1. Evaluation of modeled microwave land surface emissivities with satellite-based estimates
C. Prigent and F. Aires (Estellus + Observatoire de Paris )
P. Liang and J.-L. Moncet (AER)
T. Tian (NASA)
S. Boukabara (NOAA)

2. The use of modeled emissivity planed for the next generation of GPM algorithms.
On going model developments, with evaluation mostly at local scales, with CRTM.
In the current GPM algorithm, use of satellite-derived emissivity information (TELSEM classification).
Global evaluation of the CRTM modeled emissivity with the TELSEM emissivity
direct comparison of the emissivities
comparison of emissivities in the Tb space (use of the modeled and TELSEM emissivities in a radiative transfer code and comparison with AMSR-E Tbs)

3. I - Direct comparison of the emissivities
Modeled emissivity:
CRTM V2.0 with the Microwave Land Emissivity Model (MLEM), fed by the NASA Land Information System (LIS).
LIS-CRTM run at 0.25°x0.25°, at 30mn intervals, with output every 3h, from July 2004 to June 2009
Satellite-derived emissivity:
TELSEM, anchored to SSM/I-derived emissivity with the frequency, angular and polarization dependence estimated from AMSU/SSMI/TMI.

4. Emissivities for January
CRTM TELSEM
89GHz H 89GHz V 19GHz H 19GHz V

5. LIS/CRTM TELSEM
Dense forest Grassland
Deserts Snow and Ice

6. II - Comparisons in the Tb space with AMSR-E
LIS-CRTM and TELSEM used in a radiative transfer code and comparison with AMSR-E observations
MonoRTM and 1° 6-hourly NCEP GFS analysis
Four weeks in 2008 (one week in January, April, July, October)
Clouds filtered out

7. Tbs at 18.70 GHz for July (midnight)
V polarization H polarization
TELSEM LIS-CRTM AMSR-E

8. Correlations between the Tbs, for all frequencies and polarization

9. Tbs differences (Sim-AMSR) at 18 and 89 GHz (nighttime)
CRTM TELSEM
Snow Ice Desert Grassland Dense forest

10. Tbs differences (Sim-AMSR) at 18 and 89 GHz
CRTM TELSEM
CRTM TELSEM
Desert Grassland
Mid-night Mid-day

11. Conclusions
Rather good agreement between the modeled (CRTM) and satellite-derived emissivity estimates for vegetated areas
Over deserts and snow, significant differences, partly due to the model inputs
The ECMWF land surface emissivity model has also been tested. The results are much worse.
The comparison in the Tb space shows a better agreement with the satellite-derived emissivities.
Ideas to improve the emissivity modeling, especially over desert regions.
Joint work between modelers and remote sensing experts to be continued