Significant contribution of lightning NO to summertime surface O on the Tibetan Plateau.

Lightning generates nitrogen oxides (NO) in the troposphere, an important precursor of tropospheric ozone (O). The Tibetan Plateau (TP) is considered to be a global atmospheric background location with limited anthropogenic influences. However, the observed summertime surface O concentration on the TP is 25% higher than that in highly polluted regions (e.g., southern China). Previous studies have suggested that lightning-produced NO (LNO) can affect the concentration of surface O. We used the Weather Research and Forecasting coupled with chemistry (WRF-Chem) model combined with satellite, ground-based, and airborne observations to evaluate the contribution of LNO to the surface O budget on the TP. Our results showed that LNO contributed approximately 15% of the surface NO emission on the TP in summer. Accordingly, the contribution of LNO to the summertime surface daily maximum 8-h average (MDA8) O on the TP was 9.3 ± 7.1 ppb, which was 17.5% ± 14.5% of the total concentration of the surface MDA8 O. In addition, our study found that the number of moles of NO produced per lightning flash (LNO production efficiency) significantly affected the surface concentration of NO, OH, and MDA8 O. Increasing the LNO production efficiency (PE) from 0 to 330 mol NO flash increased the concentration of MDA8 O by up to 20% on the TP. Our study revealed that lightning significantly affects the atmospheric chemical processes involving O on the TP.