USING MULTI-SATELLITE OBSERVATIONS TO ANALYZE GROUND-LEVEL OZONE SENSITIVITY TO NOX AND VOC PRECURSOR EMISSIONS, FROM URBAN TO GLOBAL SCALES

AMBIENT EXPOSURE TO GROUND-LEVEL OZONE IS ESTIMATED TO CAUSE MORE THAN 250 000 GLOBAL PREMATURE DEATHS PER YEAR. GROUND-LEVEL OZONE IS PRODUCED FROM PHOTOCHEMICAL REACTIONS BETWEEN ITS PRECURSORS: NITROGEN OXIDES (NOX) AND VOLATILE ORGANIC COMPOUNDS (VOCS). OZONE FORMATION DEPENDS NONLINEARLY ON THE RELATIVE AVAILABILITY OF ITS PRECURSORS. IDENTIFYING THE LIMITING SPECIES FOR OZONE FORMATION (I.E. NOX-LIMITED OR VOC-LIMITED) ESPECIALLY ITS SPATIAL AND TEMPORAL VARIABILITY HAS BEEN A MAJOR CHALLENGE BUT IS NEEDED FOR THE DESIGN OF COST-EFFECTIVE EMISSION CONTROL POLICIES. WHILE CURRENT SATELLITE INSTRUMENTS CANNOT RETRIEVE GROUND-LEVEL OZONE ABUNDANCES THEY HAVE PROVIDED CONTINUOUS AND RELIABLE GLOBAL OBSERVATIONS OF OZONE PRECURSORS NAMELY NO2 AND FORMALDEHYDE (HCHO A PROXY FOR VOCS) FOR OVER TWO DECADES. PREVIOUS WORK INCLUDING OUR OWN HAS DEMONSTRATED THAT THE RATIO OF TROPOSPHERIC COLUMN DENSITY OF HCHO TO NO2 OBSERVED FROM SATELLITES CAN BE USED TO CHARACTERIZE OZONE SENSITIVITY. BUILDING UPON PREVIOUS WORK I AIM TO FACILITATE THE APPLICATION OF SATELLITE REMOTE SENSING TO IDENTIFY THE COMPLEXITIES OF OZONE CHEMISTRY AT DIFFERENT SPATIAL (FROM URBAN TO GLOBAL) AND TEMPORAL SCALES (FROM DAILY TO DECADAL). SPECIFICALLY I PROPOSE TO: 1) CONSTRUCT AT LEAST 20-YEAR (1996 TO 2016) GLOBAL HARMONIZED AND SPACE-BASED TIME SERIES OF HCHO/NO2 FROM FOUR SATELLITES INCLUDING GOME SCIAMACHY GOME-2 OMI AND ANALYZE THE LONG-TERM TREND OF THIS INDICATOR FOR OZONE SENSITIVITY OVER MAJOR ANTHROPOGENIC SOURCE REGIONS. I WILL THEN ASSESS HOW TRENDS IN HCHO/NO2 RELATE TO LONG-TERM CHANGES IN SURFACE OZONE AT BOTH LOCAL AND REGIONAL SCALES USING GROUND-BASED OBSERVATIONS FROM THE TROPOSPHERIC OZONE ASSESSMENT REPORT (TOAR) DATABASE. 2) USE PRODUCTS RETRIEVED FROM THE RECENTLY LAUNCHED TROPOMI INSTRUMENT TO REFINE THE COARSE RESOLUTION AND LOW DAILY DATA COVERAGE OF OMI PRODUCTS. I WILL ANALYZE FINE SPATIAL PATTERNS OF NO2 HCHO AND OZONE SENSITIVITY AT THE SUB-URBAN SCALES RETRIEVED FROM TROPOMI AND DIAGNOSE VARIATIONS IN OZONE SENSITIVITY TO PRECURSOR EMISSIONS DURING THE HIGHEST OZONE EVENTS. 3) BUILD QUANTITATIVE RELATIONSHIPS BETWEEN SATELLITE HCHO/NO2 AND OZONE SENSITIVITIES TO PRECURSOR EMISSIONS ESTIMATED BY THE HEMISPHERIC TRANSPORT OF AIR POLLUTION (HTAP) MODEL ENSEMBLE. I WILL THEN USE LONG-TERM AND FINE-SCALE SATELLITE PRODUCTS TO DOWNSCALE SPATIALLY AND TO EXPAND TEMPORALLY THE COARSE SINGLE-YEAR MULTI-MODEL ENSEMBLE TO ASSESS OZONE RESPONSES TO ANTHROPOGENIC NOX OR NMVOC EMISSION REDUCTIONS AT 0.1 DEGREE RESOLUTION FROM 1996 TO 2016. THE PROPOSED INNOVATIVE USE OF SATELLITE DATA BRIDGES BASIC RESEARCH IN ATMOSPHERIC COMPOSITION BY ADVANCING THE STATE-OF-THE-SCIENCE ON OZONE POLLUTION FROM URBAN TO GLOBAL SCALES AND APPLIED RESEARCH FOR AIR QUALITY MANAGEMENT BY PROVIDING INFORMATION TO POLICY MAKERS REGARDING WHICH CLASS OF EMISSION REDUCTIONS WILL BE MOST COST-EFFECTIVE FOR REDUCING SURFACE OZONE LEVELS. THE PROPOSED STUDY ALSO ALIGNS WITH THE TOAR AND HTAP ASSESSMENT ACTIVITIES BY RE-ASSESSING MODELED OZONE SENSITIVITIES TO PRECURSOR EMISSIONS ALONGSIDE OBSERVED OZONE TRENDS. THE USE OF TROPOMI DATA WILL PIONEER THE APPLICATION OF NEW GENERATION SATELLITES FOR OZONE POLLUTION AND LAY A FOUNDATION FOR FUTURE APPLICATIONS WITH GEOSTATIONARY PLATFORMS