Estimates of lightning NO_<i>x</i> production based on high-resolution OMI NO₂ retrievals over the continental US

<p>Lightning serves as the dominant source of nitrogen oxides (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msub><mi mathvariant="normal">NO</mi><mi>x</mi></msub><mo>=</mo><mi mathvariant="normal">NO</mi><mo>+</mo><msub><mi mathvariant="normal">NO</mi><mn mathvariant="normal">2</mn></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="80pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="a1a9a6720bb1e0b9b83931d45ed6d7c4"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-13-1709-2020-ie00001.svg" width="80pt" height="13pt" src="amt-13-1709-2020-ie00001.png"/></svg:svg></span></span>) in the upper troposphere (UT), with a strong impact on ozone chemistry and the hydroxyl radical production. However, the production efficiency (PE) of lightning nitrogen oxides (L<span class="inline-formula">NO_<i>x</i></span>) is still quite uncertain (32–1100&thinsp;mol&thinsp;NO per flash). Satellite measurements are a powerful tool to estimate L<span class="inline-formula">NO_<i>x</i></span> directly compared to conventional platforms. To apply satellite data in both clean and polluted regions, a new algorithm for calculating L<span class="inline-formula">NO_<i>x</i></span> has been developed that uses the Berkeley High-Resolution (BEHR) v3.0B <span class="inline-formula">NO₂</span> retrieval algorithm and the Weather Research and Forecasting model coupled with chemistry (WRF-Chem). L<span class="inline-formula">NO_<i>x</i></span> PE over the continental US is estimated using the <span class="inline-formula">NO₂</span> product of the Ozone Monitoring Instrument (OMI) data and the Earth Networks Total Lightning Network (ENTLN) data. Focusing on the summer season during 2014, we find that the lightning <span class="inline-formula">NO₂</span> (L<span class="inline-formula">NO₂</span>) PE is <span class="inline-formula">32±15</span>&thinsp;mol&thinsp;<span class="inline-formula">NO₂</span> per flash and <span class="inline-formula">6±3</span>&thinsp;mol&thinsp;<span class="inline-formula">NO₂</span> per stroke while L<span class="inline-formula">NO_<i>x</i></span> PE is <span class="inline-formula">90±50</span>&thinsp;mol&thinsp;<span class="inline-formula">NO_<i>x</i></span> per flash and <span class="inline-formula">17±10</span>&thinsp;mol&thinsp;<span class="inline-formula">NO_<i>x</i></span> per stroke. Results reveal that our method reduces the sensitivity to the background <span class="inline-formula">NO₂</span> and includes much of the below-cloud L<span class="inline-formula">NO₂</span>. As the L<span class="inline-formula">NO_<i>x</i></span> 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 L<span class="inline-formula">NO₂</span> to <span class="inline-formula">NO₂</span> is also needed, given its large influence on the estimation of L<span class="inline-formula">NO₂</span> PE.</p>