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Product User Manual for “Cloud Products”

1. Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MEL SCI PUM 01 METEOTRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MFL SCI PUM 01_v3 2 v2 2 Page 1 32 The EUMETSAT Network of Sateiiie Application Fociities Support lo Nowcasting and Very Short Range Forecasting Product User Manual for Cloud Products CMa PGE01 v3 2 CT PGE02 v2 2 amp CTTH PGE03 v2 2 SAF NWC CDOP MFL SCI PUM 01 Issue 3 Rev 2 15 February 2012 Applicable to SAFNWC MSG version 2012 Prepared by M t o France Centre de M t orologie Spatiale Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MEL SCI PUM 01 TEO F P METEO FRANCE PGE02 v2 2 amp CTTH PGEO3 Issue 1a Date eee NWC SAF File SAF NWC CDOP MFL SCI PUM 01_v3 2 v2 2 Page 2 32 REPORT SIGNATURE TABLE Marcel Derrien Prepared by MF DP CMS Herv Le Gl au MF DP CMS Reviewed by Authorised by Pilar Fernandez SAFNWC Project Manager 15 February 2012 15 February 2012 Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MEL SCI PUM 01 METEO FRANCE P Toujours un temps d avance PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MFL SCI PUM 01_v3 2 v2 2 Page 3 32 DOCUMENT CHANGE RECORD CHANGE S 7 November 2
2. More than one bit may be activated if tests were not really successful measurement too close to thresholds 0 T10 8um or SST RO 6um land or RO 8um sea Sunglint test using 3 9um Local Spatial Texture T10 8um T12 0um T10 8um T3 9um or T12 0um T3 9um T3 9um T10 8um Spatial smoothing reclassify isolated cloud free pixels T8 7um T3 9um R1 6um sea T8 7um T10 8um or T10 8um T8 7um Snow using R1 6um or T3 9um HRV based test Stationary cloud in twilight Spatial expansion of stationary cloud in twilight Temporal differencing D IN 1 R D Re nu e ODO Un D e 11 bits for quality 3 bits to define illumination and viewing conditions Undefined space Night Twilight Day Sunglint bits to describe NWP input data Undefined space All NWP parameters available no low level inversion All NWP parameters available low level inversion At least one NWP parameter missing WNrRONMN RS DH Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METEOTRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEFL SCI PUM 01_v3 2 v2 2 Page 12 32 2 bits to describe SEVIRI input data 0 Undefined space 1 All useful SEVIRI channels available 2 At least one useful SEVIRI channel missing 3 A least one mandatory SEVIRI channel missing 2 bits to describe the quality of the p
3. the tests that have allowed the cloud detection more that one test are possible if some tests were not really successful are stored Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MEL SCI PUM 01 TEO FRAN METEO ERANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MFL SCI PUM 01_v3 2 v2 2 Page 10 32 A second process allowing the identification of dust clouds and volcanic ash clouds is applied to all pixels even already classified as cloud free or contaminated by clouds The result is stored in the dust cloud and volcanic ash cloud flags Details on the tests are given in the algorithm theoretical basis document for cloud products AD 4 Twilight Nighttime T10 8um T10 8um T10 8um T12 0um RO 6um RO 6um T8 7um T10 8um a A E as T8 7um T3 9um Table 3 Test sequence over land T10 8um T3 9um T10 8um T3 9um T10 8um T3 9um Local Spatial Texture T3 9um T10 8um Low Clouds in Sunglint T12 0um T3 9um T8 7um T10 8um RO 8um R0 6um T8 7um T10 8um T3 9um T10 8um T3 9um T8 7um T10 8um and T12 0um stand for brightness temperatures at 3 9 8 7 10 8 and 12 0 micrometer RO 6um RO 8um and R1 6um stand for VIS NIR bi directional top of atmosphere reflectances at 0 6 0 8 and 1 6 micrometer normalised for solar illumination SST is the split window used for SST calculation computed from T10 8um and T12 0um measureme
4. 01_v3 2 v2 2 Page 26 32 basis is that clouds have a stronger impact in a window channel than in a sounding channel The following process is implemented e The H O IRW intercept method based on a window 10 8um and sounding 13 4um 7 3m or 6 2um radiance bi dimensional histogram analysis is first applied The histograms are built in boxes of 32 32 SEVIRI IR pixels centred on each segment of the image whose size is defined by the user the default value being 16 16 SEVIRI IR pixels It therefore allows the retrieval of cloud top pressure at the segment horizontal resolution i e by default 16 16 SEVIRI IR pixels This method is successively applied using the 7 3um 6 2um and 13 4um radiances the final retrieved cloud pressure being the minimum cloud top pressures obtained using single sounding channels e If no result can be obtained with the HO IRW intercept method the radiance ratioing method is then applied to the 10 8um and 7 3um radiances to retrieve the cloud top pressure at a pixel basis If no result can be obtained the method is applied to 6 2um and finally to 13 4um radiances e If the radiance ratioing technique leads to cloud top temperatures warmer than the corresponding 10 8um brightness temperatures the method for thick clouds is used instead e For fractional clouds No technique is proposed in the current version for low broken clouds The sounding channels are nearly unaffected by broken low clouds and are
5. 2 Page 30 32 The following SEVIRI brightness temperatures and radiances are needed at full IR spatial resolution Rad6 2um Rad7 3um Rad13 4um Rad10 8um At least one of these channels is mandatory Mandatory Mandatory Optional the two others are then optional The CTTH software checks the availability of SEVIRI brightness temperatures and radiances for each pixel Full CTTH product is computed only if all mandatory SEVIRI radiances and brightness temperatures are available If T10 8um brightness temperature is missing no result is available If T10 8um brightness temperature is available but mandatory channels are missing only the cloud top temperature is computed using the method based on climatological atmospheric absorption correction The SEVIRI channels are input by the user in HRIT format and extracted on the processed region by SAFNWC software package e CMa and CT cloud categories The CMa and CT cloud categories are mandatory They are computed by the CMa and CT software e Satellite angles associated to SEVIRI imagery This information is mandatory It is computed by the CTTH software itself using the definition of the region and the satellite characteristics e NWP parameters The forecast fields of the following parameters remapped onto satellite images are used as input o surface temperature surface pressure air temperature and relative humidity alternatively dew point temperature at 2m air
6. SAF File SAF NWC CDOP MFL SCI PUM 01_v3 2 v2 2 Page 17132 Example of visualisation of the dust cloud and the volcanic ash cloud flags superimposed on infrared images are given in Figure 1 and Figure 2 using SEVIRI and MODIS imagery dust cloud 20C 10C oc 10C 20C 30C Figure 1 Example of SEVIRI dust cloud flag superimposed on a 10 8 um infrared image dust cloud over North Africa on 14 July 2003 at 13h00 UTC kz volcanic ash 40C 35C 30C 25C 20C 15C 10C 5C oc Figure 2 Example of MODIS volcanic ash cloud superimposed on a 10 8 um infrared image Etna eruption on 22th July 2001 at 9h55 UTC Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METEO FRANCE 5 4502 v2 2 amp CTTH PGE03 __ Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEL SCI PUM 01_v3 2 v2 2 Page 18 32 3 CLOUD TYPE CT PRODUCT 3 1 DESCRIPTION OF CLOUD TYPE CT PRODUCT 3 1 1 Goal of Cloud Type CT product The cloud type CT developed within the SAF NWC context mainly aims to support nowcasting applications The main objective of this product is to provide a detailed cloud analysis It may be used as input to an objective meso scale analysis which in turn may feed a simple nowcasting scheme as an intermediate product input to other products or as a final image product for display at a forecaster s desk The CT product is e
7. SAF NWC SAF on support to NoWCasting and VSRF SAF OSI Ocean and Sea Ice SAF SEVIRI Spinning Enhanced Visible amp Infrared Imager SW Software Tilum 11 micrometer infrared brightness temperature 1 6 REFERENCES 1 6 1 Applicable Documents Reference Title Code Vers Date AD 1 Interface Control Document for the External SAF NWC IOP INM SW ICD 1 2 0 and Internal Interfaces of the SAFNWC MSG AD 2 SAFNWC MSG Output Products Format SAF NWC IOP INM SW ICD 3 2 0 Definition AD 3 Software User Manual for the SAFNWC MSG SAF NWC IOP INM SW SUM 2 2 0 application AD 4 Algorithm Theoretical Basis Document for SAF NWC CDOP MFL SCI ATB 3 2 15 02 12 Cloud Products CMa PGEO1 v3 2 CT D 01 PGE02 v2 2 amp CTTH PGE03 v2 2 AD 5 Validation Report for Cloud Products CMa SAF NWC CDOP MFL SCI VR 06 1 0 15 02 12 PGEO1 v3 2 CT PGE02 v2 2 amp CTTH PGE03 v2 2 Table 1 List of Applicable Documents 1 6 2 Reference Documents RD S T Ef RDA Table 2 List of Referenced Documents Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METEO ee PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEFL SCI PUM 01_v3 2 v2 2 Page 9 32 2 CLOUD MASK CMA PRODUCT 2 1 DESCRIPTION OF CLOUD MASK CMA PRODUCT 2 1 1 Goal of Cloud Mask CMa product The cloud mask CMa developed within the SAF NWC context aims to
8. Short Range Forecasting SAFNWC The main objective of SAFNWC is to provide further develop and maintain software packages to be used for Nowcasting applications of operational meteorological satellite data by National Meteorological Services More information can be found at the SAFNWC webpage http nwcsaf org This document is applicable to the SAFNWC processing package for Meteosat Second Generation satellites SAFNWC MSG 1 1 SCOPE OF THE DOCUMENT This document is the Product User Manual for MSG cloud products PGEO1 CMa PGEO02 CT and PGE03 CTTH This document contains practical information on the characteristics of the above mentioned products on their applicability and limitations 1 2 SCOPE OF OTHER DOCUMENTS The algorithms used to extract the MSG Cloud Products PGEO1 CMa PGE02 CT and PGE03 CTTH are detailed in the algorithm theoretical basis document for cloud products AD 4 The validation of the algorithms used to extract the MSG Cloud Products PGEO1 CMa PGE02 CT and PGE03 CTTH is reported in the validation report for cloud products AD 5 Instructions to install configure and execute the SAFNWC MSG software in order to extract the MSG Cloud Products PGEO1 CMa PGE02 CT and PGE03 CTTH are detailed in the software user manual AD 3 The interface control documents AD 1 for the External and Internal Interfaces of the SAFNWC MSG and AD 2 MSG Output Product Format Definition deta
9. example the replacement of a snowy area by a low cloud between two successive pictures may be due only to the transition from day to night as the snow detection is not possible at nighttime broken sem above sem thick gem med sem thin very high vary high cum high high cum low cum very low very law cum seg ice land snow gea land noproc included in CT HDF files B i LM x colour palette as Figure 3 Example of SEVIRI CT cloud type using the M Cloud Phase flag undefined ice watar i naproc aN ji sg 4 Fi p a x re RE ae i Z ns ane a t FE O 7 Figure 4 Example of SEVIRI CT cloud phase using the colour palette included in CT HDF files Sa 4 xe pE PM ANDS DE Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 T A A METEO TRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEL SCI PUM 01_v3 2 v2 2 Page 25 32 4 CLOUD TOP TEMPERATURE AND HEIGHT CTTH PRODUCT 4 1 DESCRIPTION OF CLOUD TOP TEMPERATURE AND HEIGHT CTTH PRODUCT 4 1 1 Goal of Cloud Top Temperature and Height CTTH product The cloud top temperature and height CTTH developed within the SAF NWC context aims to support nowcasting applications This product contributes to the analysis and early warning of thunderstorm development Other applications inc
10. refer to paragraph 2 4 e Very thin cirrus are often classified as fractional clouds e Very low clouds may be classified as medium clouds in case strong thermal inversion e Low clouds surmounted by thin cirrus may be classified as medium clouds 3 5 EXAMPLE OF CLOUD TYPE CT VISUALISATION It is important to note that the CT product is not just an image but numerical data At first hand the CT is rather thought to be used digitally together with the appended flags quality cloud phase as input to mesoscale analysis models objective Nowcasting schemes but also in the extraction of other SAFNWC products CTTH for example Colour palettes are included in CT HDF files thus allowing an easy visualisation of CT cloud type categories as illustrated on Figure 3 Product User Manual for Cloud Products CMa PGE01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 ME PGEO2v2 2 amp CTTH PGEO3 _ Issue 22 Date rare NWC SAF 5 5 File SAF NWC CDOP MEFL SCI PUM 01_v3 2 v2 2 Page 24 32 The user may be interested in visualising all the available classes please keep in mind that the separation between stratiform and cumuliform clouds is not performed in the current CT version as displayed on a SEVIRI example in Figure 3 or highlight one or a few categories suitable for the application of interest Product s animation will be a help for the user to interpret the visualized CT and to identify artefacts for
11. support nowcasting applications and additionally the remote sensing of continental and oceanic surfaces The CMa allows identifying cloud free areas where other products total or layer precipitable water land or sea surface temperatures snow ice cover delineation may be computed It also allows identifying cloudy areas where other products cloud types and cloud top temperature height may be derived The central aim of the CMa is therefore to delineate all cloud free pixels in a satellite scene with a high confidence In addition the product provides information on the presence of snow sea ice dust clouds and volcanic plumes 2 1 2 Outline of Cloud Mask CMa algorithm The algorithm is based on multispectral threshold technique applied to each pixel of the image A first process allows the identification of cloudy pixels It consists in a first set of multispectral threshold tests summed up below which is complemented by an analysis of the temporal variation on a short period of time 15 minutes of some spectral combinations of channels to detect rapidly moving clouds a specific treatment combining temporal coherency analysis and region growing technique to improve the detection of low clouds and a temporal analysis of the HRV channel to detect sub pixel cumulus clouds The first series of tests allows the identification of pixels contaminated by clouds or snow ice this process is stopped if one test is really successful i e if
12. temperature and relative humidity on vertical pressure levels altitude of the NWP model grid alternatively surface geopotential on the NWP model grid Required if NWP fields are used as input G O0 0 Vertical pressure levels on which air temperature and humidity are defined by the user All the surface and near surface NWP informations and at least NWP informations every 210hPa on the vertical are mandatory to get full CTTH product Otherwise only the cloud top temperature is retrieved using the method based on climatological atmospheric absorption correction Furthermore it is recommended to provide NWP information on levels at least up to 100hPa to ensure a good height retrieval quality for very high clouds These remapped fields are elaborated by the SAFNWC software package from the NWP fields input by the user in GRIB format e Ancillary data sets The following ancillary data remapped onto satellite images are mandatory o Land sea atlas o Elevation atlas o Monthly minimum SST climatology o Monthly mean 0 6um atmospheric corrected reflectance climatology land These ancillary data are available in the SAFNWC software package on MSG full disk in the default satellite projection at full IR resolution They are extracted on the processed region by the CTTH software itself Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 T A A METEOTRANCE PGE02 v2 2 amp
13. the cloud phase flag should be computed is configurable see its definition in 3 2 1 Its default value is TRUE Information on how to change this value can be found in the software user manual AD 3 and in section 3 2 1 e CT_PHASE_SZSEG The size of the segment for cloud phase flag computation is configurable see its definition in 3 2 1 Its default value is 8 Information on how to change the size of the segment can be found in the software user manual AD 3 and in section 3 2 1 3 4 CLOUD TYPE CT VALIDATION 3 4 1 Summary of Cloud Type CT validation results Table 6 summarises the validation results of the current version More details can be obtained from the validation report for cloud products AD 5 PGE02 Validated accuracy PGE02 cloud type validated over European areas and adjacent User accuracy for low opaque high opaque semi transparent high seas using interactive targets clouds between 78 and 96 depending on illumination the user accuracy is defined as the probability of a pixel being classified into a category to really belong to this category PGE02 cloud phase flag Hit Rate HR 0 83 validated over European areas using ground Kuiper Skill Score KSS 0 62 based radar lidar Table 6 Summary of validation results of the current PGEO2 version AD 5 3 4 2 Typical known problems and recommendation for use The following problems may be encountered for wrong cloud detection please
14. the threshold is not too close to the measured value The characteristics of this set of tests are summed up below e The tests applied to land or sea pixels depend on the solar illumination and on the viewing angles and are presented in Table 3 and Table 4 e Most thresholds are determined from satellite dependent look up tables available in coefficients files using as input the viewing geometry sun and satellite viewing angles NWP forecast fields surface temperature and total atmospheric water vapour content and ancillary data elevation and climatological data The thresholds are computed at a spatial resolution called segment size defined by the user as a number of SEVIRI infra red pixels Some thresholds are empirical constant or satellite dependent values available in coefficients files e The quality of the cloud detection process is assessed e A spatial filtering is applied allowing to reclassify pixels having a class type different from their neighbours and to reduce known defaults as cloud false alarms in coastal area and in edges of snowy areas e A test is applied to cloud contaminated pixels to check whether the cloud cover is opaque and completely fills the FOV This first series of tests allows to determine the cloud cover category of each pixel cloud free cloud contaminated cloud filled snow ice contaminated or undefined non processed and compute a quality flag on the processing itself Moreover
15. up the process By default this preparation step is performed during the CMa execution step The CMa execution step which includes the CMa preparation step in case it has not been launched before is automatically launched by the Task Manager if real time environment is selected Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METEO TRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEL SCI PUM 01_v3 2 v2 2 Page 13132 2 2 1 Manual preparation of Cloud Mask CMa model configuration file for each region When a new region is defined and added in system and run configuration files the user must manually prepares the CMa model configuration files by adapting the CMa default model configuration file available in the SAFNWC software package Three parameters are configurable in the default CMa model configuration file e CMA_SZSEG default value 4 the size of the segment for CMa The new segment size must also be updated in the lines NWP_PARAMxx Segments are square boxes in the satellite projection whose size is expressed as the number of IR pixels of one edge of the square box The size of the processed regions must be a multiple of the segment size All the solar and satellite angles the NWP model forecast values the atlas values and the thresholds will be derived over all the processed regions at the horizontal r
16. 007 30 Initial version content derived from User manual for PGEO1 02 03 v1 3 Cloud Products of the SAFNWC MSG scientific part 23 August 2008 Content adapted to version v2 0 17 may 2010 Content adapted to version v3 0 1 4 2 0 i 3 0 i f 24 march 2011 Content adapted to version v3 1 15 February 2012 Content adapted to version v3 2 Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METEO TRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MFL SCI PUM 01_v3 2 v2 2 Page 4 32 Table of contents 1 INTRODUCTION scsi 7 Li SCOPE OF THE DOCUMEN T irisiiisriicaiicadisadidaiicndidaiicndidaiiaadii aiaiai aiaiai iaaiiai 7 1 2 SCOPE OF OTHER DOCUMENTS nent bebe sy sy aedeaudesetesatatatsbsdenedeertvavivavsusetonnteretenetesese 7 1 3 SOFTWARE VERSION IDENTIFICATION nn ns sl in iatis 7 1 4 IMPROVEMENT FROM PREVIOUS VERSION ccescsssssceessceeeseceessceeessceceseeeesseeeesseecesaeessneeeseeeeees 7 1 5 DEFINITIONS ACRONYMS AND ABBREVIATIONS users 7 1 6 REFERENCES veias3eactacaatnatsacadeaesedeseacsssastcaenatateasedvaaegsiadharadenttnaddead aacdeaa ondSeadsnaddeedsaadhendeeaveadseaik 8 1 6 1 APPC AOLE D ONTON S a EA E UIC O VOA OO AOA OONA 8 1 6 2 Relerence DOCHINGINS esseeri erer SAAREN REE SEEEN RENSE amp 2 CLOUD MASK CMA PRODUCT sms 9 2l DESCRIPTION OF CLOUD MASK CMA PRODUCT osssrrisirireittsiitt tisis tts t t
17. CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEL SCI PUM 01_v3 2 v2 2 Page 31 32 RTTOV 9 coefficients file mandatory for RTTOV radiative transfer calculation is available in the SAFNWC software package If RTTOV model cannot be launched only the cloud top temperature is computed using the method based on climatological atmospheric absorption correction One coefficients file containing satellite dependent values and one look up table for climatological atmospheric absorption correction is available in the SAFNWC software package and is needed by the CTTH software 4 3 2 Configurable parameters for Cloud Top Temperature and Height CTTH Besides the NWP parameters to be used the levels may be changed by the user only one parameter is configurable in the default CTTH model configuration file e CTTH_SZSEG The size of the segment is configurable see its definition in 4 2 1 Its default value is 16 Information on how to change the size of the segment can be found in the software user manual AD 3 and in section 4 2 1 4 4 CLOUD TOP TEMPERATURE AND HEIGHT CTTH VALIDATION 4 4 1 Summary of Cloud Top Temperature and Height CTTH validation results Table 7 summarises the validation results of the current version More details can be obtained from the validation report for cloud products AD 5 PGE03 products Validated accuracy bias std Top height of opaque low mid level and h
18. EMPORAL_USE The flag defining if temporal information is to be used to allow a better detection of fast moving clouds and low clouds in twilight conditions is configurable see its definition in 2 2 1 Its default value is TRUE Information on how to change this value can be found in the software user manual AD 3 and in section 2 2 1 e HRVNEED The flag indicating if HRV data have to be used to allow enhanced sub pixel cumulus detection is configurable see its definition in 2 2 1 Its default value is TRUE Information on how to change this value can be found in the software user manual AD 3 and in section 2 2 1 2 4 CLOUD MASK CMA VALIDATION 2 4 1 Summary of Cloud Mask CMa validation results Table 5 summarises the validation results of the current version More details can be obtained from the validation report for cloud products AD 5 PGE01 flags Validated accuracy PGE01 cloud detection Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MEL SCI PUM 01 METEOTRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 75 February 2012 NWC SAF 22 File SAF NWC CDOP MFL SCI PUM 01_v3 2 v2 2 Page 16 32 validated over European areas using SYNOP POD 96 5 observations PGE01 dust flag POD validated over sea and Africa for solar 55 5 over sea elevation larger than 20 degrees using 58 5 over land interactive targets Table 5 Summary o
19. GURABLE PARAMETERS FOR CLOUD MASK CMA 2 3 1 List of inputs for Cloud Mask CMa The input data to the CMa algorithm are described in this section Mandatory inputs are flagged whereas the impact of missing non mandatory data on the processing are indicated e Satellite imagery The following SEVIRI bi directional reflectances or brightness temperatures of the scene to be analysed are needed at full IR spatial resolution at HRV spatial resolution for HRV T10 8um The CMa software checks the availability of SEVIRI channels for each pixel If non mandatory channels are missing for one pixel the tests using these channels are not applied or applied differently for example snow detection uses either R1 6um or T3 9um visible channel test over the ocean uses either RO 8um or RO 6um and a result is available for this pixel No results are provided for pixels where at least one mandatory channel is missing The following SEVIRI bi directional reflectances or brightness temperatures or Cma or CT of the scene analysed one hour sooner are optionally needed to improve the cloud detection in day night transition If one of them misses this improvement is not performed The following SEVIRI brightness temperatures or Cma or CT of the scene analysed 15 minutes sooner are optionally needed to improve the cloud detection of fast moving clouds If one of them misses this improvement is not performed The HRV bi directional reflectance of th
20. abled TE CODEN Dennis 10 Table 5 Summary of validation results of the current PGEO1 version POD stands for Percentage Of EE 16 Table 6 Summary of validation results of the current PGEO2 version AD 5 23 Table 7 Summary of validation results of the current PGEO3 version std stands for standard UC VIGE OM heec hese ree eae oe ee EEE r OI 31 Figure 1 Example of SEVIRI dust cloud flag superimposed on a 10 8um infrared image dust cloud over North Africa on 14 July 2003 at 13h00 UTC 17 Figure 2 Example of MODIS volcanic ash cloud superimposed on a 10 8um infrared image Etna eruption on 22th July 2001 at 9h55 UTG sssinsiaaunanananuneneninundneawass 17 Figure 3 Example of SEVIRI CT cloud type using the colour palette included in CT HDF files 24 Figure 4 Example of SEVIRI CT cloud phase using the colour palette included in CT HDF files Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 T A METEO FRANCE 5 4502 v2 2 amp CTTH PGE03 __ Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEFL SCI PUM 01_v3 2 v2 2 Page 7 32 1 INTRODUCTION The Eumetsat Satellite Application Facilities SAF are dedicated centres of excellence for processing satellite data and form an integral part of the distributed EUMETSAT Application Ground Segment http www eumetsat int This documentation is provided by the SAF on Support to Nowcasting and Very
21. as input to mesoscale analysis models objective Nowcasting schemes but also in the extraction of other SAFNWC products Colour palettes are included in CTTH HDF files thus allowing an easy visualisation of cloud top pressure as illustrated with the SEVIRI example on Figure 5 height temperature and effective cloudiness The product if used as an image on the forecaster desk may be visualized together with CT in an interactive visualisation system where individual pixel values top temperature height and pressure cloudiness may be displayed while moving the mouse over the image Figure 5 Example of SEVIRI CTTH cloud top pressure
22. atology Monthly climatology of mean air temperature at 1000hPa 850hPa 700hPa 500hPa Or Or Or These ancillary data are available in the SAFNWC software package on MSG full disk in the default satellite projection at full IR resolution They are extracted on the processed region by the CT software itself One coefficients file also called threshold table containing satellite dependent values and look up tables for thresholds is available in the SAFNWC software package and is needed by the CT software One file containing offline simulations of 0 6um and 1 6um reflectances performed for a set of four water clouds and four ice clouds using RTMOM radiative transfer model is available in the SAFNWC software package and is needed by the CT software 3 3 2 Configurable parameters for Cloud Type CT Three configurables parameters are available in the default CT model configuration file Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MEL SCI PUM 01 T A A METEOTRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEL SCI PUM 01_v3 2 v2 2 Page 23 32 e CT_SZSEG The size of the segment is configurable see its definition in 3 2 1 Its default value is 4 Information on how to change the size of the segment can be found in the software user manual AD 3 and in section 3 2 1 e PHASE_COMPUTATION The flag defining if
23. ce parameters retrieval Nevertheless as some clouds remains undetected and to account for artefacts such as shadows or aerosols the user should apply a post processing which could include the spreading of the cloud mask that should allow to detect cloud edges and mask shadows or moist areas near cloud edges the use of the cloud mask quality flag not to compute surface parameters in bad quality cloud free areas the implementation of an additional filtering based on the temporal variation around the current slot 2 5 EXAMPLE OF CLOUD MASK CMA VISUALISATION It is important to note that the CMa product is not just images but numerical data At first hand the CMa is rather thought to be used digitally together with the appended flags quality dust detection volcanic ash detection as input to mesoscale analysis models objective Nowcasting schemes but also during the extraction of other SAFNWC products CT for example Colour palettes are included in CMa HDF files allowing an easy visualisation of CMa main categories dust and volcanic ash clouds flags No example of CMa main categories s visualisation are given as it is thought that the user will be more interested to visualize the CT product which can be seen as a refinement Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MEL SCI PUM 01 METEO FRANCE 5 4502 v2 2 amp CTTH PGEO3 Issue 3 2 Date 15 February 2012 NWC
24. clouds but contamination by thin dust volcanic clouds not checked land contaminated by snow sea contaminated by snow ice very low and cumuliform clouds very low and stratiform clouds low and cumuliform clouds low and stratiform clouds medium and cumuliform clouds medium and stratiform clouds high opaque and cumuliform clouds high opaque and stratiform clouds very high opaque and cumuliform clouds very high opaque and stratiform clouds high semitransparent thin clouds high semitransparent meanly thick clouds high semitransparent thick clouds high semitransparent above low or medium clouds fractional clouds sub pixel water clouds undefined undefined by CMa In the current version of CT the separation between cumuliform and stratiform is not performed low medium or high clouds will be classified as stratiform and a specific bit indicating whether the separation between stratiform and cumuliform clouds has been attempted will be set to zero see below quality flag e 10 bits for quality 3 bits to define illumination and viewing conditions RP SD RON UNPON UNA CON RS D nm bit Undefined space Night Twilight Day Sunglint bits to describe NWP input data Undefined space All NWP parameters available no low level inversion All NWP parameters available low level inversion At least one NWP parameter missing bits to describe SEVIRI input data Undefined space All useful SEVIRI channels available At
25. d on a pixel basis and corresponds to the best fit between the simulated and the measured 10 8um brightness temperatures The simulated brightness temperature are available at the segment resolution In case of the presence of a low level thermal inversion in the forecast NWP fields the very low low or medium clouds are assumed to be above the thermal inversion only if their brightness temperatures are colder than the air temperature below the thermal inversion minus an offset whose value depends on the nature of thermal inversion dry air above the inversion level or not e For high thick clouds a method called the radiance ratioing method see the next bullet for further explanation of this method is first applied to remove any remaining semi transparency that could have been undetected by the cloud type scheme In case of failure the method defined for medium opaque clouds is then applied e For high semi transparent clouds The 10 8um infrared brightness temperatures are contaminated by the underlying surfaces and cannot be used as for opaque clouds A correction of semi transparency is applied which requires the use of two infrared channels a window 10 8um and a sounder 13 4um 7 3um or 6 2um channels The Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METEOTRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEL SCI PUM
26. e cloud top pressure and height are not retrieved More details can be found in the algorithm theoretical basis document for cloud products AD 4 4 1 3 Description of Cloud Top Temperature and Height CTTH output The description of CTTH output in HDF format is detailed in the output products format definition document AD 2 This section summarizes the CTTH output fields a colour palette is also included in the HDF output CTTH file for each field see 4 5 e 6 bits for the cloud top pressure Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METEO FRANCE 502 v2 2 amp CTTH PGE03 _ Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEL SCI PUM 01_v3 2 v2 2 Page 27 32 Linear conversion from count to pressure Cloud_ Pressure gain Countgpits intercept corresponds to pressures ranging between Cloud_Pressure and Cloud_Pressure 25hPa Intercept Special count 15 APa Gount 250hPa e 7 bits for the cloud top height Linear conversion from count to height Cloud_Height gain Count intercept corresponds to heights ranging between Cloud_Height and Cloud_Height 200m Intercept Special count 200 m count 2000 m e 8 bits for the cloud top temperature Linear conversion from count to temperature Cloud_Temperature gain Countgpits intercept corresponds to temperatures ranging between Cloud_Temperature and Cloud_Tem
27. e scene analysed 15 minutes sooner are optionally needed to improve the sub pixel cumulus cloud detection If not available this improvement is not a The SEVIRI channels are input by the user in HRIT format and extracted on the processed region by SAFNWC software package e Sun and satellite angles associated to SEVIRI imagery This information is mandatory It is computed by the CMa software itself using the definition of the region and the satellite characteristics e NWP parameters The forecast fields of the following parameters remapped onto satellite images are used as input o surface temperatures required to get good quality results over land but not mandatory o air temperature at 950hPa alternatively 925hPa Used to check low level inversion o total water vapour content of the atmosphere o altitude of the NWP model grid alternatively surface geopotential on the NWP model grid Required if NWP fields are used as input Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 T METEO FRANCE 5 4502 v2 2 amp CTTH PGE03 __ Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MFL SCI PUM 01_v3 2 v2 2 Page 15 32 These remapped fields are elaborated by the SAFNWC software package from the NWP fields input by the user in GRIB format The NWP fields are not mandatory the CMa software replaces missing NWP surface temperatures or total wate
28. ection whose size is expressed as the number of IR pixels of one edge of the square box The size of the processed regions must be a multiple of the segment size The simulated RO 6um and R1 6um cloud reflectances for various clouds used during the processing are computed at the segment resolution The cloud phase flag quality is not very much dependent on the segment size Moreover as the content of NWP_CONF_FILE is dependent on the local installation the user must make the NWP PARAMXX consistent with the local NWP_CONF FILE when the standard one is not used for details see section dedicated to NWP data files in SAF NWC CDOP INM SW SUM 2 AD 3 3 2 2 The Cloud Type CT preparation step optional By default this CT preparation step is performed during the CT execution step see 3 2 3 But to speed up the CT processing this preparation step can performed by the command mfcms_next_pge02 which can be launched in advance of satellite data reception according to a pre defined time scheduling to be manually set by the user This preparation step includes the computation on the region at the segment spatial resolution of the solar amp satellite angles the monthly climatological amp atlas maps the thresholds for the CT algorithm the simulated RO 6um and R1 6um cloudy reflectances 3 2 3 The Cloud Type CT execution step The CT execution step which by default includes the CT preparation step see 3 2 2 is the real time proce
29. er has now to manually prepare the CT model configuration files for this new region using a default CT model configuration file provided in the SAFNWC MSG software package There is an option for the user to monitor the so called CT preparation step before SEVIRI images are available to speed up the process By default this preparation step is performed during the CT execution step The CT execution step which includes the CT preparation step in case it has not been launched before is automatically launched by the Task Manager if real time environment is selected 3 2 1 Manual preparation of Cloud Type CT model configuration file for each region When a new region is defined and added in system and run configuration files the user must manually prepares the CT model configuration files by adapting the default CT model configuration file available in the SAFNWC software package Three parameters are configurable in the default CT model configuration file e CT_SZSEG default value 4 the size of the segment This default value may be manually changed but must be the same as for CMa CMA_SZSEG The new segment size must also updated in the lines NWP_PARAMxx Segments are square boxes in the satellite projection whose size is expressed as the number of IR pixels of one edge of the square box The size of the processed regions must be a multiple of the segment size All the solar and satellite angles the NWP model forecast values
30. esolution of the segment Note also that the land sea atlas will be available at the full IR resolution allowing the identification of the surface type land or sea of all IR pixels whatever the segment size The quality is not very much dependent of the segment size if lower than 4 A segment size of 4 allows the preparation step to be 9 times faster than if a segment size of 1 was used e TEMPORAL_USE default value TRUE a flag defining if the temporal analysis should be done TEMPORAL_USE flag is checked at the execution step PGEO1 applies the temporal analysis if its value is TRUE This flag has been made configurable to allow users being blocked by hardware resources to still run the PGEO1 by assigning it to FALSE in the configuration file e HRV_NEED default value TRUE a flag indicating whether the HRV analysis should be done HRV_NEED flag is checked at the execution step PGEO1 applies the HRV analysis if its value is TRUE This flag has been made configurable to allow users being blocked by hardware resources to still run the PGEO1 by assigning it to FALSE in the configuration file When required and when the 2 HRV images required by the algorihm are not available the PGEO1 is processed without this enhancement For regions being partially covered by HRV measurements only the SEVIRI pixels having HRV benefit from enhancement Moreover as the content of NWP_CONF FILE is dependent on the local installation the user must make t
31. essing this preparation step can performed by the command mfcms_next_pge03 which can be launched in advance of satellite data reception according to a pre defined time scheduling to be manually set by the user This preparation step includes the computation on the region at the segment spatial resolution of e the solar amp satellite angles e the monthly climatological amp atlas maps e the simulated cloud free amp opaque cloud radiances with RTTOV 4 2 3 The Cloud Top Temperature and Height CTTH execution step The CTTH execution step which by default includes the CTTH preparation step see 4 2 2 is the real time processing of the SEVIRI images itself over the region This process consists in the launch of the command PGEO03 by the Task manager The CTHT is then performed using the simulated radiances prepared during the preparation step 4 3 INPUTS AND CONFIGURABLE PARAMETERS FOR CLOUD TOP TEMPERATURE AND HEIGHT CTTH 4 3 1 List of inputs for Cloud Top Temperature and Height CTTH The input data to the CTTH algorithm are described in this section Mandatory inputs are flagged whereas the impact of missing non mandatory data on the processing are indicated e Satellite imagery Product User Manual for Cloud Products CMa PGE01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METEO FRANCE 5 4502 v2 2 amp CTTH PGE03 __ Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEL SCI PUM 01_v3 2 v2
32. eter is configurable in the default CTTH model configuration file e CTTH_SZSEG default value 16 the size of the segment This default value may be manually changed independently of CMA_SZSEG and CT_SZSEG The new segment size must also updated in the lines NWP_PARAMxx Segments are square boxes in the satellite projection whose size is expressed as the number of IR pixels of one edge of the square box The size of the processed regions must be a multiple of the segment size The NWP model forecast values and RTTOV simulations will be derived over all the processed regions at the horizontal resolution of the segment A small ctth_szseg will decrease the box aspect in the retrieved cloud top pressure and will be especially useful if the NWP fields have a high horizontal resolution But it may become very time consuming as RTTOV is launched for every segment Moreover as the content of NWP_CONF_FILE is dependent on the local installation the user must make the NWP PARAMXX consistent with the local NWP CONF FILE when the standard one is not used for details see section dedicated to NWP data files in SAF NWC CDOP INM SW SUM 2 AD 3 A special attention must be payed to the consistency with the AV_PRESSURE_LEVELS of the local NWP_CONF_FILE 4 2 2 The Cloud Top Temperature and Height CTTH preparation step optional By default this CTTH preparation step is performed during the CTTH execution step see 4 2 3 But to speed up the CTTH proc
33. f validation results of the current PGEOI version POD stands for Percentage Of Detection 2 4 2 Typical known problems and recommendation for use The following problems may be encountered Low clouds may be not detected in case low solar elevation over both sea and land It may happen that large areas of low clouds are not detected in night time conditions over land This can be the case in warm sectors but also in areas viewed with high satellite zenith angles or if the low clouds are surmounted by very thin cirrus Snowy grounds are not detected at night time and therefore may confused either with low clouds or cloud free surface This drawback has been reduced with v3 1 in release2011 False detection of volcanic ash clouds happens especially in daytime conditions over low clouds and desertic surfaces but also in night time over cold clouds The volcanic ash clouds detection is not performed in case low solar elevation Over land dust cloud detection is performed only at daytime Over land dust clouds are not well detected when the sun is low or if they are too thin Over sea some dust areas may not be detected especially the thinnest parts Moreover some wrong detection may be observed in oceanic regions especially at nighttime near Namibia coast and occasionally over the South Atlantic at latitude larger than 50 degrees The CMa product may be used to identify cloud free surfaces for oceanic or continental surfa
34. g 3 at least one SEVIRI mandatory channel is missing 4 bits to describe which method has been used 0 Non processed 1 Opaque cloud using rttov 2 Opaque clouds not using rttov 3 Intercept method 10 8um 13 4um 4 Intercept method 10 8um 6 2um 5 Intercept method 10 8um 7 3um 6 Radiance Ratioing method 10 8um 13 4um il Radiance Ratioing method 10 8um 6 2um 8 Radiance Ratioing method 10 8um 7 3um 9 Spare 10 Spare 11 Spare 12 Spare 13 Opaque cloud using RTTOV in case thermal inversion 14 Spatial smoothing gap filling in semi transparent cloud field 15 Spare for not yet defined methods 2 bits to describe quality of the processing itself 0 No result Non processed cloud free no reliable method 1 Good quality high confidence 2 Poor quality low confidence 4 2 IMPLEMENTATION OF CLOUD TOP TEMPERATURE AND HEIGHT CTTH CTTH is extracted by PGE03 of the SAFNWC MSG software package Detailed information on how to run this software package is available in the software user manual AD 3 The software architecture of PGEO03 has been strongly modified in version v2010 to make the life easier for the user It is now very similar to the other PGEs In order to prepare the remapping of NWP fields by the SAFNWC software the user has to manually prepare once for ever the NWP configuration file e by defining the NWP vertical pressure levels on which he will input air temperature and relative humidity For CTTH purposes vertical levels
35. he NWP_PARAMXX consistent with the local NWP _CONF_FILE when the standard one is not used for details see section dedicated to NWP data files in SAF NWC CDOP INM SW SUM 2 AD 3 2 2 2 The Cloud Mask CMa preparation step optional By default this CMa preparation step is performed during the CMa execution step see 2 2 3 But to speed up the CMa processing this preparation step can performed by the command mfcms_next_pgeO1 which can be launched in advance of satellite data reception according to a pre defined time scheduling to be manually set by the user This preparation step includes the computation on the region at the segment spatial resolution of e the solar amp satellite angles e the monthly climatological amp atlas maps e the thresholds for the CMa algorithm 2 2 3 The Cloud Mask CMa execution step The CMa execution step which by default includes the CMa preparation step see 2 2 2 is the real time processing of the SEVIRI images itself over the region This process consists in the launch of the command PGEO1 by the Task manager The cloud masking is then performed using the thresholds prepared during the preparation step Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METEO FRANCE 5 4502 v2 2 amp CTTH PGE03 __ Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEL SCI PUM 01_v3 2 v2 2 Page 14 32 2 3 INPUTS AND CONFI
36. igh cloud validated over European areas using ground based radar lidar 120m 1050m Top height of semi transparent cloud validated over European areas using ground based radar lidar 1020m 940m intercept method 100m 1050m radiance ratioing technique Table 7 Summary of validation results of the current PGEO3 version std stands for standard deviation 4 4 2 Typical known problems and recommendation for use The following main problems may be encountered e CTTH will be wrong if the cloud is wrongly classified o Underestimation of cloud top height pressure for semi transparent clouds classified as low medium o Over estimation of cloud top height pressure for low medium clouds classified as semi transparent e No CTTH is available for clouds classified as fractional e CTTH may be not computed for thin cirrus clouds e Retrieved low cloud top height may be overestimated Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MEL SCI PUM 01 TEO FRAN METEO FRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MFL SCI PUM 01_v3 2 v2 2 Page 32 32 4 5 EXAMPLE OF CLOUD TOP TEMPERATURE AND HEIGHT CTTH VISUALISATION It is important to note that the CTTH product is not just images but numerical data At first hand the CTTH is rather thought to be used digitally together with the appended quality flags
37. il the input and output data format for the SAFNWC MSG software 1 3 SOFTWARE VERSION IDENTIFICATION This document describes the products obtained from the CMa PGE01 V3 2 CT PGE02 v2 2 and CTTH PGE03 v2 2 implemented in the release2012 of the SAFNWC MSG software package 1 4 IMPROVEMENT FROM PREVIOUS VERSION CMa CT and CTTH algorithms remain unchanged since previous version v2011 1 5 DEFINITIONS ACRONYMS AND ABBREVIATIONS CMa Cloud Mask also PGEO1 CMS Centre de Meteorologie Spatiales M t o France satellite reception centre in Lannion CTTH Cloud Top Temperature and Height CT Cloud Type ECMWF European Centre for Medium range Weather Forecast Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METEO FRANCE 14502 v2 2 amp CTTH PGEO3 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MFL SCI PUM 01_v3 2 v2 2 Page 8 32 EUMETSAT European Organisation for the Exploitation of Meteorological Satellites FOV Field Of View HDF Hierarchical data Format HRIT High Rate Information Transmission HRV High Resolution Visible ICD Interface Control Document MSG Meteosat Second Generation NWP Numerical Weather Prediction PGE Product Generation Element PUM Product User Manual RO 6um 0 6 visible reflectance RTMOM Radiative Transfer based on Matrix Operator Method RTTOV Rapid Transmissions for TOVs SAF Satellite Application Facility
38. least one useful SEVIRI channel missing At least one mandatory SEVIRI channel missing bits to describe the quality of the processing itself Non processed containing no data or corrupted data Good quality high confidence Poor quality low confidence Reclassified after spatial smoothing very low confidence set to to indicate that the separation between cumuliform and stratiform clouds has Product User Manual for Cloud Products CMa PGE01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METFOTRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEFL SCI PUM 01_v3 2 v2 2 Page 20 32 been performed In the current version of CT the separation between cumuliform and stratiform is not performed this bit will be set to zero and the low medium or high clouds will be classified as stratiform e 2 bits for cloud phase Non processed containing no data or corrupted data or no cloud water cloud ice cloud S NF undefined due to known separability problems 3 2 IMPLEMENTATION OF CLOUD TYPE CT CT is extracted by PGE02 of the SAFNWC MSG software package Detailed information on how to run this software package is available in the software user manual AD 3 The software architecture of PGEO2 has been strongly modified in version v2010 to make the life easier for the user It is now very similar to the other PGEs When a new region is defined the us
39. lude the cloud top height assignment for aviation forecast activities The product may also serve as input to mesoscale models or to other SAF NWC product generation elements The CTTH product contains information on the cloud top temperature and height for all pixels identified as cloudy in the satellite scene 4 1 2 Outline of Cloud Top Temperature and Height CTTH algorithm The different steps of the processing applied to cloud classified image are listed below The exact process applied to each pixel depend on the availability of NWP and SEVIRI data If all mandatory NWP and SEVIRI data are available see list of input for CTTH The following process is then applied e RTTOV 9 radiative transfer model developed by NWP SAF is applied using NWP temperature and humidity vertical profile to simulate 6 2um 7 3um 13 4um 10 8um and 12 0um cloud free and overcast clouds successively on each vertical pressure levels radiances and brightness temperatures This process is performed in each segment of the image the size of the segment is defined by the user the default value being 16 16 SEVIRI IR pixels The vertical profiles used are temporally interpolated to the exact slot time using the two nearest in time NWP fields input by the user e The techniques used to retrieve the cloud top pressure depend on the cloud s type as available in CT product e For very low low or medium thick clouds The cloud top pressure is retrieve
40. must be at least be available every 210hPa e by defining the codes depending on local EMOS table of needed parameters When a new region is defined the user has now to manually prepare the CTTH model configuration files for this new region using a default CTTH model configuration file provided in the SAFNWC MSG software package There is an option for the user to monitor the so called CTTH preparation step before SEVIRI images are available to speed up the process By default this preparation step is performed during the CTTH execution step The CTTH execution step which includes the CTTH preparation step in case it has not been launched before is automatically launched by the Task Manager if real time environment is selected Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 T A A METEO TRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MFL SCI PUM 01_v3 2 v2 2 Page 29 32 4 2 1 Manual preparation of Cloud Top Temperature and Height CTTH model configuration file for each region When a new region is defined and added in system and run configuration files the user must manually prepares the CTTH model configuration files by adapting the default CTTH model configuration file available in the SAFNWC software package Besides the NWP parameters to be used the levels may be changed by the user only one param
41. nts Low Clouds in Sunglint is a specific module for low clouds identification in sunglint areas Local Spatial Texture Table 4 Test sequence over sea Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 eer ee RANE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEL SCI PUM 01_v3 2 v2 2 Page 11 32 2 1 3 Description of Cloud Mask CMa output The description of CMa output in HDF format is detailed in the output products format definition document AD 2 This section summarizes the CMa output fields a colour palette is also included in the HDF CMa output file for each field see 2 5 e The main product output consists in the following six categories coded on 3 bits 0 Non processed containing no data or corrupted data 1 cloud free no contamination by snow ice covered surface no contamination by clouds but contamination by thin dust volcanic clouds not checked 2 Cloud contaminated partly cloudy or semitransparent May also include dust clouds or volcanic plumes 3 Cloud filled opaque clouds completely filling the FOV May also include thick dust clouds or volcanic plumes 4 Snow Ice contaminated 5 Undefined has been processed but not classified due to known separability problems e 16 bits to describe which test was successful For each cloudy pixel the bits corresponding to the successful tests are activated
42. perature 1K Intercept Special count 150 K e 5 bits for effective cloudiness Linear conversion from count to effective cloudiness Cloudiness gain Countspits intercept corresponds to cloudiness ranging between Cloudiness and Cloudiness 5 Special count 5 lcount e 14 bits for quality 2 bits to define processing status 0 non processed encompasses CMa and or CT Non processed or undefined Image areas that may not be processed when the images size is not a multiple of the PGE03 segment size 1 non processed because FOV is cloud free 2 processed because cloudy but without result 3 processed because cloudy with result l bit setto 1 when RTTOV IR simulations are available 3 bits to describe NWP input data 0 undefined space 1 All NWP parameters available no thermal inversion 2 All NWP parameters available thermal inversion present 3 Some NWP pressure levels missing no thermal inversion 4 Some NWP pressure levels missing thermal inversion present 5 At least one mandatory NWP information is missing 2 0 1 bits to describe SEVIRI input data undefined space all SEVIRI useful channels available Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METEOTRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MFL SCI PUM 01_v3 2 v2 2 Page 28 32 2 at least one SEVIRI useful channel missin
43. r vapour content of the atmosphere by climatological values extracted from ancillary dataset but the quality of CMa is then lower e Ancillary data sets The following ancillary data remapped onto satellite images are mandatory o Land sea atlas Land sea coast atlas Elevation atlas Monthly minimum SST climatology Monthly mean 0 6m atmospheric corrected reflectance climatology land Monthly mean large band visible surface reflectance climatology land for HRV processing Monthly integrated atmospheric water vapour content climatology o Monthly climatology of mean air temperature at 1000 hPa Oo Or O O O These ancillary data are available in the SAFNWC software package on MSG full disk in the default satellite projection at full IR resolution They are extracted on the processed region by the CMa software itself Coefficients s file also called threshold tables containing satellite dependent values and look up tables for IR thresholds and for solar channels thresholds are available in the SAFNWC software package and are needed by the CMa software 2 3 2 Configurable parameters for Cloud Mask CMa Three configurables parameters are available in the default CMa model configuration file e CMA_SZSEG The size of the segment is configurable see its definition in 2 2 1 Its default value is 4 Information on how to change the size of the segment can be found in the software user manual AD 3 and in section 2 2 1 e T
44. region 20 3 2 2 The Cloud Type CT preparation step optional 21 3 23 The lowe Type CT execution Me ananas ananas 21 3 3 INPUTS AND CONFIGURABLE PARAMETERS FOR CLOUD TYPE CT 21 3 3 1 Eis o inputs jor Cloud Type CLlararrmememenammmmasetamantauenedn 21 3 3 2 Configurable parameters for Cloud Type OT ccsesacsseccsesscesscscscasccassscessecacesiessancoaaseads 22 3 4 CLOUD TYPE CT VALIDATION 5 2 2552c5sccscuasdadiedas inip Anieri Erare r ERE EON RA E ONAE Eni E rii i 23 3 4 1 Summary of Cloud Type CT validation restls esnrnsncnennnannnananna 23 3 4 2 Typical known problems and recommendation for use 23 35 EXAMPLE OF CLOUD TYPE CT VISUALISATION ccceesccccceesesssssseeeecccesesssssseeeeccceessesssseeees 23 4 CLOUD TOP TEMPERATURE AND HEIGHT CTTH PRODUCT cssseeee 25 4 1 DESCRIPTION OF CLOUD TOP TEMPERATURE AND HEIGHT CTTH PRODUCT s 00ss0000e00 25 4 1 1 Goal of Cloud Top Temperature and Height CTTH product 25 4 1 2 Outline of Cloud Top Temperature and Height CTTH algorithm 25 4 1 3 Description of Cloud Top Temperature and Height CTTH output 26 4 2 IMPLEMENTATION OF CLOUD TOP TEMPERATURE AND HEIGHT CTTH sssseeneeeeeseseeee00e 28 Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METEO FRANCE 53 4502 v2 2 amp CTTH PGE03 _ Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEFL SCI PUM 01_
45. rmation is mandatory It is computed by the CT software itself using the definition of the region and the satellite characteristics e NWP parameters The forecast fields of the following parameters remapped onto satellite images are used as input o surface temperatures o air temperature at 950hPa alternatively 925hPa to check low level inversion 850hPa 700hPa 500hPa and at tropopause level o total water vapour content of the atmosphere o altitude of the NWP model grid alternatively surface geopotential of the NWP model grid Required if NWP fields are used as input These remapped fields are elaborated by the SAFNWC software package from the NWP fields input by the user in GRIB format The NWP fields are not mandatory The CT software replaces missing NWP surface temperatures air temperature at 850hPa 700hPa 500hPa or total water vapour content of the atmosphere by climatological values extracted from ancillary dataset An alternative method is used in case of missing NWP air temperature at tropopause level The quality of CT is lower if some NWP fields are missing e Ancillary data sets The following ancillary data remapped onto satellite images are mandatory o Land sea atlas Elevation atlas Monthly minimum SST climatology Monthly mean 0 6um atmospheric corrected reflectance climatology land Monthly 0 6um and 1 6m white sky surface albedo climatology land Monthly integrated atmospheric water vapour content clim
46. rocessing itself 0 Non processed containing no data or corrupted data 1 Good quality high confidence 2 Poor quality low confidence 3 Reclassified after spatial smoothing very low confidence 1 bit for temporal processing indicator significant for cloud free pixels 0 Not performed 1 Performed 1 bit for HRV processing indicator significant for cloud free pixels 0 Not performed 1 Performed e 2 bits for dust detection Non processed containing no data or corrupted data dust non dust undefined due to known separability problems S D 2 bits for volcanic plume detection Non processed containing no data or corrupted data volcanic plume non volcanic plume undefined due to known separability problems S D mm 2 2 IMPLEMENTATION OF CLOUD MASK CMA CMa is extracted by PGEOI of the SAFNWC MSG software package Detailed information on how to run this software package is available in the software user manual AD 3 The software architecture of PGEO1 has been strongly modified in version v2010 to make the life easier for the user It is now very similar to the other PGEs When a new region is defined the user has now to manually prepare the CMa model configuration files for this new region using a default CMa model configuration file provided in the SAFNWC MSG software package There is an option for the user to monitor the so called CMa preparation step before SEVIRI images are available to speed
47. ssential for the generation of the cloud top temperature and height product and for the identification of precipitation clouds Finally it is also essential for the computation of radiative fluxes over sea or land which are SAF Ocean amp Sea Ice products The CT product therefore contains information on the major cloud classes fractional clouds semitransparent clouds high medium and low clouds including fog for all the pixels identified as cloudy in a scene A second priority is the distinction between convective and stratiform clouds implementation not planned before 2012 and the identification of clouds for which the top mainly consists of water droplets 3 1 2 Outline of Cloud Type CT algorithm The CT algorithm is a threshold algorithm applied at the pixel scale based on the use of CMa and spectral amp textural features computed from the multispectral satellite images and compared with a set of thresholds The set of thresholds to be applied depends mainly on the illumination conditions whereas the values of the thresholds themselves may depend on the illumination the viewing geometry the geographical location and NWP data describing the water vapour content and a coarse vertical structure of the atmosphere Opaque clouds are first separated from semi transparent and from fractional sub pixel clouds using brightness temperature differences T10 8um T12 0um T8 7um T10 8um or T3 9um T10 8um and RO 6um at daytime Opaq
48. ssing of the SEVIRI images itself over the region This process consists in the launch of the command PGEO02 by the Task manager The CT is then performed using the thresholds and simulations prepared during the preparation step 3 3 INPUTS AND CONFIGURABLE PARAMETERS FOR CLOUD TYPE CT 3 3 1 List of inputs for Cloud Type CT The input data to the CT algorithm are described in this section Mandatory inputs are flagged whereas the impact of missing non mandatory data on the processing are indicated e Satellite imagery The following SEVIRI bi directional reflectances or brightness temperatures are needed at full IR spatial resolution Tiosum 712 0 The CT software checks the availability of SEVIRI channels for each pixel no results are available for pixels where at least one mandatory channel is missing If T8 7um or R1 6um are missing the cloud phase flag is not computed Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 METEOTRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEL SCI PUM 01_v3 2 v2 2 Page 22 32 The SEVIRI channels are input by the user in HRIT format and extracted on the processed region by SAFNWC software package e CMa cloud categories The CMa cloud categories are mandatory They are computed by the CMa software e Sun and satellite angles associated to SEVIRI imagery This info
49. the atlas values and the thresholds will be derived over all the processed regions at the horizontal resolution of the segment Note also that the land sea atlas will be available at the full IR resolution allowing the identification of the surface type land or sea of all IR pixels whatever the segment size The quality is not very much dependent on the segment size if lower than 4 A segment size of 4 allows the preparation step to be 9 times faster than if a segment size of 1 was used e PHASE_COMPUTATION default value TRUE a flag defining if the cloud phase flag should be computed PHASE_COMPUTATION flag is checked at the execution step It should be assigned to TRUE or FALSE PGE02 computes the cloud phase flag if its value is TRUE This flag has been made configurable to allow users being blocked by hardware resources to still run the PGEO2 by assigning it to FALSE in the configuration file Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MEL SCI PUM 01 T A METFOTRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEFL SCI PUM 01_v3 2 v2 2 Page 21 32 e CT_PHASE_SZSEG default value 8 the size of the segment for the cloud phase flag computation This default value may be manually changed independently from CMA_SZSEG or CT_SZSEG or the size available in the lines NWP_PARAMxx Segments are square boxes in the satellite proj
50. therefore useless the infrared channels at 10 8um and 12 0um are contaminated by the surface and cannot therefore be used as for opaque clouds e A gap filling procedure is applied in semi transparent cloud top pressure field in boxes of fixed size 32x32 SEVIRI IR pixels a cloud top pressure is computed as the average pressure of all pixels containing semi transparent clouds inside the current and the eight surrounding boxes This average cloud top pressure is then assigned to all pixels of the current box containing semi transparent clouds and having no retrieved cloud top pressure e Cloud top temperature and height above sea level are then computed from their pressure using general modules During these processes the atmospheric vertical profiles are temporally interpolated to the exact slot time using the two nearest in time NWP outputs fields e Effective cloudiness defined as the fraction of the field of view covered by cloud the cloud amount multiplied by the cloud emissivity in the 10 8um window channel is also computed during the processing It is equal to 1 0 for thick clouds and takes a value between 0 and 1 for semi transparent clouds In case some mandatory NWP or SEVIRI data are missing see list of inputs for CTTH Cloud top temperature of very low low medium and high clouds are then computed by applying a climatological atmospheric absorption correction to the 10 8um brightness temperature using look up tables Th
51. tt ts titt t kiri ententes 9 2 11 CO Cloud Mask CM DOM 9 2 1 2 Outline of Cloud Mask CMa algorithm ss 9 21 3 Detroit ll 2 2 IMPLEMENTATION OF CLOUD MASK CMA sssssssssssessssssssesssssesssssssessssssssessseeeeseeees 12 Manual preparation of Cloud Mask CMa model configuration file for each region 13 2 2 2 The Cloud Mask CMa preparation step optional 13 2 2 3 The Cloud Mask CMa XeCunon Step erinran aa E RR 13 23 INPUTS AND CONFIGURABLE PARAMETERS FOR CLOUD MASK CMA ccsssscccceeeeeeeessneeeees 14 2 3 1 List of inputs Jor Cloud Mask CMG cs brsusisssisstaaexecegsyesanvtaxstasvanwnsaqsiaequnesanesenenenesiaoee 14 20 2 Configurable parameters for Cloud Mask CMa ss 15 2 4 CLOUD MASK CMA VALIDATION tite aa in tn ni ini 15 2 4 1 Summary of Cloud Mask CMa validation results T3 2 4 2 Typical known problems and recommendation for use 16 2 5 EXAMPLE OF CLOUD MASK CMA VISUALISATION cccccccccessssssseeeeeeeeesesssaeeeeeeeeeesessnaeeees 16 3 CLOUD TYPE CCE PRODUC aAA A AARAA ERAAN ARARNAR RARER NEARER RARA RAAE 18 3 1 DESCRIPTION OF CLOUD TYPE CT PRODUCT iii eines 18 3 1 1 Goal of Cloud Type CT BFC riens rennes 18 3 1 2 Outline of Cloud Typa CT al ortdihnt ss sahitnnanasatutadanananaes 18 SU ES DPDeseniphon o Cloud Lype CT VON Ppul sranani n neea ENTE 18 3 2 IMPLEMENTATION OF CLOUD TYPE C ER nan 20 3 21 Manual preparation of Cloud Type CT model configuration file for each
52. ue clouds are then separated in very low low mid level high or very high clouds using their T10 8mm brightness temperatures which are compared to NWP forecast air temperatures at various pressure levels Details are available in the algorithm theoretical basis document for cloud products AD 4 A separate processing is applied to compute the cloud phase flag based on the use of CT cloud type T8 7um T10 8um all illumination RO 6um and R1 6um at daytime 3 1 3 Description of Cloud Type CT output The description of CT output in HDF format is detailed in the output products format definition document AD 2 This section summarizes the CT output fields a colour palette is also included in the HDF CT output file for each field see 3 5 e The main product output consists in the following twenty one categories coded on 5 bits 0 non processed containing no data or corrupted data 1 cloud free land no contamination by snow ice covered surface Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MEL SCI PUM 01 METEOTRANCE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MFL SCI PUM 01_v3 2 v2 2 Page 19 32 ONDARRA g 10 11 12 13 14 15 16 17 18 19 20 no contamination by clouds but contamination by thin dust volcanic clouds not checked cloud free sea no contamination by snow ice covered surface no contamination by
53. v3 2 v2 2 Page 5 32 4 2 1 Manual preparation of Cloud Top Temperature and Height CTTH model configuration file FOP each TERIOM sis casccssciccsesdcsascacetedsistansdasdsnsatasidonedansderedsastdesedesuiemededebennsedescd 29 4 2 2 The Cloud Top Temperature and Height CTTH preparation step optional 29 4 2 3 The Cloud Top Temperature and Height CTTH execution step 24 4 3 INPUTS AND CONFIGURABLE PARAMETERS FOR CLOUD TOP TEMPERATURE AND HEIGHT a nd a E 29 4 3 1 List of inputs for Cloud Top Temperature and Height CTTH scccssceeseeesseeeees 29 4 3 2 Configurable parameters for Cloud Top Temperature and Height CTTH 31 4 4 CLOUD TOP TEMPERATURE AND HEIGHT CTTH VALIDATION ses 31 4 4 1 Summary of Cloud Top Temperature and Height CTTH validation results 31 4 4 2 Typical known problems and recommendation for use 31 4 5 EXAMPLE OF CLOUD TOP TEMPERATURE AND HEIGHT CTTH VISUALISATION 32 Product User Manual for Cloud Products CMa PGEO01 v3 2 CT Code SAF NWC CDOP MFL SCI PUM 01 eT ee RANE PGE02 v2 2 amp CTTH PGE03 Issue 3 2 Date 15 February 2012 NWC SAF File SAF NWC CDOP MEL SCI PUM 01_v3 2 v2 2 Page 6 32 List of Tables and Figures Table 1 Listot Applicable DOC MERE sscice cvcacesaecvascian cans airevanroauaacaocianci esa e EER ETER ERRE Sat 8 Table 2 Listof Referenced DOG Hesse annuel 8 Table IS CODEN Dur Rs nement 10 T

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Product User Manual for “Cloud Products”