Abstract

11 12 Corresponding author: Niko Fedkin ([email protected]) 13 Key Points: 14 • Satellite NO2 records and trends of urban, coastal and deep water areas from 2005 to 15 2022, are presented 16 • Classifying NO2 over the Gulf of Mexico (GOM) under various wind conditions 17 highlights typical patterns in average NO2 values 18 • GOM NO2 hotspots from deepwater platforms were identified by TROPOMI under calm 19 wind conditions, the largest of which is over Mars/Olympus 20 21 Abstract 22 The Outer Continental Shelf of the Gulf of Mexico (GOM) is populated with numerous 23 oil and natural gas (ONG) platforms which produce NOx (NOx = NO + NO2), a major component 24 of air pollution. The Bureau of Ocean Energy Management (BOEM) is mandated to ensure that 25 the air quality of coastal states is not degraded by these emissions. As part of a NASA-BOEM 26 collaboration, we conducted a satellite data-based analysis of nitrogen dioxide (NO2) patterns 27 and trends in the GOM. Data from the OMI and TROPOMI sensors were used to obtain 18+ year 28 records of tropospheric column (TrC) NO2 in three GOM regions: 1) Houston urban area, 2) near 29 shore area off the Louisiana coast, and a 3) deepwater area off the Louisiana coast. The 2004-30 2022 time series show a decreasing trend for the urban (-0.027 DU/decade) and near shore (-31 0.0022 DU/decade) areas, and an increasing trend (0.0019 DU/decade) for the deepwater area. 32 MERRA-2 wind and TROPOMI NO2 data were used to reveal several NO2 hotspots (up to 25% 33 above background values) under calm wind conditions near individual platforms. The NO2 34 signals from these deepwater platforms and the high density of shallow water platforms closer to 35 shore were confirmed by TrC NO2 anomalies of up to 10%, taking into account the monthly TrC 36 NO2 climatology over the GOM. The results presented in this study establish a baseline for future 37 estimates of emissions from the ONG hotspots and provide a methodology for analyzing NO2 38 measurements from the new geostationary TEMPO instrument. 39 40 Plain Language Summary 41 Oil and natural gas operations emit nitrogen oxides (NOx), which are major air pollutants and 42 precursors to ground-level ozone. The Bureau of Ocean Energy Management (BOEM) agency is 43 responsible for managing planned oil and natural gas (ONG) activity on the outer continental 44