WE PROPOSE TO CONTINUE OUR WORK ON THE AURA SCIENCE TEAM AND WITH ACMAP TO DEMONSTRATE THE VALUE OF AURA AND COMPLEMENTARY DATA FOR ATMOSPHERIC CHEMISTRY APPLICATIONS USING THE GEOS-CHEM CHEMICAL TRANSPORT MODEL (CTM) AS AN ANALYSIS TOOL. WE ALSO REQUEST CONTINUED FUNDING FOR THE GEOS-CHEM SUPPORT TEAM AT HARVARD TO MANAGE GEOS-CHEM AS AN OPEN-ACCESS MODEL FOR A LARGE WORLDWIDE USER COMMUNITY AND WITH STRONG SCIENTIFIC RETURN TO NASA. OUR WORK ON THE AURA SCIENCE TEAM WILL MESH WITH ACMAP S INTERESTS BY USING NEW AND NEWLY VALIDATED OMI DATA SETS TO IMPROVE OUR UNDERSTANDING OF PROCESSES CONTROLLING AIR QUALITY AND THE GLOBAL BUDGET OF TROPOSPHERIC OZONE. WE WILL FOCUS ON THREE TASKS: 1. APPLY A HIGH-RESOLUTION ADJOINT-BASED INVERSION TO OMI OBSERVATIONS OF FORMALDEHYDE (HCHO) AND GLYOXAL (CHOCHO) OVER THE EASTERN US TO BETTER QUANTIFY ISOPRENE EMISSIONS AND DEMONSTRATE A NEW LEVEL OF CAPABILITY IN THE USE OF HCHO AND CHOCHO DATA FROM SPACE; 2. IMPROVE THE VALUE OF OMI NO2 OBSERVATIONS FOR QUANTIFYING NOX EMISSIONS THROUGH BETTER UNDERSTANDING OF THE FREE TROPOSPHERIC CONTRIBUTION TO THE NO2 COLUMN WITH APPLICATION TO ADDRESSING UNCERTAINTIES IN US NOX EMISSIONS; 3. IMPROVE UNDERSTANDING OF THE FACTORS CONTROLLING GLOBAL TROPOSPHERIC OZONE BY INTERPRETING OMI OZONE OBSERVATIONS TOGETHER WITH NEW CLOUD-SLICED OMI PRODUCTS FOR FREE TROPOSPHERIC NO2 AND BRO AND WITH ADDITIONAL INFORMATION FROM OZONE DATA ASSIMILATION USING GEOS-CHEM IN THE GODDARD EARTH OBSERVING SYSTEM (GEOS) DATA ASSIMILATION SYSTEM (DAS) AT THE NASA GLOBAL MODELING AND ASSIMILATION OFFICE (GMAO). CONTINUED ACMAP FUNDING FOR THE GEOS-CHEM SUPPORT TEAM (1 FTE) WILL ENABLE US TO SUSTAIN GEOS-CHEM AS A STATE-OFSCIENCE OPEN-ACCESS USER-FRIENDLY MODEL SERVING A LARGE INTERNATIONAL SCIENTIFIC COMMUNITY IN THE INTERPRETATION OF NASA AND OTHER ATMOSPHERIC OBSERVATIONS. IT WILL SUPPORT (1) STRUCTURAL MODEL DEVELOPMENT (2) IMPLEMENTATION OF NEW SCIENTIFIC DEVELOPMENTS ORIGINATING FROM THE USER COMMUNITY (3) BENCHMARKING AND DOCUMENTATION TO ENSURE MODEL INTEGRITY AND TRACEABILITY AND (4) COMMUNICATIONS AND SERVICE TO USERS. IT WILL DIRECTLY BENEFIT CHEMICAL MODELING AND DATA ASSIMILATION AT GMAO THROUGH THE SEAMLESS CONDUIT BETWEEN THE GEOS-CHEM CTM AND THE GEOS EARTH SYSTEM MODEL (ESM) ENABLED BY THE GEOS-CHEM CHEMICAL MODULE ALREADY IN PLACE IN THE ESM. SUPPORT FOR GEOS-CHEM WILL THUS CONTINUE TO PROVIDE VERY HIGH SCIENTIFIC RETURN TO NASA FOR THE INTERPRETATION OF SATELLITE AND AIRCRAFT OBSERVATIONS FOR THE DEVELOPMENT OF THE NEXT GENERATION OF CLIMATE MODELS AND FOR CHEMICAL DATA ASSIMILATION.