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Land Surface Analysis SAF: Contributions to NWP Isabel F. Trigo

Land Surface Analysis SAF: Contributions to NWP Isabel F. Trigo. Scope of Presentation. I – LSA SAF - Products relevant for NWP - Schedule - Beta – Users II – LSA SAF / ECMWF joint Collaboration - Assimilation of LST ? - ECMWF Land Surface Scheme - Future Work.

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Land Surface Analysis SAF: Contributions to NWP Isabel F. Trigo

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  1. Land Surface Analysis SAF: Contributions to NWP Isabel F. Trigo

  2. Scope of Presentation I – LSA SAF - Products relevant for NWP - Schedule - Beta – Users II – LSA SAF / ECMWF joint Collaboration - Assimilation of LST ? - ECMWF Land Surface Scheme - Future Work

  3. I – Land Surface Analysis SAF Satellite Application Facilities Development & Processing Centres within the EUMETSAT Applications Ground Segment:  Meteorological products  Software Packages Using MSG and EPS data. LSA SAF Consortium of 13 organisations / 8 member states Host Institute: IM

  4. LSA SAF PRODUCTS

  5. 2003 2004 2005 2006 2007 2008 Operational Pre-operational Development LSA SAF PRODUCTS

  6. 2003 2004 2005 2006 2007 2008 Beta-Users Operational Development Snow Cover Coverage–Europe; (Global) Resolution–5x5 km; (1x1km) 15min for MSG; daily maps DeliveryTime-Near Real Time white - class “snow”; light grey -class “partially snow covered”; green class – class “clear land”;

  7. 0.30 0.15 0 2003 2004 2005 2006 2007 2008 Beta-Users Operational Development Albedo Broadband Albedo Coverage–MSG disk; (Global) Resolution–3x3 km; 10 days Delivery Time-Near Real Time Content–Spectral & Broadband: VIS 0.6; VIS 0.8; IR 1.6 300-4000 nm; 400-700nm; 700-4000nm Accuracy-~1%

  8. 2003 2004 2005 2006 2007 2008 Beta-Users Operational Development Land Surface Temperature Coverage–MSG disk; (Global) Resolution–3x3 km; 15 min Delivery Time-Near Real Time Accuracy–~1 – 2 K

  9. Assimilation of LST ? Window Channel Brightness Temperatures (10.50 – 12.50 m) METEOSAT – 7 clear sky .......... Tb_OBS ECMWF modelequivalent .......... Tb_ECMWF To monitor the quality of the observations byidentifying gross errors / systematic problems in the data. To assess the quality of modelled landsurfacetemperature. II – LSA SAF / ECMWF Collaboration (Pedro Viterbo and Anton Beljaars)

  10. Underestimation of Tb daily cycle over arid/semi-arid regions OverestimationTb diurnal cycle, mostly along the ITCZ Tb_obsTb_ECMWF averaged for 1-15 Feb 2001

  11. Sources of Window channel Tb Systematic Errors: • cloud screening of the observations... •  • - threshold for the %Clear Sky pixels; • - MSG will allow more accurate cloud masks. • (ii) underestimation of modelled diurnal amplitudes of Tb_ECMWF in clear sky conditions  underestimation of LST diurnal cycle (particularly over arid and semi-arid regions) Further Details: Trigo and Viterbo (2003), J. Appl. Met., 42, 1463-1479.

  12. A pre-requisite to contemplate assimilation: The model has to look like the observations Window Channel Tb bias (and thus LST bias) ~ 10K in semi-arid regions strongly limits the assimilation of:  Window channel TOA Radiances / LST product;  TOVS channels sensitive to the lower troposphere, over land. A set of sensitivity experiments of Tb amplitude to surface parameters / variables pointed  Model deficiencies in the LAND – ATMOSPHERE Aerodynamic Coupling

  13. Ra,nv Ra Tc Tskin ECMWF Land Surface Model - TESSEL Dry Vegetated Surfaces Bare Ground Tile: Radoes not take into account thewind shielding effect of surrounding vegetation. Hbare_gis overestimated, particularly over sparsely vegetated areas.

  14. Ra,nv Ra Tc Rs Tskin Revised TESSEL Rs – Resistance to turbulent heat transfer within the under canopy layer. - sparseness of the vegetation; - canopy height; - ...

  15. ECMWF 1-Column Model Western Sahara – Validation Period Parameters inRs 1) Estimated by fitting daily Tb_ECMWF amplitudes to Tb_OBS; 1-15 Feb 2001; 2) Fixed for each grid point 1-15 Feb 2002. Tb Daily Amplitude

  16. Summary I – LSA SAF • Priority 1 Products: Snow Cover, Albedo, and Land Surface Temperature • Priority 2 Products: Downwelling Surface Short & Long wave Fluxes • Priority  3 - Vegetation Parameters: FVC, LAI - Soil Moisture / Evapotranspiration • Beta-Users - Please contact LSA SAF NOW ! - Pre-Operational in 2005 • Operational Phase - 2007

  17. II – LSA SAF / ECMWF Collaboration •The comparison of Meteosat-7 window channel Tb (clear sky) with Tb_ECMWF shows that the modelled Tskin diurnalcycle is underestimated over arid / semi-arid regions.  Limits assimilation of LST & Channels that peak in the lower troposphere. •Sensitivity experiments pointed to deficiencies in the Land Surface – Atmospheric aerodynamic coupling.  TESSEL Bare Ground Tiles ignore wind shielding effect of the surrounding vegetation. •Introducing an extra resistance Rs to turbulent heat transfer within the canopy layer substantially reduces the ECMWF cold bias of Tb daily amplitudes.

  18. Next •Estimate Rs parameters for Meteosat (MSG) disk (by fitting daily amplitudes of Tb_ECMWF to the observations). •Study the impact of the improved land Tskin in the assimilation of TOVS channels sensitive to the lower troposphere. •Test 1D-var assimilation of window channels TOA radiances/ retrieved LST to further improve the model Tskin over land.

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