THIS PROPOSAL DIRECTLY ADDRESSES THE EMERGING NEED TO UNDERSTAND AND QUANTIFY THE NATURE OF LAND-ATMOSPHERE INTERACTIONS AS THEY EXIST TODAY, AS THEY MAY BE MODULATED BY THE RADIATIVELY-DRIVEN COMPONENT OF CLIMATE CHANGE, AND AS THEY MAY EVOLVE WITH CHANGING LAND USE. THE PROPOSED WORK WILL BUILD UPON RECENT ADVANCES IN PROCESS-BASED UNDERSTANDING OF COUPLING BY GOING BEYOND THE REGIONS, METRICS AND TIME PERIODS THAT HAVE RECENTLY BEGUN TO BE STUDIED, AND BY MORE THOROUGHLY EXPLORING HOW ANTHROPOGENIC LAND USE CAN MODIFY THE PHYSICAL AND BIOSPHERIC PATHWAYS THROUGH WHICH LAND-ATMOSPHERE INTERACTIONS ARE INITIATED AND MAINTAINED.THIS PROPOSAL DOES NOT ATTEMPT TO IMPROVE PREDICTIONS OF DECADAL CLIMATE VARIABILITY, BUT RATHER INVESTIGATES HOW SUB-SEASONAL TO SEASONAL VARIABILITY AND PREDICTABILITY, WHERE LAND-ATMOSPHERE FEEDBACKS HAVE BEEN FOUND TO BE CRUCIAL, EVOLVE ACROSS DECADAL TIME SCALES AS A FUNCTION OF KNOWN, EXPECTED AND POSSIBLE ANTHROPOGENIC CHANGES. THIS PROPOSAL UNDERTAKES THE CALL TO ADDRESS HUMAN PROCESSES THAT DRIVE THE CLIMATE SYSTEM, INCLUDING THEIR PERTINENCE TO AGRICULTURE, FORESTRY AND LAND COVER/USE. THE PROPOSED WORK WILL DIRECTLY IDENTIFY AND QUANTIFY FEEDBACK LOOPS BETWEEN LAND AND ATMOSPHERE, AND THEIR IMPACTS ON NATURAL AND HUMAN SYSTEMS. SPECIFICALLY, TRENDS AND UNCERTAINTIES IN LAND USE CHANGE, IRRIGATION EXPANSION, AND OTHER AGRICULTURAL PRACTICES WILL BE INVESTIGATED IN TERMS OF THEIR EFFECTS ON THESE FEEDBACKS IN A CHANGING CLIMATE. A RANGE OF OBSERVATIONAL DATA WILL BE EMPLOYED TO VALIDATE FUNCTIONAL RELATIONSHIPS AMONG STATES AND FLUXES IN CESM FOR CURRENT CLIMATE, INFORMING MODEL VALIDATION AND DEVELOPMENT.