The Location of Large-Scale Soil Moisture Anomalies Affects Moisture Transport and Precipitation over Southeastern South America

Previous studies have shown that southeastern South America (SESA) is a hot spot for land-atmosphere interactions during austral summer. One mechanism involves dry soil moisture anomalies influencing rainfall through changes in atmospheric circulation. Dry soil moisture anomalies lead to warming at the surface and lower troposphere, increasing the thickness aloft, which changes the intensity and shifts the low-level moisture flux. Few studies, however, have evaluated the sensitivity of the climate response to the location of soil moisture anomalies. In this work, we conducted a control simulation and three experimental simulations using the Community Earth System Model (CESM), prescribing dry soil moisture anomalies over three different locations: (1) SESA, (2) western SESA, and (3) eastern SESA. Preliminary results show that dry SESA and dry eastern SESA runs have similar precipitation responses, while the dry western SESA run shows a different pattern. In the dry western SESA run, the low-level moisture flux is intensified and shifted to the east. In the dry SESA and dry eastern SESA runs, the low-level southward moisture flux is weakened over land but intensified over the ocean. In addition to numerical experiments, we also use the stepwise generalized equilibrium feedback assessment (SGEFA) to isolate the effect of soil moisture anomalies on moisture transport and precipitation. In summary, our results suggest that the location of soil moisture anomalies affects the moisture transport and precipitation response over southeastern South America.