VARIABILITY AND TRENDS IN TROPOSPHERIC OXIDATION: INTERACTIONS WITH REGIONAL AIR QUALITY, GLOBAL ATMOSPHERIC COMPOSITION, AND CLIMATE

VARIABILITY AND TRENDS IN TROPOSPHERIC OXIDATION: INTERACTIONS WITH REGIONAL AIR QUALITY GLOBAL ATMOSPHERIC COMPOSITION AND CLIMATETRENDS AND VARIABILITY IN THE OXIDIZING CAPACITY OF THE TROPOSPHERE CAN ALTER THE LIFETIMES OF NEAR-TERM CLIMATE FORCERS AIR POLLUTANTS AND SOME STRATOSPHERIC OZONE DEPLETING SUBSTANCES (E.G. METHANE OZONE AEROSOLS HYDROCHLOROFLUOROCARBONS). THE GLOBAL TROPOSPHERIC OXIDATION CAPACITY IS LARGELY CONTROLLED BY THE AVAILABILITY OF HYDROXYL RADICAL (OH) CLOSELY COUPLED TO TROPOSPHERIC OZONE A PRIMARY SOURCE OF OH VIA PHOTOLYSIS IN THE PRESENCE OF WATER VAPOR. TROPOSPHERIC OZONE IS ALSO A POTENT GREENHOUSE GAS IN THE UPPER TROPOSPHERE AND A BIOLOGICAL IRRITANT IN SURFACE AIR. IN POLLUTED REGIONS OZONE PRODUCTION CAN OCCUR UNDER DISTINCT CHEMICAL REGIMES WITH STRONG SENSITIVITY TO EITHER OR BOTH EMISSIONS OF NITROGEN OXIDES (NOX) AND ANTHROPOGENIC VOLATILE ORGANIC COMPOUNDS (AVOC). WHERE BIOGENIC EMISSIONS ARE ABUNDANT REGIONAL OZONE POLLUTION IS MOST SENSITIVE TO REDUCTIONS IN NOX EMISSIONS BUT SOME URBAN AREAS ARE ADDITIONALLY SENSITIVE TO AVOC EMISSIONS. IDENTIFYING THESE CHEMICAL REGIMES AND TRACKING THEIR CHANGES OVER TIME CAN PROVIDE INSIGHTS INTO THE EFFICACY OF PAST CURRENT AND FUTURE EMISSION CONTROL PROGRAMS. OUR OVERARCHING GOAL IS TO ADVANCE OUR PROCESS-LEVEL UNDERSTANDING OF OXIDATION CHEMISTRY UNDER VARIOUS CONDITIONS IN THE GLOBAL TROPOSPHERE. WE ALSO SEEK TO IDENTIFY TRENDS AND VARIABILITY IN OXIDATION REGIMES INDUCED BY CHANGES IN POLLUTANT EMISSIONS (ANTHROPOGENIC BIOMASS BURNING) DURING THE LAST TWO DECADES AS WELL AS BY CLIMATE VARIABILITY. BY APPLYING A HIERARCHY OF MODELS TO ANALYZE MULTIPLE PRODUCTS RETRIEVED FROM INSTRUMENTS ABOARD NASA AURA AND OTHER SATELLITES COMBINED WITH SUBORBITAL MEASUREMENTS WE WILL INVESTIGATE OXIDATION IN THREE SELECTED REGIMES: POLLUTED REGIONS REMOTE BACKGROUND DOMINATED BY METHANE AND CARBON MONOXIDE OXIDATION AND AGED BIOMASS BURNING PLUMES TRANSPORTED OVER OCEANS. SPECIFICALLY WE PROPOSE TO: FURTHER DEVELOP A QUANTITATIVE BASIS FOR USING MONTHLY SATELLITE-DERIVED FORMALDEHYDE-TO-NITROGEN DIOXIDE COLUMN RATIOS (HCHO:NO2) AS AN INDICATOR FOR GROUND-LEVEL OZONE PRODUCTION CHEMISTRY WITH A FOCUS ON THE NORTHEASTERN U.S.A. AND ASSEMBLE A U.S.A.-WIDE RECORD OF HCHO:NO2 FOR 1995-PRESENT. INVESTIGATE KEY FACTORS AFFECTING INTER-ANNUAL VARIABILITY IN OH WITHIN THE REMOTE ATMOSPHERE (WHERE METHANE AND CARBON MONOXIDE ARE THE MAIN OH SINKS) INCLUDING THE SENSITIVITY OF OH TO NOY ABUNDANCES AND PARTITIONING AND AN INVESTIGATION OF THE EXTENT TO WHICH HCHO DISTRIBUTIONS REFLECT VARIATIONS IN OH. EXAMINE THE ROLE OF AEROSOLS PARTICULARLY THOSE ASSOCIATED WITH BIOMASS BURNING IN AFFECTING OXIDATION IN POLLUTED AND REMOTE ATMOSPHERIC CONDITIONS THROUGH BOTH RADIATIVE AND CHEMICAL PATHWAYS. CONSTRUCT A SEASONAL CLIMATOLOGY OF OH SENSITIVITY TO DRIVING FACTORS THAT MAY BE USED TO AID IN IDENTIFYING SOURCES OF INTER-MODEL OH DIFFERENCES AND IN PRIORITIZING OBSERVING STRATEGIES TO DETECT CHANGES IN ATMOSPHERIC OXIDATION. OUR PROPOSED WORK IS A KEY STEP TOWARDS CONSTRUCTING A THREE-DIMENSIONAL SEASONAL CLIMATOLOGY OF THE SENSITIVITY OF TROPOSPHERIC OH TO INDIVIDUAL FACTORS AND ADVANCING OUR KNOWLEDGE OF THE DISTRIBUTIONS TRENDS AND VARIABILITY IN NEAR-TERM CLIMATE FORCING AGENTS (E.G. OZONE AEROSOLS AND THEIR PRECURSORS) OF DIRECT RELEVANCE TO NASA INTERESTS SUMMARIZED IN THIS SOLICITATION. MORE BROADLY THIS INFORMATION CAN GUIDE THE DEVELOPMENT OF OPTIMAL SPACE-BASED AND SUBORBITAL OBSERVING SYSTEMS FOR DETECTING FUTURE CHANGES IN ATMOSPHERIC COMPOSITION OF RELEVANCE FOR CLIMATE.