Lightning Source of Nitrogen Oxides (NO _x ) Inferred From Geostationary Satellites: Global Implications for Oxidant Chemistry

Abstract

Lightning is a major source of nitrogen oxide radicals (NO _x  ≡ NO + NO ₂ ), but large uncertainties in NO _x yields per flash hinder accurate quantification of emissions and impacts on oxidant chemistry. We use 1 year of concurrent geostationary satellite observations of free tropospheric (FT) NO ₂ from TEMPO and flash rates from GLM to show that lightning is the dominant source of FT NO _x over North America. The observed FT NO ₂ and its correlation with flash rates imply a NO _x yield of 150 ± 60 mol N flash ⁻¹ . Applying this yield globally in the GEOS‐Chem atmospheric chemistry model reduces lightning NO _x emissions from 6.6 to 3.2 Tg N yr ⁻¹ . This generally improves simulated NO _x , ozone, and hydroxyl radical in comparison with satellite and in situ measurements, though with some regional overcorrections for ozone. The methane lifetime against tropospheric OH increases from 8.7 to 9.4 years, partially reducing the gap with the best empirical estimate (11 years).