Local and nonlocal impacts of soil moisture variability in South America

GILES, JULIÁN ALBERTO; MENÉNDEZ, CLAUDIO G.; RUSCICA, ROMINA C.

Conferencia; MeteoXchange ECS Conference; 2022

The land-atmosphere interactions play an important role in modulating climate variability at different spatial and temporal scales. Two recognized soil moisture-atmosphere coupling hot spots are located in southeastern South America (SESA) and eastern Brazil. Soil moisture (SM) variability may not only alter the climate locally, but also have nonlocal impacts through variations in the regional circulation. Here we explore how these local coupling hot spots interact with each other, how SM variability modulates the regional circulation, and which is the nonlocal impact on precipitation. To this end, we analyze numerical experiments with a regional climate model which allow us to isolate the influence of the SM interannual variability on the regional climatology, and we compare results with the ERA5 reanalysis. We propose a nonlocal coupling mechanism that links both hot spots, favoring precipitation in eastern Brazil in detriment of the precipitation in SESA through shifts in the regional circulation, as a consequence of the SM variability. We also analyze particular atmospheric events and the influence of local and nonlocal land-atmosphere coupling during their occurrence in northeastern Argentina, a subregion of SESA located at the exit of the South American low-level jet. It was found that the amount of nighttime precipitation in this subregion is modulated by the proposed nonlocal coupling mechanism. A better understanding of the variability of precipitation due to the influence of land-atmosphere interaction processes may contribute to improving the predictability of precipitation and the interpretation of climate projections.