OVERVIEW THIS PROPOSAL ESTIMATES SNOW EMISSIVITY OVER THE US BY ASSIMILATING REMOTELY SENSED MULTI-FREQUENCY PASSIVE MICROWAVE LAND SURFACE TEMPERATURE (LST) AND ALBEDO DATA INTO AN ENSEMBLE BATCH SMOOTHER (ENBS) DATA ASSIMILATION FRAMEWORK. PRIOR STUDIES HAVE SHOWN THAT MODELS AND REMOTE SENSING DATA CANNOT ACCURATELY ESTIMATE SNOW EMISSIVITY DUE TO LIMITATIONS ATTRIBUTED TO EACH OF THEM. HENCE IN THIS PROJECT WE WILL MERGE LAND SURFACE (CROCUS) AND SNOW EMISSION MODELS (MEMLS) WITH MULTI-FREQUENCY PASSIVE MICROWAVE OBSERVATIONS LST AND ALBEDO WITHIN AN ENBS SCHEME TO GENERATE AN ACCURATE SNOW EMISSIVITY PRODUCT. WE HYPOTHESIZE THAT IMPLEMENTATION OF AN ENSEMBLE-BASED DATA ASSIMILATION ALGORITHM TO INTEGRATE MULTI-FREQUENCY PASSIVE MICROWAVE LST AND ALBEDO MEASUREMENTS WITH THE SNOWPACK-MICROWAVE EMISSION MODEL SIGNIFICANTLY IMPROVES SNOW EMISSIVITY ESTIMATES FROM MODELING TOOLS. RELEVANCE OUR PROPOSAL IS HIGHLY RELEVANT TO THIS SOLICITATION BECAUSE IT ADDRESSES THREE OF ITS OBJECTIVES: (1) USING DATA FROM NASA-SPONSORED LARGER-SCALED SNOW CAMPAIGNS (2) MULTIVARIATE DATA ASSIMILATION AND (3) INCORPORATING NEW MODELS AND DATA ASSIMILATION SYSTEMS INTO THE LAND INFORMATION SYSTEM (LIS) AND USING LIS AS A DEVELOPMENT AND MODELING TESTBED. APPROACH IN THIS PROPOSAL REMOTELY SENSED MULTI-FREQUENCY PASSIVE MICROWAVE LST AND ALBEDO MEASUREMENTS WILL BE COMBINED WITH THE RELEVANT MODELS WITHIN A DATA ASSIMILATION SYSTEM TO DEVELOP SPATIALLY AND TEMPORALLY CONTINUOUS ESTIMATES OF SNOW EMISSIVITY OVER THE US. FOR THIS PURPOSE THE LIS WILL BE AUGMENTED BY THE CROCUS SNOW MODEL THE MEMLS MICROWAVE EMISSION MODEL AND THE ENSEMBLE BATCH SMOOTHER (ENBS) DATA ASSIMILATION ALGORITHM. THE LIS PROVIDES SEVERAL FORCING DATASETS SUCH AS MERRA2 NLDAS AND ECMWF; PASSIVE MICROWAVE BRIGHTNESS TEMPERATURE FROM AMSR-E AMSR2; AND LST AND ALBEDO FROM MODIS. WE TAKE ADVANTAGE OF THE LIS FORCING DATA TO RUN THE SNOW MODEL AND THE ABOVE MENTIONED REMOTE SENSING DATA TO PERFORM THE DATA ASSIMILATION SCHEME. FINALLY SNOW PIT DATA GROUND BASED PASSIVE MICROWAVE RADIOMETER AIRBORNE PASSIVE MICROWAVE DATA AND IN-SITU MEASUREMENTS FROM THE CLPX AND SNOWEX CAMPAIGNS WILL BE USED TO EVALUATE THE SNOW EMISSIVITY ESTIMATES.