[A-AS11] Atmospheric Chemistry

[AAS11-14] Examination of a method to detect nitrogen oxides originated from lightning by the combined use of ground-based and satellite remote sensing

*Yukino Fujii¹, Hitoshi Irie¹ (1.Chiba University)

Keywords:Lightning NOx, Ground-based and satellite observations

In recent years, there has been a growing concern about climate change and air pollution. Nitrogen oxides (NOx), recently also known as one of the Short Lived Climate Forcers (SLCFs), are not only an air pollutant but also a precursor of photochemical oxidants such as ozone, affecting human health, agricultural products, and climate. With this importance, the dominant source of NOx in the middle and upper troposphere is NOx originated from lightning (Lightning NOx; LNOx). It has been estimated that the amount of LNOx released into the atmosphere accounts for 10% of the total amount of global NOx emissions. However, the observation data for the evaluation of LNOx is limited. To overcome this problem, this study attempted to examine a method for detecting LNOx by combining ground-based remote sensing observation MAX-DOAS (Multi-Axis Differential Optical Absorption Spectroscopy) and satellite observation TROPOMI (TROPOspheric Monitoring Instrument). We focus on the period from July 26 to August 8, 2021, during which the intensive observation campaign called Chiba Campaign was held. Analysis of the tropospheric NO₂ column concentration data from both observations revealed that the tropospheric NO₂ column concentration was relatively low on July 31 and August 7, and that the lower troposphere was not strongly affected by anthropogenic emissions. In addition, the tropospheric NO₂ column concentration of TROPOMI tended to be higher than that of MAX-DOAS on both days. This is thought to reflect the increase in NO₂ in the middle and upper troposphere because MAX-DOAS observation is less sensitive to the middle and upper troposphere. To confirm this, we used data from LIghtning DEtection Network system (LIDEN) and backward trajectory analysis. On July 31, it was found that an air mass at an altitude of 12 and 13 km passed through the place where lightning occurred 24-30 hours prior to the observation. On August 7, it was found that an air mass at an altitude of 14 km had passed the place where lightning occurred an hour before the observation. From these results, it was found that the identified increase in NO₂ concentration in the middle and upper troposphere may be affected by LNOx.