A Statistical Analysis of Lightning NOx Production Based on Measurements from TROPOMI and GLM

NO_x (NO + NO₂) is a critical trace gas in the earth's atmosphere that plays an essential role in controlling concentrations of ozone and other important greenhouse gases like methane. The principle source is lightning, and quantifying the amount of lightning-produced NO_x (LNO_x) is an ongoing problem in atmospheric chemistry. Increasingly, satellites have become valuable tools in such investigations, particularly for determining the NO production efficiency (PE) of individual lightning strokes. Some studies have combined NO₂ satellite measurements from instruments such as the Ozone Monitoring Instrument (OMI) with ground-based lightning data from networks like the World Wide Lightning Location Network (WWLLN) to determine PE values. The current pilot study is based on the new high-quality NO₂ data from the Tropospheric Monitoring Instrument (TROPOMI) and satellite lightning data from the Geostationary Lightning Mapper (GLM). TROPOMI, with its nadir resolution of 3.5 x 7 km² and GLM, with a flash detection efficiency (DE) several times higher than that of WWLLN represent significant advances over earlier instruments. We apply retrieval algorithms like those in OMI/WWLLN studies to measurements over the United States during the boreal summer of 2019. The algorithms include subtraction of stratospheric NO₂ amounts from total-column NO₂ over deep convection and employ a priori air mass factors (AMFs) to estimate LNO_x amounts. Comparing these amounts on large temporal-spatial scales with lightning flash-counts yields statistical estimates of PE. We examine implications of our findings in the context of previous studies, some of which have shown a dependence of PE on flash-rate.