Surface

Land surface microwave emissivities have been calculated over the globe from SSM/I observations, using ancillary information from meteorological reanalysis and other satellite observations to remove the contributions of the atmosphere, clouds, and rain [Prigent et al., JGR, 102, 21867-21890, 1997; Prigent et al., RS, 33, 745-751, 1998]. Examples of monthly mean global microwave emissivity maps are available at http://isccp.giss.nasa.gov/products/browsesurf.html.

The synergy between microwave emissivities and other satellite observations (thermal IR, ERS scatterometer responses, AVHRR NDVI) have been examined for different applications [deserts, Prigent et al., JGR, 104, 12147-12158, 1999; vegetation, Prigent et al., JGR, 106, 20665-20685, 2001; wetlands, Prigent et al., GRL, 28 , 4631-4634, 2001].

The angular and frequency dependence of the land surface microwave emissivities were examined for potential extrapolation for AMSU applications [Prigent et al., IEEE TGRS, 38, 2373-2386, 2000]

A neural network inversion scheme, including first guess information, has been developed to retrieve simultaneously the surface skin temperature, the atmospheric water vapor, the cloud liquid water, and the surface emissivities over land from SSM/I and infrared radiance observations [Aires et al., JGR, 106, 14887-14907, 2001] using pre-calculated monthly-mean emissivities as first guess estimates.

We are now in the process of calculating 10 years of monthly mean land surface emissivites from SSM/I, in order to understand the inter-annual variability of these signatures, along with the analysis of other complementary satellite observations (ERS scatterometer, AVHRR NDVI).