TROPICAL AQUATIC SYSTEMS INCLUDING FLOODPLAINS AND OTHER WETLANDS LAKES AND RIVERS ARE MAJOR SOURCES OF METHANE TO THE ATMOSPHERE.THE CONSIDERABLE UNCERTAINTY ABOUT THE ESTIMATED FLUXES OF METHANE STEMS FROM THE LARGE SEASONAL AND INTER-ANNUAL VARIATIONS IN ECOLOGICAL CONDITIONS AND INUNDATION TYPICAL OF FLOODPLAINS AND OTHER WETLANDS. IN THIS PROPOSED PROJECT WE WILL COMBINE RESULTS FROM OUR FIELD MEASUREMENTS HYDROLOGICAL SIMULATIONS AND ADVANCES IN REMOTE SENSING TO DEVELOP MECHANISTIC MODELS THAT COUPLE FLOODPLAIN INUNDATION DYNAMICS TO THE PRODUCTION AND EMISSION OF METHANE. OUR WORK WILL QUANTIFY AND REDUCE UNCERTAINTY ASSOCIATED WITH ESTIMATES OF METHANE FLUXES AND EXPAND UNDERSTANDING OF THEIR TEMPORAL AND SPATIAL VARIABILITY. OUR RESULTS WILL PROVIDE NECESSARY INPUTS TO REGIONAL ATMOSPHERIC MODELS OF METHANE FLUXES DERIVED FROM AIRBORNE CAMPAIGNS AND SATELLITE RETRIEVALS AND PROVIDE KEY IMPROVEMENTS IN THE TROPICS FOR MODELS APPLIED GLOBALLY. AMONG TROPICAL RIVER SYSTEMS THE AMAZON BASIN IS THE LARGEST AND HAS THE MOST EXTENSIVE FLOODPLAINS. HENCE OUR ANALYSES WILL FOCUS ON AQUATIC SYSTEMS IN THE AMAZON BASIN AND BE EXTENDED TO TROPICAL SYSTEMS ELSEWHERE BASED ON MODELING AND REMOTE SENSING. REMOTE SENSING OF INUNDATION AND VEGETATIVE DYNAMICS WILL BE COMBINED WITH RECENT RESULTS FROM IN SITU MEASUREMENTS OF METHANE FLUXES RELATED PHYSICAL PROCESSES AND HYDROLOGICAL MODELS TO PROVIDE REGIONAL ESTIMATES OF METHANE FLUXES. WE WILL UTILIZE EXISTING DATASETS COMPLEMENTED BY FOCUSED FIELD STUDIES TO DEVELOP AND VALIDATE A MODEL OF METHANE EVASION TAILORED TO TROPICAL AQUATIC SYSTEMS WITH STRONG SEASONAL AND INTER-ANNUAL VARIATIONS IN INUNDATION WATER DEPTHS AND VEGETATIVE COVER.OUR PROPOSAL TO NASA'S INTERDISCIPLINARY RESEARCH IN EARTH SCIENCE PROGRAM (SUBELEMENT 1: UNDERSTANDING THE GLOBAL SOURCES AND SINKS OF METHANE) ADVANCES UNDERSTANDING OF THE SOURCES OF METHANE BY COMBINING REMOTE SENSING ANALYSES WITH MECHANISTIC UNDERSTANDING OF THE PHYSICAL CHEMICAL AND BIOLOGICAL PROCESSES INVOLVED IN AN INTEGRATED INTERDISCIPLINARY PROJECT. RESULTS OF OUR INVESTIGATIONS WILL IMPROVE SUBSTANTIALLY CAPABILITIES FOR PREDICTIONS AND SIMULATIONS OF METHANE EMISSIONS AND IMPORTANTLY THEIR TEMPORAL AND SPATIAL VARIATIONS WITHIN TROPICAL AQUATIC SYSTEMS. WE COMBINE EXPERTISE IN BIOGEOCHEMISTRY ECOLOGY LIMNOLOGY HYDROLOGY HYDRODYNAMICS REMOTE SENSING AND MODELING TO EXAMINE AN INTEGRATED SET OF PROCESSES THAT SUPPLY METHANE TO THE TROPOSPHERE.