Two Air Quality Regimes in Total Column NO₂ over the Gulf of Mexico in May 2019: Shipboard and Satellite Views

Abstract

The Satellite Coastal and Oceanic Atmospheric Pollution Experiment (SCOAPE) cruise in the Gulf of Mexico (GOM) was conducted in May 2019 by NASA and the Bureau of Ocean Energy Management to determine the feasibility of using satellite data to measure air quality (AQ) in a region of concentrated oil and natural gas (ONG) operations. SCOAPE featured nitrogen dioxide (NO₂ ) instrumentation (Pandora, Teledyne API analyzer) at Cocodrie, LA (29.26°, -90.66°), and on the Research Vessel Point Sur operating off the Louisiana coast with measurements of ozone, carbon monoxide (CO) and volatile organic compounds (VOC). The findings: (1) both satellite and Pandora NO₂ 1 observations revealed two AQ regimes over the GOM, the first influenced by tropical air in 10-14 May, the second influenced by flow from urban areas on 15-17 May; (2) Comparisons of OMI v4 and TROPOMI v1.3 TC (total column) NO₂ data with all Pandora NO₂ column observations on the Point Sur averaged 13% agreement with the largest difference during 15-17 May (~20%). At Cocodrie, LA, at the same time, the satellite-Pandora agreement was ~5%. (3) Three new-model Pandora instruments displayed a TC NO₂ precision of 0.01 Dobson Units (~5%); (4) Regions of smaller and older operations displayed high methane (CH4 ) readings, presumably from leakage; VOC were also detected at high concentrations. Given an absence of regular AQ data in and near the GOM, SCOAPE data constitute a baseline against which future observations can be compared.