Changes in atmospheric circulation and evapotranspiration are reducing rainfall in the Brazilian Cerrado

Abstract

Here we analyze the trends of rainfall and the frequency of rainy days over the Brazilian Cerrado between 1960 and 2021 in four distinct periods according to the seasonal patterns over the region. We also evaluated trends in evapotranspiration, atmospheric pressure, winds, and atmospheric humidity over the Cerrado to elucidate the possible reasons for the detected trends. We recorded a significant reduction in rainfall and frequency of rainy days in the northern and central Cerrado regions for all periods except at the beginning of the dry season. The most pronounced negative trends were recorded during the dry season and the beginning of the wet season, where we recorded reductions of up to 50% in total rainfall and the number of rainy days. These findings are associated with the intensification of the South Atlantic Subtropical Anticyclone, which has been shifting atmospheric circulation and raising regional subsidence. Moreover, during the dry season and the beginning of the wet season, there was a reduction in regional evapotranspiration, which also potentially contributed to the rainfall reduction. Our results suggest an expansion and intensification of the dry season in the region, potentially bringing broad environmental and social impacts that transcend the Cerrado boundaries.

Spatial heterogeneity in climate change effects across Brazilian biomes

“…Conversely, in scenarios of future deforestation, precipitation reductions are even more pronounced, driven by a negative feedback mechanism. Hofmann et al 62 revealed a significant reduction in both rainfall and the frequency of rainy days in the northern and central regions of the Cerrado for all periods, except at the beginning of the dry season. The most pronounced negative trends were observed during the dry season and the early wet season, with reductions of up to 50% in total rainfall and the number of rainy days.…”

“…The most pronounced negative trends were observed during the dry season and the early wet season, with reductions of up to 50% in total rainfall and the number of rainy days. Hofmann et al 62 attributed to the intensification of the South Atlantic Subtropical Anticyclone, which has altered atmospheric circulation and increased regional subsidence. Additionally, reduced regional evapotranspiration during the dry season and early wet season likely contributed to the observed rainfall reduction.…”

“…Similar results were found for the Cerrado biome. Hofmann et al 62 indicates the impact of changes in evapotranspiration patterns on the Cerrado rainfall regime, and 65 provides evidence that the expansion of cropland in the Cerrado has led to deforestation, which increasingly affects rainfall patterns. Changes in land use and impacts of climate change have significantly impacted river flows in the Cerrado, with large-scale deforestation aimed at the production of irrigated agricultural commodities having a more significant impact on river flows than climate changes, as shown by 57 .…”