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

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

LSA SAF PRODUCTS Priority 1 & 2Benefits for NWP Snow CoverValidation; Albedo of Snow Areas; Initialisation of snow mass in DA AlbedoBroadband/Spectral albedo updates Land Surface TemperatureValidation; DA  Sfc Short-wave Fluxes  Sfc Long-wave Fluxes Validation; forcing for global soil moisture AN.

LSA SAF PRODUCTS Priority 3 & 4Benefits for NWP Soil Moisture Evapotranspiration Validation Vegetation Cover LAI Possible use for monthly/seasonal updates Development Pre-operational Operational

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

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 nm; nm; nm Accuracy - ~1% Broadband Albedo Development Operational Beta-Users

Land Surface Temperature Coverage – MSG disk; (Global) Resolution – 3x3 km; 15 min Delivery Time - Near Real Time Accuracy – ~1 – 2 K Development Operational Beta-Users

II – LSA SAF / ECMWF Collaboration (Pedro Viterbo and Anton Beljaars) Assimilation of LST ? Window Channel Brightness Temperatures (10.50 –  m) METEOSAT – 7 clear sky Tb_OBS ECMWF model equivalent Tb_ECMWF To assess the quality of modelled land surface temperature. To monitor the quality of the observations by identifying gross errors / systematic problems in the data.

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

Sources of Window channel Tb Systematic Errors: (i)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,

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

ECMWF Land Surface Model - TESSEL RaRa,nv Tc T skin Dry Vegetated Surfaces Bare Ground Tile: Ra does not take into account the wind shielding effect of surrounding vegetation. H bare_g is overestimated, particularly over sparsely vegetated areas.

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

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

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

II – LSA SAF / ECMWF Collaboration The comparison of Meteosat-7 window channel Tb (clear sky) with Tb_ECMWF shows that the modelled Tskin diurnal cycle 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.

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.