GLOBAL ECOSYSTEM FUNCTION IS HIGHLY DEPENDENT ON CLIMATE AND ATMOSPHERIC COMPOSITION YET ECOSYSTEM RESPONSES TO ENVIRONMENTAL CHANGES REMAIN UNCERTAIN. WATER IN PARTICULAR PROVIDES A STRONG CONSTRAINT ON THE AMOUNT OF VEGETATION THAT CAN BE MAINTAINED IN AN ECOSYSTEM AND ITS PRODUCTIVITY. INDEED WATER AVAILABILITY LIMITS PLANT GROWTH AND PRODUCTIVITY IN ALMOST ALL TERRESTRIAL ECOSYSTEMS. BOTH THE AMOUNT OF WATER IN THE FORM OF SOIL MOISTURE AND ITS STATE ARE IMPORTANT. FOR EXAMPLE ECOSYSTEMS IN SEMI-ARID REGIONS ARE HIGHLY DEPENDENT ON THE AMOUNT OF MOISTURE IN THE SOIL WHILE ECOSYSTEMS IN COLD REGIONS ARE DEPENDENT ON THE FREEZE-THAW STATE. SMAP REPRESENTS AN UNPARALLELED OPPORTUNITY TO UNDERSTAND ECOSYSTEM RESPONSES TO WATER AVAILABILITY IN PARTICULAR THROUGH FUSING SMAP OBSERVATIONS WITH MODIS/VIIRS OBSERVATIONS AND GLOBAL EARTH SYSTEM MODELS. WE PROPOSE TO LEVERAGE THAT OPPORTUNITY USING GLOBAL SMAP L3 PRODUCTS OF SOIL MOISTURE AND FREEZE-THAW STATE TOGETHER WITH THE L4 NET ECOSYSTEM EXCHANGE PRODUCT IN COMBINATION WITH MODIS VIIRS AND OTHER MISSIONS TO CHARACTERIZE THE EXTENT AND DYNAMICS OF WATER LIMITATION OF GLOBAL TERRESTRIAL ECOSYSTEMS. PREVIOUS EFFORTS BY THIS TEAM HAVE DEVELOPED VEGETATION FUNCTIONAL RESPONSES FROM MODIS AND GIMMS AND USED THEM TO QUANTIFY THE RESPONSE OF VEGETATION COVER TO SPATIAL AND TEMPORAL CHANGES IN CLIMATE AND PRECIPITATION. THIS PROJECT WILL COMBINE THE STRENGTH OF THIS ANALYSIS WITH SMAP ALLOWING US TO ASSESS THE CONTROL GLOBAL WATER AVAILABILITY EXERTS OVER VEGETATION COVER ECOSYSTEM PRODUCTIVITY AND THE GLOBAL CARBON CYCLE. PARTICULARLY BENCHMARKS WILL BE DEVELOPED FOR EARTH SYSTEM MODELS FOCUSED ON SPATIAL RESPONSES OF VEGETATION STATE AND FUNCTION TO CHANGES IN SOIL MOISTURE IN THE WORLDS DRY REGIONS AND SPATIAL RESPONSES TO CHANGES IN FREEZE-THAW STATE IN THE WORLDS COLD REGIONS. THESE BENCHMARKS WILL BE IMPLEMENTED INTO THE INTEGRATED LAND MODEL BENCHMARK (ILAMB) A MODEL-DATA INTERCOMPARISON AND INTEGRATION PLATFORM IN WHICH THIS TEAM IS HEAVILY INVOLVED. ILAMB IS DESIGNED TO IMPROVE THE PERFORMANCE OF LAND MODELS AND IN PARALLEL IMPROVE THE DESIGN OF NEW MEASUREMENT CAMPAIGNS TO REDUCE UNCERTAINTIES ASSOCIATED WITH LAND SURFACE PROCESSES.