Estimates of Lightning NOx Production based on High Resolution OMI NO2 Retrievals over the Continental US

Lightning serves as the dominant source of nitrogen oxides (NOx = NO + NO2) in the upper troposphere (UT), with strong impact on ozone chemistry and the hydroxyl radical production. However, the production efficiency (PE) of lightning nitrogen oxides (LNOx) is still quite uncertain (32–1100 mol NO per flash). Satellites measurements are a powerful tool to estimate LNOx directly as compared to conventional platforms. To apply satellite data in both clean and polluted regions, a new algorithm for calculating LNOx has been developed based on the program of new Berkeley High Resolution (BEHR) v3.0B NO2 product and the Weather Research and Forecasting-Chemistry (WRF-Chem) model. LNOx PE over the continental US is estimated using the NO2 product of the Ozone Monitoring Instrument (OMI) satellite and the Earth Networks Total Lightning Network (ENTLN) data. Focusing on the summer season during 2014, we find that the lightning NO2 (LNO2) PE is 44 ± 16 mol NO2 flash-1 and 8 ± 3 mol NO2 stroke-1 while LNOx PE is 120 ± 52 mol NOx flash-1 and 22 ± 9 mol NOx stroke-1. Results reveal that former methods are more sensitive to background NO2 and neglect much of the below-cloud LNO2. As the LNOx parameterization varies in studies, the sensitivity of our calculations to the setting of the amount of lightning NO (LNO) is evaluated. Careful consideration of the ratio of LNO2 to NO2 is also needed, given its large influence on the estimation of LNO2 PE.