EMISSIONS OF SHORT-LIVED AIR POLLUTANTS WITH DETECTABLE SATELLITE-OBSERVED PLUMES INCLUDING SO2 AND NOX CAN BE ESTIMATED DIRECTLY FROM SATELLITE OBSERVATIONS. SATELLITES HAVE OBSERVED SIGNIFICANT CHANGES IN AIR POLLUTANT CONCENTRATIONS DRIVEN BY ANTHROPOGENIC EMISSIONS THAT CAN VARY OVER SHORT PERIODS OWING TO FOR EXAMPLE THE OPENING OF NEW INDUSTRIAL FACILITIES OR THE IMPLEMENTATION OF STRICTER EMISSION CONTROLS. AIR QUALITY AND CLIMATE MODELS TYPICALLY USE BOTTOM-UP EMISSION INVENTORIES COMPILED BY AGGREGATING ACTIVITY DATA AND EMISSION FACTORS WHICH DO NOT ALWAYS REFLECT RECENT CHANGES LEADING TO INACCURATE MODEL RESULTS. WE WILL PIONEER AN IN-DEPTH COLLABORATION BETWEEN THE SATELLITE RESEARCH COMMUNITY AND EMISSION INVENTORY DEVELOPERS TO MERGE THE BEST FEATURES OF SATELLITES AND BOTTOM-UP INVENTORIES. WE WILL INNOVATIVELY MERGE NEW SATELLITE-DERIVED EMISSIONS WITH A STATE-OF-THE-SCIENCE GLOBAL INVENTORY TO PROVIDE MORE ACCURATE AND TIMELY EMISSIONS FOR IMPROVED ANALYSIS OF ATMOSPHERIC COMPOSITION. WE WILL DEVELOP THE NASA SATELLITE-DERIVED EMISSION (SATEM) DATABASE TO QUANTIFY SO2 AND NOX EMISSIONS AT ENHANCED ACCURACY AND TEMPORAL RESOLUTION FROM LATEST OZONE MONITORING INSTRUMENT (OMI) RETRIEVALS. USING AN UPDATED EMISSIONS QUANTIFICATION METHOD TOGETHER WITH THE LATEST SATELLITE DATA PRODUCTS SATEM WILL BE THE MOST COMPREHENSIVE AND ACCURATE CATALOG OF NOX AND SO2 GLOBAL EMISSION SOURCES YET TO BE PRODUCED. WE WILL ALSO USE THE EUROPEAN SPACE AGENCY (ESA) TROPOSPHERIC MONITORING INSTRUMENT (TROPOMI) RETRIEVALS TO ADD SEASONAL DETAIL TO THE POINT SOURCE EMISSIONS DATABASE. WE WILL THEN MERGE SATEM WITH A LEADING GLOBAL BOTTOM-UP INVENTORY THE COMMUNITY EMISSIONS DATA SYSTEM (CEDS) TO CONSTRUCT A HYBRID LONG-TERM GLOBAL ANTHROPOGENIC EMISSION INVENTORY CEDS-SATEM EXTENDING TO THE CURRENT YEAR. THIS HYBRID INVENTORY COMBINES THE COMPREHENSIVE NATURE OF THE BOTTOM-UP EMISSIONS DATA WITH THE SATEM LARGE-SOURCE EMISSIONS DATABASE (MAGNITUDE SPATIAL LOCATION ANNUAL TIME SERIES AND SEASONALITY) TO FORM THE MOST ACCURATE POSSIBLE ESTIMATE OF ANTHROPOGENIC EMISSIONS INTO THE ATMOSPHERE. SO2 AND NOX HAVE PROFOUND IMPACTS ON AIR QUALITY AND CLIMATE AS THE PRINCIPAL PRECURSORS OF OZONE AND AEROSOLS. OUR MORE ACCURATE EMISSION INVENTORY OF SO2 AND NOX WILL ALLOW IMPROVED SIMULATIONS OF OZONE AND FINE PARTICULATE MATTER AND THEREFORE ATMOSPHERIC COMPOSITION. WE WILL IMPLEMENT THE CEDS-SATEM MERGED EMISSION INVENTORY IN THE NASA GODDARD EARTH OBSERVING SYSTEM (GEOS) MODEL TO BOTH EVALUATE THE RESPONSE OF SPATIOTEMPORAL VARIATIONS IN TROPOSPHERIC AIR QUALITY TO EMISSIONS CHANGES OVER THE OMI ERA FOCUSING ON REGIONS WHERE EMISSIONS ARE NOT WELL CHARACTERIZED IN BOTTOM-UP INVENTORIES AND TO EVALUATE THE IMPACT OF THE IMPROVED EMISSIONS INVENTORY ON MODEL RESULTS. OUR PROPOSAL IS HIGHLY RELEVANT TO THE ROSES A.19 SOLICITATION AS IT HELPS TO ADDRESS THE QUESTION HOW IS ATMOSPHERIC COMPOSITION CHANGING. SPECIFICALLY WE ADDRESS LONG-TERM TRENDS IN ATMOSPHERIC COMPOSITION BY EMPLOYING BOTH OMI AND TROPOMI DATA SETS. THE IMPROVED LONG-TERM EMISSION INVENTORIES FOR SO2 AND NOX FROM THIS PROJECT WILL FACILITATE THE THE ATTRIBUTION OF CHANGES IN AIR QUALITY ENCOURAGED IN AREA A AND ENABLE ENHANCED OZONE AND AEROSOL FORECASTS IN AIR QUALITY AND CHEMISTRY-CLIMATE MODELS BOTH THROUGH THE ACTIVITIES OUTLINED IN THIS PROPOSAL AND MORE BROADLY BY MAKING THE HYBRID SATELLITE-DERIVED/BOTTOM-UP INVENTORY PUBLICLY AVAILABLE. OUR PROPOSED HYBRID INVENTORY METHODOLOGY WILL HAVE EVEN WIDER APPLICATION AND SMALLER UNCERTAINTIES WHEN MEASUREMENTS FROM THE NEXT-GENERATION GEOSTATIONARY SATELLITES INCLUDING KOREA AEROSPACE RESEARCH INSTITUTE (KARI) GEMS (GEOSTATIONARY ENVIRONMENT MONITORING SPECTROMETER) ESA SENTINEL-4 AND NASA TEMPO (TROPOSPHERIC EMISSIONS: MONITORING OF POLLUTION) ARE AVAILABLE.