Apresenta

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Land Surface Analysis SAF Contributions to
NWP Isabel F. Trigo
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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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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
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LSA SAF PRODUCTS
Priority 1 2 Benefits for NWP
Snow Cover Validation Albedo of Snow Areas Initialisation of snow mass in DA
Albedo Broadband/Spectral albedo updates
Land Surface Temperature Validation DA
? Sfc Short-wave Fluxes ? Sfc Long-wave Fluxes Validation forcing for global soil moisture AN.
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LSA SAF PRODUCTS
Priority 3 4 Benefits for NWP
Soil Moisture Evapotranspiration Validation
Vegetation Cover LAI Possible use for monthly/seasonal updates
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Snow Cover
Coverage Europe (Global) Resolution 5x5 km
(1x1km) 15min for MSG daily maps Delivery
Time - Near Real Time
white - class snow light grey -class
partially snow covered green class class
clear land
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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
Broadband Albedo
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Land Surface Temperature
Coverage MSG disk (Global) Resolution 3x3
km 15 min Delivery Time - Near Real
Time Accuracy 1 2 K
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II LSA SAF / ECMWF Collaboration (Pedro Viterbo
and Anton Beljaars)
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Underestimation of Tb daily cycle over
arid/semi-arid regions
Overestimation Tb diurnal cycle, mostly along the
ITCZ
Tb_obs ? Tb_ECMWF averaged for 1-15 Feb 2001
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• 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.
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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
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ECMWF Land Surface Model - TESSEL
Dry Vegetated Surfaces
Bare Ground Tile
Ra does not take into account the wind shielding
effect of surrounding vegetation.
Hbare_g is overestimated, particularly over
sparsely vegetated areas.
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Revised TESSEL
Rs Resistance to turbulent heat transfer within
the under canopy layer. - sparseness of the
vegetation - canopy height - ...
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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 2002.
Tb Daily Amplitude
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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
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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.
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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.