Evidence of a link between Amazon fires and lightning

Abstract

The number of fires in the Amazon region increased dramatically at the beginning of 2022 compared to 2021. Considering that this period is also characterized by a large incidence of cloud-to-ground (CG) lightning in this region, we investigated if these phenomena may be related to each other. Two regions of Brazil were considered in the analysis: Mato Grosso state, on the border of the Amazon region where most of the deforestation occurs, and Amazonas state, in the interior of the Amazon region. In the first four months of 2022, 26,554 fires and approximately 3 million CG lightning flashes in Mato Grosso and 2468 fires and about 3.4 million CG lightning flashes in Amazonas were recorded. By comparison, in 2021, 16,844 fires and approximately 2.7 million CG lightning flashes in Mato Grosso and 1258 fires and about 3.2 million CG lightning flashes in Amazonas were recorded. In this study, we examined whether these phenomena were linked on a 2 to 9-day timescale, utilizing wavelet coherence analysis of both fire and lightning data. Our results indicate that these phenomena are linked (p < 0.05) for several weeks in both regions in both years. Additionally, correlations for 2022 were notably higher (above 0.90 versus 0.80) when the incidence of fires and lightning was higher, lending support to the notion of a relationship between these two events. Considering the periodicity characteristics of our results and that most fires in these regions are human-induced, we conclude that anthropogenic fires may affect lightning activity through aerosol-cloud particle interactions, with additional and not previously documented implications for climate change. Assuming the same is happening in other regions of the planet, we may face a new aspect not considered in the present global climate model projections.