Since 2004 we have worked on developing a dynamically updated, global database of microwave surface emissivities at each of the AMSR-E channel frequencies and polarizations by combining in a complementary and physically consistent manner observations from AMSR-E and MODIS instruments. The unprecedented collocation aboard the Aqua satellite of the AMSR-E microwave imager and the MODIS instrument (which provides surface temperature (LST) and cloud mask data) and good agreement found so far between MODIS LST�s and AMSR-E measurements have helped bring the quality of the emissivity product to the level needed for useful atmospheric and surface parameter retrieval over land in clear and cloudy conditions. Under the current proposal we will continue validation of the AMSR-E emissivities and will refine the database through improved quality control, Earth gridding strategy, and better water vapor correction. Since we have found that microwave surface penetration seems to be widespread (affecting, for example, most semi-arid and arid areas) we will also explore strategies for dealing with both emissivity derivation and atmospheric/surface parameter retrievals where penetration is a significant factor. The microwave database can be a powerful tool beyond retrieval applications - for example, for validating emissivity models used in satellite data assimilation, surface change monitoring, and climate applications. This work we will also provide an opportunity to explore correlations between infrared and microwave emissivities.
