Southeastern South America (SESA) is a highly productive agricultural region and a hot spot for land-atmosphere interactions. To evaluate the impact of dry soil moisture anomalies (SMAs) on SESA climate and the sensitivity of the regional climate response to the location of SMAs, we perform three experimental simulations using the Community Earth System Model (CESM) with prescribed dry SMAs over (a) SESA, (b) western SESA, and (c) eastern SESA. The dry SESA and eastern SESA simulations show widespread negative precipitation anomalies. In contrast, the dry western SESA simulation shows positive precipitation anomalies over northeastern Argentina, which are associated with the enhanced southward moisture flux co-located with the South American low-level jet exit region. A composite analysis of extremely dry cases over western SESA using reanalysis data agrees with the findings from our CESM experiment. These findings have potential implications for subseasonal forecasting in this region.

中文翻译：

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大规模土壤湿度异常的位置影响南美洲东南部的水分输送和降水

南美洲东南部（SESA）是一个高产的农业地区，也是陆地与大气相互作用的热点地区。为了评估干燥土壤湿度异常 (SMA) 对 SESA 气候的影响以及区域气候响应对 SMA 位置的敏感性，我们使用社区地球系统模型 (CESM) 进行了三个实验模拟，其中指定的干燥 SMA 超过（a） ) SESA，(b) 西部 SESA，以及 (c) 东部 SESA。干 SESA 和东部 SESA 模拟显示广泛的负降水异常。相比之下，干燥的西部SESA模拟显示阿根廷东北部出现正降水异常，这与南美低空急流出口区域向南的湿气通量增强有关。使用再分析数据对西部 SESA 极端干燥病例进行的综合分析与我们的 CESM 实验结果一致。这些发现对该地区的次季节预测具有潜在影响。