Spaceborne Observations of Lightning NO2 in the Arctic

The Arctic region is experiencing notable warming as well as more lightning. Lightning is the dominant source of upper tropospheric nitrogen oxides (NOx), which are precursors for ozone and hydroxyl radicals. In this study, we combine the nitrogen dioxide (NO2) observations from the TROPOspheric Monitoring Instrument (TROPOMI) with Vaisala Global Light-ning Dataset 360 to evaluate lightning NO2 (LNO2) production in the Arctic. By analyzing consecutive TROPOMI NO2 observations, we determine the lifetime and production efficiency of LNO2 during the summers of 2019-2021. Our results show that the LNO2 production efficiency over the ocean is similar to 6 times higher than over continental regions. Additionally, we find that a higher LNO2 production efficiency is often correlated with lower lightning rates. The summertime lightning NOx emission in the Arctic (north of 70 degrees N) is estimated to be 219 +/- 116 Mg of N, which is equal to 5% of anthropogenic NOx emissions. However, for the span of a few hours, the Arctic LNO2 density can even be comparable to anthropogenic NO2 emissions in the region. These new findings suggest that LNO2 can play an important role in the upper-troposphere/lower-stratosphere atmospheric chemical processes in the Arctic, particularly during the summer.

Automated summary

The Arctic region is experiencing significant warming and an increase in lightning frequency. This study combines TROPOMI observations of nitrogen dioxide (NO2) with Vaisala Global Lightning Dataset 360 to evaluate lightning NO2 (LNO2) production in the Arctic. By analyzing consecutive TROPOMI NO2 observations, the researchers determine the lifetime and production efficiency of LNO2 during the summers of 2019-2021. The results show that LNO2 production efficiency is about 6 times higher over the ocean compared to continental regions. Additionally, higher LNO2 production efficiency is often associated with lower lightning rates. The estimated summertime lightning NOx emissions in the Arctic are equal to 5% of anthropogenic NOx emissions, and the density of Arctic LNO2 can even be comparable to anthropogenic NO2 emissions in the region for a few hours. These findings suggest that LNO2 can play an important role in atmospheric chemical processes in the Arctic, particularly during the summer.