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Evaluation of modeled microwave land surface emissivities with satellite-based estimates

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).

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Evaluation of modeled microwave land surface emissivities with satellite-based estimates

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  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. CRTM TELSEM Emissivities for January 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-CRTMAMSR-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

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