THE OVERARCHING OBJECTIVE OF THIS PROJECT IS THE DEVELOPMENT OF ENHANCEMENTS TO THE RRTMGP RADIATION CODE TO SUPPORT KEY GMAO AND GEOS-5 PRIORITIES. RRTMGP WHICH IS BEING DEVELOPED UNDER CURRENT SUPPORT FROM THE NASA MAP PROGRAM IS A HIGH- PERFORMANCE RADIATION CODE DESIGNED FOR THE CURRENT GENERATION OF COMPUTATIONAL ARCHITECTURES. THE CODE IS A COMPLETELY RESTRUCTURED AND MODERN VERSION OF THE RRTMG RADIATION CODE USED IN MANY GCMS. RRTMGP PRESERVES THE STRENGTHS OF THE EXISTING RRTMG PARAMETERIZATION ESPECIALLY THE HIGH ACCURACY OF THE K-DISTRIBUTION TREATMENT OF ABSORPTION BY GASES BUT THE ENTIRE CODE HAS BEEN REWRITTEN TO PROVIDE HIGHLY EFFICIENT COMPUTATION ACROSS A RANGE OF ARCHITECTURES. RRTMGP IS PLANNED TO BE THE NEXT RADIATION CODE IN GEOS-5 AND ITS INITIAL VERSION WILL BE ACCURATE FOR THE TYPICAL GCM CONFIGURATIONS OF SPATIAL AND TEMPORAL RESOLUTION VERTICAL RANGE GAS ABUNDANCES ETC. THE ENHANCEMENTS TO RRTMGP PROPOSED HERE WILL EXTEND THE RANGE OF VALIDITY OF GEOS-5 TO SUPPORT IMPORTANT SCIENTIFIC GOALS OF GMAO AND NASA-GSFC RESEARCHERS. IN PARTICULAR WE PROPOSE TO IMPROVE RRTMGP TO SUPPORT GEOS-5 NATURE RUNS AT HIGH SPATIAL RESOLUTION A CRITICAL PRIORITY FOR GMAO BOTH BY INCLUDING THE IMPACT OF TOPOGRAPHY ON RADIATIVE FLUXES AND BY IMPLEMENTING STRATEGIES TO SPEED UP THE CODE. WE WILL ALSO ENHANCE RRTMGP TO ALLOW SOLAR VARIABILITY TO BE SIMULATED MORE ACCURATELY IN GEOS-5 TO INCLUDE THE RADIATIVE EFFECTS OF KEY HYDROFLUOROCARBONS TO ACCURATELY COMPUTE THE RADIATION FROM MASSIVE EMISSIONS OF SULFUR DIOXIDE FROM LARGE VOLCANIC ERUPTIONS AND TO EXTEND THE UPPER VERTICAL LIMIT OF THE CODE ABOVE 65 KM. RRTMGP ALSO INCLUDES A SATELLITE SIMULATION CAPABILITY AND WE PROPOSE TO ADD CRIS AIRS IASI AND OCO-2 TO THE SUITE OF IMPLEMENTED SENSORS. THIS DEVELOPMENT WILL SIGNIFICANTLY ENHANCE THE GEOS-5 REPRESENTATION OF RADIATIVE PROCESSES OF CRITICAL IMPORTANCE ACROSS A WIDE RANGE OF SPATIAL AND TEMPORAL SCALES. THIS WORK WOULD THEREBY SUPPORT THE MAP PROGRAM OBJECTIVE OF ATTAINING A COMPLETE UNDERSTANDING OF THE EARTH SYSTEM AS WELL AS ENHANCE THE QUALITY OF GEOS-5 SIMULATIONS AND REANALYSIS PRODUCTS PRODUCED BY THE MODEL. THESE BENEFITS WOULD APPLY ACROSS THE WEATHER-TO-CLIMATE CONTINUUM OF TEMPORAL SCALES AND EXTEND TO MAP PROJECTS RELATED TO GEOS-5 SUCH AS THE GLOBAL MODELING INITIATIVE AND THE NASA UNIFIED WEATHER RESEARCH FORECAST MODEL. THIS PROPOSAL WILL IMPROVE A COMPONENT OF NASA MAP SUPPORTED MODELS A PROGRAMMATIC PRIORITY IDENTIFIED IN THIS SOLICITATION AND IT IS RELEVANT TO THE RESEARCH THEMES IN THE SOLICITATION OF ASSIMILATION COUPLING IN THE EARTH SYSTEM CONSTITUENTS IN THE CLIMATE SYSTEM AND PREDICTABILITY IN THE EARTH SYSTEM.