of ECHO G is set up and run on a CRAY machine of the DKRZ n n is the release number 1 01 is taken to be the actual version no of ECHAM and HOPE 45 is the user ID used to identify the user of ECHO G 003_c03 gives a serial number for the actual experiment of which the last three letters only are used by HOPE and OASIS The OASIS release no is 2 2 All source code necessary to set up this version of ECHO G is contained in the tar file ECHO G_n n_source_cray tar and all data input files are contained in ECHO
62. period of the scripts to be generated by PREPCCM 45003_c03 are specified with JOB1 and JOB2 and MANZ PREPCCM 45003_c03 will then generate JOB2 JOB1 1 scripts each for the integration of MANZ months where the first script starts at month JOB1 1 MANZ 1 and the last script ends at month JOB2 MANZ The ECHO G control variables in NAMELIST KONTCTL are provided with the integration scripts They are listed in Table 7 Table 7 ECHO G control variables Variable name Description NTAOSTOP number of coupled time steps NTOCEAN number of ocean time steps per coupled time steps NTATMOS number of atmosphere time steps per coupled time steps NATOFF age in model time steps of atmosphere initial file NOCOFF age in model time steps of ocean initial file NTSAVE frequency for saving of ocean restart files PAGE 39 DKRZ ECHO G Model Documentation Table 7 ECHO G control variables Variable name Description NWINTER frequency for saving of atmosphere restart files NRESUMC atmosphere time step at which the run is resumed LRERUN true for continuation runs Table 7 on page 39 NSTOPC atmosphere time step at which the run is stopped KUNITAR unit where the atmosphere reads exchange data file sstatmos KUNITAW unit where the atmosphere writes exchange data file flxatmos KUNITOR unit where the ocean reads exchange data file flxocean KUNITOW unit where the ocean writes exchange data file ssto
63. quator res_oce t42er and the T30 resolution for the atmosphere res_atm t30 the ocean grid is always finer than the atmosphere grid To avoid aliasing effects we use the SURFMESH surface averaging method to interpolate the fields from the ocean to the atmosphere grid This method uses the file mweights which contains the weights of the ocean grid values for interpolation This file can be generated in a first run by OASIS with anaismwr 1 in the integration script Since its generation is quite expensive it should be saved and read from disk in subsequent runs set anaismwr 0 For the standard DKRZ ECHO G version the file is provided in hope_t42er oasis cpl data If a new mweights file is generated take care that the maximum number of overlapping cells anaismax is the same when the file is generated and used Accumulated values of the input and output fields of the global sea and land surfaces are calculated when CHECKIN and CHECKOUT are specified All interpolation methods use only values from sea cells Values on land cells are extrapolated from sea cells before the interpolation using 2 neighboring points NINENN 2 The OASIS ordering of arrays is from south to north and west to east The ocean fields are written to file sstocean according to this convention Before the fields are written to sstatmos their meridional direc tion will be reversed by specification of REVERSE so that they will be written in the ECHAM4 order
64. rpolation methods and data exchange frequencies by keyword specification it should be relatively easy to include other models or change the coupling strategy This report describes the physical and technical aspects of a specific set up that is in use at DKRZ 1 Summary 2 Model description 4 User s manual 5 Appendix A 6 References DKRZ ECHO G Model Documentation Table of Contents 2 1 Heat fluxes 2 2 Freshwater fluxes 2 3 Momentum fluxes 2 4 Flux corrections 2 5 Interpolation between atmosphere and ocean grids System description 2 00 0 ee ee o 3 1 Flow chart of HOPE G 3 2 Flow chart of ECHAM4 3 3 Input files 3 4 Output files 3 5 Internal files 3 6 Subroutines needed to set up the component model HOPE G 3 7 Subroutines needed to set up the uncoupled ECHAMA 3 8 Subroutines needed to set up the component model ECHAM4 4 1 Contents of directories source code 4 2 Contents of directories data 4 3 Generating the OASIS executable 4 4 Generating the grid information files 4 5 Generating the HOPE executable 4 6 Generating the ECHAM4 executable 4 7 The namcouple file 4 8 Generating scripts for the integration of ECHO G 4 9 Integrating ECHO G DKRZ ECHO G Model Documentation DKRZ ECHO G Model Documentation List of Figures Figure 1 Fields exchanged between the component models of ECHO G Figure 2 Scheme of the time integration of ECHO G Fig
65. same directory For the standard DKRZ version of ECHO G the resolution of the ocean and the atmosphere horizontal grids are specified as res_oce _t42er T42 plus equator refinement for HOPE G and res_atm _t30 T30 triangular truncation for ECHAM4 in both scripts The other values for res_oce and res_atm given in the scripts relate to other resolutions of the component models used at DKRZ Note that the HOPE arrays have additional columns used for the specification of zonal cyclic boundary conditions These columns are not included in the grid information files The script may try to access directories of the DKRZ file server This is the case if any of the files are not found on the working directory specified in the scripts These files are also needed for the HOPE G stand alone pool version and are described in the HOPE manual Wolff et al 1997 The grid information files will be saved with the ocean model and atmosphere model resolutions appended to their names Their content together with the locator see Input files on page 17 are listed in Table 4 on page 34 The appendices of the locators are defined in oasis oasis_version2 2 srclocal blk data f The first part of the locator names is set in oasis sbrs_oasis F GRIDINEF The home and working directories have to be changed in the script to the directories where the tar files have been expanded All directories that will be used but do not exist at execution time will be created
66. self and retries to save the data two hours later PAGE 40 DKRZ ECHO G Model Documentation Figure 5 Directory tree that is set up with file ECHO G_n n_source_cray tar Zelle le Een EEA sbrs F sbrs_t42er F oasis hope_t42er echam4_t30 scripts sbrs_hope_1 0i f oasis2 2_dkrz oasis_version2 2 sbrs_oasis F include includelocal lib src srclocal anaisg anaism fscint pipe pipelocal Bee AO AN i echam4 AGRV pl echam4 AGRCSLO pl anselm 45003_c03 updcoup_t30_t42er PAGE 41 DKRZ ECHO G Model Documentation PAGE 42 DKRZ ECHO G Model Documentation Figure 6 Directory tree that is set up with file ECHO G_n n_data_cray tar forcing execs oasis I I I echam4_clim cpl I I lib Sese abend hope_t42er c03 oasis I I I i cpl I I I I I I data I I ro t output restart I abend PAGE 43 echam4_t30 45003_c03 initial I I I I I I I I I I I I I er 1 output restart DKRZ ECHO G Model Documentation PAGE 44 DKRZ ECHO G Model Documentation 5 Appendix A Table 8 Symbols PAGE 45 Variable name Symbol Unit Description Locator atmosphere ocean i an time mean of one coupled time step S I for sea ice covered part of a grid cell uf for water covered part of a grid cell A frac SEAICE SICE oACC sea ice concentration a frac ALSOW ALBW surface albedo of water or frac ALBSN M surface albedo of melting snow ALBI M surf
67. spatial derivatives The heat and freshwater fluxes are also interpolated with a bicubic scheme An exception is the residual heat flux which is positive by definition and is interpolated linearly Near the equator the meridional scale of the ocean grid and the scale of natural SST patterns are much finer than that of the atmosphere grid At least the heat flux between ocean and atmosphere should respond to these patterns This however is not possible if the fluxes are calculated in the atmosphere using the mean upper layer ocean temperature averaged over the atmosphere gridcells In order to partly correct this we redistribute the net atmospheric heat flux that enters the ocean cell group that underlies a single atmosphere cell in a manner that the total heat flux through the cell group surface is conserved and that the heat through each cell of a group is proportional to the difference between the local ocean SST and an effective atmosphere near surface temperature This effective atmosphere near surface temperature is calculated by assuming that the net heat flux is proportional to the effective atmosphere near surface temperature with a proportionality constant of 40 WH Kin This subgrid correction is done in the tropics only where the meridional scale differences of the ocean and atmosphere grids are largest It can be de activated by specification of symbolic names for conditional compiling gpp options PAGE 1
68. spheric MR OASIS fluxes surface conditions FIFOs HOPE ao r F b 4 time step Be A nl lt NO NC PAGE 23 DKRZ ECHO G Model Documentation PAGE 24 DKRZ ECHO G Model Documentation Figure 4 Flow chart of component model ECHAM4 ECHAM4 Start MAIN Initialisaton Read namelist of coupled model READ_KONTCTL Define FIFOs Write read initial message ATM_PIPE_DEF FIFOs ECHAM4 Time stepping ATMSTP STEPON JA JA 1 1 Read FIFOs and surface conditions ATM READ ni y Advance one atmosphere time step time step sstatmos oceanic sur face condi Be ee ee a tions div routines MOD JA NA 0 Average fluxes ATM_AVRG y Write fluxes write time step to FIFOs ATM_WRTE 4f flatmos atmosphere fluxes PAGE 25 DKRZ ECHO G Model Documentation PAGE 26 DKRZ ECHO G Model Documentation 3 6 Subroutines needed to set up the component model HOPE G The component model HOPE differs from the stand alone model by only a small number of additional subroutine calls which concern the data exchange with OASIS and some minor other changes of the code The latter are related to the use of the atmospheric forcing fields which is different from that of the stan
69. st time step except for the conductive heat flux through the ice which is formulated implicitly H Sa denotes the total surface flux excluding the conductive heat flux For the formulation of the time derivative it is assumed that the surface heat flux is absorbed in the upper Az 70 cm of the snow ice layer B S T f 3 The skin temperature T is not allowed to rise above 7 the freezing point of fresh water If this happens it is reset to 7 and the surface heat equation is solved once more with the new and final 8 1 I skin temperature e Min T T gen PAGE 7 DKRZ ECHO G Model Documentation S I n S I T BUN K I Lain SS 80 T H T 01 T Ez nes Ne a heff 1 H res Of all the heat fluxes only the residual heat flux H es that is always positive does not directly enter the ocean It is first used to melt snow then to melt ice Only when all ice and snow is melted the remaining heat is added to the total heat flux and enters the ocean AW The atmosphere passes four heat flux fields to the ocean the net heat flux over open water 7 the con ductive heat flux through the snow ice cover H the residual heat flux at the snow ice surface H res and the downwelling solar heat flux H Lom The latter is only used for penetration of solar radiation into deeper ocean layers It is applied to the ice free part of the gridcell and just implies a vertical redistribu tio
70. t flux with the following formula gt gt QSo QSa 1 Ao 1 Aa where Ax is the albedo for he fifth one tells OASIS hich one of the cases a or b is appropriate NONSOLAR or SOLAR the appropriate grid square Input parameters the first four input parameters are identical to those previously described for the MOZAIC analysis THE SAME WARNINGS APPLY REGARDING PARAMETERS jpnfs and jpsoa T WwW If it is NONSOLAR there are thr more parameters giving the symbolic names of the fields which are going to be used in the above formula First If it is SOLAR there are two more parameters giving the symbolic Ta second To and third dQa dTa names of the fields which are going to be used in the above formula First MOZAIC in contrast to SURFMESH where the weights might be calculated by Aa and second Ao oasis or specified by the user they must be specified by the user for MOZAIC bug in 2 0 attention Weights on land points can be non zero This can be useful for exemple for the runoff PAGE 53 which CHECK CHECK 4 4 SSTRINGS TRINGS STRINGS 1 2 3 4 5 amp 6 7 DKRZ ECHO G Model Documentation is given on land points 1 1 logical file name 2
71. the CCM control data from NAMELIST KONTCTL In subroutine OCE_PIPE_DEF the FIFOs are defined There are 4 writing FIFOs associated with the sur face conditions 10 FIFOS for the reading of the atmospheric fluxes see Figure 1 on page 13 and two additional pipes through which the communication between HOPE and OASIS is initialised PAGE 15 DKRZ ECHO G Model Documentation At the beginning of a coupled experiment LRERUN F i e if no OASIS restart files are available ini tial ocean surface conditions are written to file sstocean and timestep information to the corresponding pipes by calling OCE_INI_WRTE The component model with model number 1 ECHAM4 specified in the namcouple file then starts the first coupled time step and the other model HOPE waits until the first fluxes calculated in the first coupled time step are available HOPE then starts its first coupled time step parallel to the second coupled time step of ECHAM4 which reuses the surface conditions provided by the HOPE initialisation At the beginning of a coupled time step MOD JO NO 1 OCE_READ is called to read the pipes cor responding to the atmospheric flux fields and then to read the fluxes from file flxocean NO and NC are the number of ocean time steps per coupled time step and the number of coupled time steps respec tively JO is the HOPE time step counter Then the exchange fields generated by HOPE are initialised in subroutine OSSTINI HOPE is
72. to the pipe Only then the fields will be read from the file This synchronization can be done in a mode where the integration of the component models over one coupled time step is sequential or parallel For more details on the OASIS concept see Terray et al 1998 ECHO G is initialised with the ocean surface conditions only file sstocean in the first run of each exper iment Continuation runs are initialised with both the ocean surface conditions and the atmospheric fluxes file flxatmos of the last coupled time step A flow chart of the time stepping of ECHO G is dis played in Figure 2 on page 21 see Model description on page 3 3 1 Flow chart of HOPE G A more detailed flow chart of the HOPE G component model is shown in Figure 3 on page 23 It includes only those aspects of the model flow that are relevant for the coupled version For the HOPE model flow charts see Wolff et al 1997 The main program of HOPE in its component model version is OCE_MAIN OCE_MAIN first calls OCEINI to initialise HOPE reading of topography restart files or initial stratifi cation specification of model parameters etc as in the standard stand alone version Only some parts of the code that are associated with the reading of forcing data are not included in OCEINI The model standard output is redirected to an extra file named oceout in order to have separate standard output files for all component models and OASIS Then HOPE reads
73. upled model Each component model also requires input files which are needed in stand alone runs as well These are described in the respective manuals The first four files of Table 1 are needed by OASIS for the interpolation These are named grids masks areas and mweights They all have the OASIS file format as do the next two that is they must be unformatted with sequential access mode For each array they contain one record with an 8 byte character locator and one record with the array data The locator of the OASIS files are summarized in Table 4 on page 34 Section 4 4 Generating the grid information files on page 33 describes how these files are generated For the specific set up of the coupled model provided by the DKRZ these files are provided as well and need not be generated as long as the model is run on a machine with binary com patibility to the CRAY C90 The grids file contains the latitudes and longitudes masks the land sea mask 0 for land 1 for sea and areas the surface areas of the grid cells of each grid of all component models For the interpolation from the finer ocean grid to the coarser atmosphere grid we use an area averag ing method activated by the keyword SURFMESH in the OASIS control file namcouple This method uses the file mweights which for each atmosphere cell contains the weights of the values of ocean cells used for the calculati
74. ure 3 Flow chart of component model HOPE G Figure 4 Flow chart of component model ECHAM4 Figure 5 Directory tree that is set up with file ECHO G_n n_source_cray tar Figure 6 Directory tree that is set up with file ECHO G_n n_data_cray tar 13 21 23 25 41 43 DKRZ ECHO G Model Documentation Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Table 8 Table 9 DKRZ ECHO G Model Documentation List of Tables ECHO G input files ECHO G output files ECHO G internal files Grid information files for OASIS Fortran preprocessor gpp options for conditional compilation of HOPE G ECHO G exchange fields ECHO G control variables Symbols Additional codes for ECHAM4 output 18 19 20 34 35 38 39 45 48 DKRZ ECHO G Model Documentation DKRZ ECHO G Model Documentation 1 Summary The coupled atmosphere ocean climate model ECHO G is set up from cycle 4 of the Hamburg atmo sphere general circulation model ECHAM and the global version of the Hamburg Ocean Primitive Equation general circulation model HOPE G The latter incorporates a dynamic thermodynamic sea ice model with snow cover The atmosphere model ECHAM is described in volume 6 of the DKRZ technical report series DKRZ 1993 It has been modified for ECHO G in order to properly account for a sub gridscale partial ice cover as described in Groetzner et al 1996 With these modifications heat freshwater

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