Potential Biophysical Processes Associated with Increasing Lightning Strikes in the Arctic Region

Lightning activity in the Arctic has increased significantly in recent years despite an unfavorable cold environment. In the context of climate change, the Arctic amplification's warming effect might be favorable for thunderstorm development. Additionally, vegetation change has been shown to increase thunderstorm activity. This study investigated the biophysical processes associated with Arctic lightning by examining the relationships between vegetation and climatic variables using a cloud-to-ground lightning proxy. The lightning proxy was calculated by multiplying the convective available potential energy (CAPE) by precipitation using European Reanalysis 5th Generation (ERA5) data and was validated against European Cooperation for Lightning Detection (EUCLID) observations. Linear regression analysis over 41 years (1982–2022) revealed significant increases in the summer lightning proxy and Normalized Difference Vegetation Index (NDVI) on the Scandinavian Peninsula. We found a positive correlation between the lightning proxy and NDVI time series, and the causality test confirmed that NDVI is a significant causal factor for the interannual variation of lightning proxy. Correlation and composite difference analyses were conducted using heat, moisture, and dynamic variables to examine the physical linkages between increased NDVI and enhanced lightning strikes. The statistical results suggested that the increased vegetation enhanced the surface solar radiation and thus raised near-surface temperatures. Increased temperatures promoted updrafts and atmospheric instability, which facilitated thunderstorm development. Furthermore, greater evapotranspiration with increased NDVI contributed to increased atmospheric moisture and convergence, which favored updrafts and atmospheric instability. Our findings suggest that increasing vegetation at high latitudes could trigger cascading biophysical processes that promote lightning activity.