第九届青年地学论坛

Lightning-induced nitrogen oxides (LNO_x) can affect ozone (O₃) through photochemical processes. However, the impact of LNO_x on the Tibetan Plateau (TP) O₃ valley, an area with a lower O₃ column compared to surrounding areas, remains controversial. Prior to this study, the impact of monsoonal transport on LNO_x and related effects on the TP O₃ valley has been overlooked. The objectives of this study are to differentiate between locally generated LNO_x and monsoon-transported LNO_x over the TP and to evaluate their impacts on tropospheric NO_x vertical column density, tropospheric column O₃, and O₃ at different altitudes. The Weather Research and Forecasting model coupled with Chemistry model was used to replicate LNO_x, NO_x, and O₃ over the TP during July 2010, for which nesting techniques and sensitivity experiments were implemented. The findings emphasize the importance of LNO_x as a source of NO_x in this region, with nonlocal lightning activity being the primary source. Conversely, the influence of locally generated LNO_x on NO_x levels over the TP is comparatively minor. Overall, LNO_x contributes to an increase in O₃ over the TP, but one order lower than the O₃ depletion. The impact of LNO_x on O₃ varies across different altitude ranges; it is broadly “C” shaped, reflecting increase in O₃ at near-surface and in upper troposphere–lower stratosphere (UTLS) regions and decrease in the middle troposphere. The increase in surface-level O₃ over the TP is mainly caused by monsoon-transported LNO_x, while locally generated LNO_x also plays a crucial role in O₃ formation in the UTLS region.
 

Nitrogen Oxides