USER MANUAL AND EXERCISES - Climate Modelling Primer
Contents
1. 48 El 40 50 0 307 18 Solar Constant 05 El 20 40 20 30 10 20 0 3039 0 272 0 248 18 i223 0 10 0 204 263 OF EBM Manual 11 reset all defaults change pen color o iia EBM Manual Version 2 1 3 5 Sequence mode When graphics mode is selected you can also enable and use the sequence mode Sequence mode runs a set of simulations for a range of values of solar constant and can be useful when experimenting with different parameter values Energy Balance Model File Edit Mode View Energy Balance Model Initial conditions O Present day Model parameters C follow on initial conditions O Glaciated Edit albedo of ice Ice free albedos Mean global temperature in 0 5 Celsius 05 100 0 452 0 407 0 357 0 309 Edit critical temp Edit value for C Edit value for 4 0 272 eo Edit value for B 0 248 l 0 254 5 log file san Fraction of present day solar constant userid Canada Latitude Albedo Temperat Global mean temperature 33 9 80 90 O62 44 9 20 80 0 62 EN iese al defaults _ o ae Sol Constant a Ao E Run sequence add text to log 30 40 0 62 ie o LA E Ci s Caewate eg gt 0 10 0 52 EBM Manual 12 EBM Manual EBM Manual v2 1 3 6 Help Instructions dialog The instructions box does not currently function in Windows In future versions it m2. 89 54 36279 204 2 17 3 8 0 62 10 916 56 53 76209 204 2 17 3 8 0 62 10 930 24 53 16139 204 2 17 3 8 0 62 10 943 92 52 56068 204 2 17 3 8 0 62 10 957 6 51 95998 204 2 17 3 8 0 62 10 971 28 51 35928 204 2 17 3 8 0 62 10 994 96 50 75957 204 2 17 3 8 0 62 10 998 64 50 15787 204 2 17 3 8 0 62 10 1012 32 49 55717 4 Use the refresh button to update the screen if need be The log file cannot be stopped but you can start a new log file at any time effectively closing off the first one If you use the same name the file will be overwritten f Excel File Edit View Insert Format Tools Data Window Help al gt E rn m E z r gt o BB BS eg o Ly fe y sE OS E 100 lv 2 gt als 3 BP zEIB A hr es Verdana Mhio Meg 7 ul 80098 S logdemo01 csv A B c D E F G HA 4A A EBM output file gt T 2 Sunday 4 September 2005 at 1 52 13 PM 3 Created by 4 Filename logdemo01 csv 5 Results output below in the following order 6 Aice Terit SolconGlobalMeanT 7 204 2 17 3 8 0 62 10 1368 15 28891 8 new text added 9 204 2 17 3 8 0 62 10 752 4 60 97053 204 2 17 3 8 0 62 10 766 08 60 36983 EBM Results Seriesl Global mean temperature 70 Solar Constant 204 2 17 3 8 0 62 10 1162 8 4 341801 204 2 17 3 8 0 62 10 1176 48 3 28689 204 2 17 3 8 0 62 10 1190 16 2 231979 204 2 17 3 8 0 62 10 1203 84 1 177068 2
3. 04 2 17 3 8 0 62 10 1217 52 2 181292 204 2 17 3 8 0 62 10 1231 2 3 262084 204 2 17 3 8 0 62 10 1244 88 4 342876 EBM Manual 9 EBM Manual Version 2 1 3 3 Expert mode When you are more familiar with the model an expert mode allows changes to be made to all of the model parameters This expert mode can be enabled by selecting expert from the file menu Additional edit fields appear on the right and the albedo fields on the left become editable Parameters can only be changed within a range of plausible values If you choose a value that is either implausible or outside a predefined range the model will alert you with a small red oval beside the problem value and reset it to the default value Unreasonable values can cause the model computations to become unstable hence the range of values has been limited Energy Balance Model File Edit Mode View Energy Balance Model Initial conditions Present day Model parameters C follow on initial conditions O Glaciated Edbalbeda chica Ice free albedos Edit critical temp 05 0 452 007 0 357 0 309 Edit value for C Edit value for 4 0 272 h 1 Edit value for B 0 248 l 0 254 logfile sanat cs userid a and dose Latitude Albedo Temperat Global mean temperature 45 3 80 30 0 62 13 5 i 0 90 0 62 12 9 reset all defaults A E 50 60 0 407 118 Solar Constant FL STE ee 20 30 0 272 ok Calculate EL n
4. Energy Balance Model File Edit Mode View EBM Manual v2 1 Energy Balance Mode Initial conditions C follow on initial conditions Glaciated Ice free albedos Mean global temperature in 0 5 80 30 Celsius 05 70 80 100 0 452 60 70 0 407 5050 0 357 40 50 10 309 3040 0 272 20 30 0 248 10 20 10 254 040 50 O Present day Model parameters Edit albedo of ice 0 62 Edit criticaltemp 10 reset Edit value for C Edit value for 4 Edit value for B reset Latitude Albedo Temperat 80 90 D 44 9 70 80 l 442 42 2 1 39 i 36 3 33 5 31 4 E i h 5 log file Fraction of present day solar constant userid Global mean temperature 33 9 reset all defaults change pen color o Sl Cor rola USER MANUAL AND EXERCISES EBM Manual EBM Manual Version 2 1 Version information Date 4 Sept 05 5 Sept 05 9 June 2006 Initial draft Beta draft for circulation with version 2 0 of EBM Version 2 0 has log files which can be saved for later analysis in a spreadsheet Used at UTS Version 2 1 of the EBM includes a fix for a couple of minor bugs and a fix for a bug which made the model abend due to an address bounds exception Included an untested Linux version in the distribution for the first time The manual was updated only to change the 2 0 to 2 1 Made with pg REALbasic EBM Manual EBM Manual v2 1 EBM v2 0 Manual ccccc
5. albedo is set to 0 62 The solar constant in the model is taken as 1370 Wm The EBM is designed to be used to examine the sensitivity of the predicted equilibrium climate to changes in the solar constant If the default values for the variables A B K and the albedo formulation are selected an equilibrium climate which is quite close to the present day situation is predicted for a fraction 1 of the solar constant This equilibrium climate is given when the model starts Once this equilibrium value for an unchanged solar constant has been seen the user can modify the fraction of the solar constant prescribed and note the changes in the predicted climate More importantly the EBM permits the user to alter the albedo formulation the latitudinal transport and the parameters in the infrared radiation term and examine the sensitivity of the modified model The EBM is presented here in a hemispheric form In the program an equilibrium solution is achieved by iterating the calculation of each zonal T of equation 3 13 A maximum of 50 iterations is allowed and since convergence is usually achieved after only two or three iterations more than 50 iterations indicates that the calculation has failed The snow free albedo of the planet has been coded as latitude dependent Remember that this is the snow free planetary albedo We include the effects of clouds in these numbers EBM Manual Version 2 1 2 2 Starting the EBM The model is current
6. ay contain customisable instructions and exercises Instructions Exercises 13 EBM Manual Version 2 1 4 EBM Exercises Take some time to work through the exercises below They are useful examples of the types of climate simulation experiments that can be undertaken 4 1 Snowball Earth Exercise 1 a Using the default values of set in the program determine what decrease in the solar constant is required just to glaciate the Earth completely Adjust the solar constant using the slider and press the calculate button At this stage just observe the ice indicated by the albedo value of 0 62 in the table b Now make the model a little more realistic by making the model use the results from its simulation as initial conditions for the next run Once the ice covers the Earth how much increase in solar constant is required to break free of this snowball Earth state EBM Manual 14 EBM Manual v2 1 100 100 0 5 1 1 5 EBM Manual 15 EBM Manual Version 2 1 4 2 Atmospheric and Oceanic transport You will want to switch to graphics mode and use the sequence feature in this exercise Exercise 2 a Various authors have suggested different values for the transport coefficient K C in the model used here For instance Budyko 1969 originally used K 3 81 W m2 C 1 and Warren and Schneider 1979 used K 3 74 W m2 C 1 How does chang
7. ccececeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeees 4 1 ntr duction ua 4 2 Energy Balance Climate Models eeeee 4 2 1 Quick Description of the EBM 4 3 EBM F nttionality 52 7 DF BaSiCS anna 7 3 2 TOG 01010 ai eas site ac sie in esc une ana see ARE HERE eee eee 8 33 EXPE mode a een 10 3 4 Graphics M ge cacas 11 3 5 Sequence mode es 12 3 6 Help Instructions dialog eee 13 4 EBM EXeIrciseS ioc cae eet 14 4 1 Snowball BAM Ma aaa et 14 4 2 Atmospheric and Oceanic transport 16 4 3 Further Exercises cccccccceccecessseseeeeeeeeeees 18 EBM Manual 3 EBM Manual Version 2 1 EBM v2 1 Manual 1 Introduction This manual contains information about Version 2 of the Energy Balance Model from A Climate Modelling Primer The manual contains a description of the fundamentals of energy balance models Section 2 and describes how to get answers from this very simple implementation of a climate model Section 3 Section 4 includes some simple exercises that could be used in a class or for self directed study 2 Energy Balance Climate Models This type of climate model is a useful teaching learning tool The program was originally written for undergraduate use at the University of Liverpool in the early 1980s This version has been updated to allow for increases in the performance of personal computers and a few new features have been a
8. dded that make integration into a broader learning program more feasible The formulation of the EBM here has been kept as simple as possible The equations are those described in Section 3 2 of A Climate Modelling Primer The albedo parameterization is a simple on off step function based on a specified temperature threshold The emitted longwave radiation is a linear function of the zonal surface temperature and the transport term is a simple diffusive term dependent on the difference between the zonal temperature and the mean global temperature The following sections contain a brief summary of the model presented in Figure 3 2 and suggest some exercises which demonstrate the model s behaviour 2 1 Quick Description of the EBM The model is governed by the equation originally devised by both Sellers and Budyko in 1969 Shortwave in Transport out Longwave out 3 18 which is formulated as S p 1 a p KIT T A BT 3 19 where K the transport coefficient here set equal to 3 80 W m2 C T the surface temperature at latitude q EBM Manual 4 EBM Manual EBM Manual v2 1 T the mean global surface temperature A and B are constants governing the longwave radiation loss here taking values A 204 0 W m2 and B 2 17 W m2 C S the mean annual radiation incident at a latitude a g the planetary albedo at latitude Note that if the surface temperature at is less than 10 C the
9. ed as show above to remind you where to find your results The log file cannot be turned off until the program is closed by selecting quit from the file menu or program menu for Macintosh users The figure below shows the logbook window after a few calculations have been made using the sequence button You can use the add text to log button to add comments to your log file amp add text Enter text to add to the log file useful for making notes Enter text so you can add comments to your log file The log file can be checked by clicking the view log file button A sample view of a typical log file is shown below This can be readily imported into a spreadsheet as illustrated EBM Manual 8 EBM Manual v2 1 EBM Logbook These are the numbers computed during your entire session with the EBM This is your chance to save the numbers to a file suitable for importing into a spreadsheet EBM output file Sunday 4 September 2005 at 2 10 46 PM Created by Carol and Jose Filename sample01 csv Results output below in the following order 4 B C Aice Terit SolconGlobalMeanT 204 2 17 3 8 0 62 10 752 4 60 97053 204 2 17 3 8 0 62 10 766 08 60 36983 204 2 17 3 8 0 62 10 779 76 59 76912 204 2 17 3 8 0 62 10 793 44 59 16842 204 2 17 3 8 0 62 10 807 12 58 56772 204 2 17 3 8 0 62 10 820 8 57 96701 204 2 17 3 8 0 62 10 834 48 57 36631 204 2 17 3 8 0 62 10 889 2 54 9635 204 2 17 3 8 0 62 10 902
10. here have been many suggestions for the values of the constants A and B determining the longwave emission from the planet some have been dependent on cloud amount Budyko 1969 originally used A 202 W m 2 and B 1 45 W m2 C 1 Cess 1976 suggested A 212 W m 2 and B 1 6 W m 2 C 1 How do these different constants influence the climate and its sensitivity b Holding A constant just vary B and investigate the effect on the climate What does a variation of B correspond to physically EBM Manual 18 EBM Manual v2 1 EBM Manual 19
11. ing the value of C affect the model climate and climate sensitivity b Investigate the climate that results when using very small or very large values of K How sensitive are these different climates to changes in the solar constant Try and predict how you think the model will behave before you perform the experiment EBM Manual 16 EBM Manual v2 1 100 100 EBM Manual 17 EBM Manual Version 2 1 4 3 Further Exercises This simple model can be manipulated further to simulate changes caused by continental configuration and in vegetation snow masking and cloud cover Try these exercises Exercise 3 a Observations show that land will be totally snow covered during winter for an annual mean surface temperature of 0 C and oceans totally ice covered all year for a temperature of about 13 C The model specifies a change from land sea to snow ice at 10 C appropriate for a land distribution similar to today s Alter this critical temperature and investigate the change in the climate and the climatic sensitivity around present day solar constant to changing the solar radiation input b The albedo over snow covered areas can vary within the limits of 0 5 0 8 depending on vegetation type cloud cover and snow ice condition Investigate the sensitivity of the simulated climate and climate sensitivity to changing the snow ice albedo Exercise 4 a T
12. isible when you first open the application 1 The value for the solar constant can be changed using the slider or more finely by the small arrows on the right of the slider ii When the calculate button is pressed the model displays the resulting global mean temperature in the text field and updates the zonal climates accordingly iii Default values for parameters and for the solar constant can be reset using the reset all defaults button Further aspects of the model can be changed as the various modes of the model are activated as described below EBM Manual 7 EBM Manual Version 2 1 3 2 Logbook The EBM can save results to a log file for later analysis and plotting in MS Excel or similar package To open a log file choose open a log file from the file menu and complete the fields in the dialog box below S Open a log file filename 2 gt Choose a name 6 8 characters for your log file If the log file file already exists your results will be appended to this i gt 4 userid file 15 3 Example alison01 cd A y reset all defaults This will results in a file called alison01 csw that can be read into MS Excel add text to log a Choose a filename for your file it will be saved as a csv file and add an optional user ID to assist in identifying the file The filename will be displayed in the main window when the log file is active The log file name and user ID are display
13. ly made for Windows XP 2000 and for Macintosh OSX Linux builds and Macintosh Classic versions are included in the distribution but have no way to test these versions so who knows how well they work The images in this document are for Windows based computers but the layout should be the same for all systems To start the model double click on the EBM2 0 exe file The EBM screen should appears as below Energy Balance Model File Edit Mode View Energy Balance Model C follow on initial conditions Ice free albedos 05 05 042 0 407 0 357 0309 0 272 0 248 O24 No log file in use Latitude Albedo Temperat Global mean temperature 453 80 90 0 62 235 i 70 80 0 62 SECM 60 70 0 452 40 i 50 50 0 407 1 8 i e Solar Constant 40 50 0 357 00 E 0 309 i 0 248 269 i v 0 204 TA EBM Manual 6 EBM Manual v2 1 3 EBM Functionality 3 1 Basics Energy Balance Model File Edit Mode View Energy Balance Model C follow on initial conditions Ice free albedos No log file in use Latitude Albedo Temperat Global mean temperature 15 3 70 80 0 62 12 60 70 0 452 fA i 50 60 0 407 i Solar Constant 40 50 0 354 iS E 30 40 0 303 i i 20 30 0 272 i223 i Calculate 10 20 0 248 26 9 0 10 0 254 ret E The EBM is a very simple application A few simple things are v
14. r __Catcutate O10 0264377 EBM Manual 10 3 4 Graphics mode EBM Manual v2 1 The colour image can be replaced by a graph that plots the mean global temperature as a function of solar constant as values are computed by the user Select graphics in the mode menu to activate the graphics canvas Users can change the colour of the pen selected at random each click and can clear the canvas by pressing the clear button When graphics mode is activated the screen looks like the one presented below At the moment there is not a way to copy the graphics from the canvas into another document If you wish to save the picture created use ALT PRTSCRN on Windows machines and the Grab program on Macs Energy Balance Model File Edit Mode View Energy Balance Model Ice free albedos 0 5 0 357 05 0 452 0407 5060 0 309 0 272 0 248 0 254 80 90 70 80 60 70 40 50 30 40 20 30 10 20 0 10 Present day C follow on initial conditions O Glaciated Mean global temperature in Celsius 100 50 reset Initial conditions Model parameters Edit albedo of ice Edit critical temp Edit value for C Edit value for 4 Edit value for B 5 log file Fraction of present day solar constant userid Latitude 80 90 0 80 60 70 50 60 Albedo 0 62 0 62 0 452 0 407 Temperat Global mean temperature 153 1 135 E L led
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