WE PROPOSE TO USE EXISTING MODELS AND NASA OBSERVATIONS TO CARRY OUT THE FOLLOWING RESEARCH TASKS:1) EVALUATE AND IMPROVE THE REPRESENTATION WITHIN AIR QUALITY MODELS OF THE RELATION BETWEEN SURFACE O3 NOX AND VOCS USING NASA OBSERVATIONS OF NO2 AND HCHO (AND RELATED SPECIES) ACQUIRED BY SATELLITE (OMI) AND SUB-ORBITAL CAMPAIGNS (DC3 DISCOVER-AQ SEAC4RS AND SENEX) WITH A FOCUS ON THE TRANSITION FROM THE VOC CONTROL TO THE NOX CONTROL REGIME OF SURFACE OZONE PRODUCTION;2) COMPUTE THE STRATOSPHERIC BURDEN OF BRO BASED ON EMERGING KNOWLEDGE OF CROSS TROPOPAUSE INJECTION OF INORGANIC AND ORGANIC BROMINE FROM MEASUREMENTS ACQUIRED IN THE TROPICAL WESTERN PACIFIC DURING THE NASA ATTREX AND NSF CONTRAST CAMPAIGNS TO ENABLE REALISTIC BURDENS OF POLAR TROPOSPHERIC BRO TO BE QUANTIFIED.THE FIRST TASK WILL UTILIZE NASA OBSERVATIONS TO TEST AND IMPROVE REGULATORY AIR QUALITY MODELS USED IN DEVELOPMENT OF THE STATE IMPLEMENTATION PLANS (SIPS) BEING SUBMITTED TO THE U.S. ENVIRONMENTAL PROTECTION AGENCY (EPA) BY MARYLAND AND OTHER MEMBER STATES OF THE OZONE TRANSPORT COMMISSION (OTC). THESE SIPS DETAIL THE REGULATION OF BOTH IN-STATE AND OUT OF STATE POLLUTANT SOURCES TO ASSURE ATTAINMENT OF THE FEDERALLY MANDATED STANDARDS FOR O-3 AND ITS PRECURSORS. THIS TASK USES "NASA DATA SETS TO STUDY TROPOSPHERIC AIR QUALITY" AND ALSO SERVES TO "MERGE THE ACTIVITIES OF THE ATMOSPHERIC COMPOSITION RESEARCH COMMUNITY AND AIR QUALITY MONITORING ACTIVITIES OF OTHER AGENCIES IN THE U.S." AS DESCRIBED IN THE NRA.THE SECOND TASK WILL UTILIZE NASA OBSERVATIONS TO OBTAIN AN EMPIRICAL DETERMINATION OF THE IMPACT ON TOTAL COLUMN BRO SUPPLIED BY TWO DISTINCTLY DIFFERENT SOURCES: INORGANIC RELEASE FROM THE HIGH LATITUDE SURFACE VERSUS ORGANIC RELEASE IN THE TROPICAL OCEAN. THE ULTIMATE GOAL OF THIS TASK IS TO ASSESS THE PROCESSES THAT CONTROL THE SPRINGTIME PHENOMENON KNOWN AS THE BROMINE EXPLOSION WHICH LEADS TO NEAR COMPLETE REMOVAL OF SURFACE OZONE GREATLY ALTERING THE OXIDATIVE CAPACITY OF THIS REGION OF THE POLAR BOUNDARY LAYER DURING ARCTIC SPRING. THIS TASK USES "AURA DATA TO TRACK CHANGES IN STRATOSPHERIC AND TROPOSPHERIC COMPOSITION" INVOLVES QUANTIFICATION OF THE "EXCHANGE OF TRACE GASES" BETWEEN THE TROPOSPHERE AND STRATOSPHERE AND USES AURA MEASUREMENTS TO QUANTIFY THE REASON FOR A SHARP DECLINE IN THE "OXIDATION EFFICIENCY" DURING ARCTIC SPRING AS DESCRIBED IN THE NRA.OUR PROPOSAL BUILDS ON OUR GROUP'S PRIOR WORK WITH NASA SATELLITE DATA AND VARIOUS FIELD CAMPAIGNS (SUMMARIZED HEREIN) AND COMPLEMENTS AN ON-GOING IN SITU OBSERVATION AND AIR QUALITY SIMULATION EFFORT CONDUCTED BY OUR GROUP UNDER THE REGIONAL ATMOSPHERIC MEASUREMENT MODELING AND PREDICTION PROGRAM (RAMMPP) THAT IS SPONSORED BY THE MARYLAND DEPARTMENT OF THE ENVIRONMENT (MDE).