Midsummer Low-Level Circulation and Precipitation in Subtropical South America and Related Sea Surface Temperature Anomalies in the South Atlantic

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Abstract
The midsummer interannual variability of the low-level tropospheric circulation and of the precipitation field in subtropical South America (SA) associated to the sea surface temperature (SST) anomalies in the western subtropical South Atlantic Ocean (WSSA) is investigated using reanalyses, regional precipitation datasets, and monthly SSTs. The region of the WSSA where SST has the strongest relation with precipitation in subtropical SA was identified using canonical correlation analysis. This region extends from 20° to 30°S and from 30° to 50°W. Composites corresponding to extreme SSTs in this area show two well-differentiated patterns in the low-level circulation and in the precipitation fields. In the composite, corresponding to the more positive SST anomalies in this area, the mainstream of the low-level flow and of the moisture transport from the continental low latitudes starts to follow a southeastward direction at 10°S, and converges with the west flow at 35°S over the Atlantic Ocean. On t... Abstract The midsummer interannual variability of the low-level tropospheric circulation and of the precipitation field in subtropical South America (SA) associated to the sea surface temperature (SST) anomalies in the western subtropical South Atlantic Ocean (WSSA) is investigated using reanalyses, regional precipitation datasets, and monthly SSTs. The region of the WSSA where SST has the strongest relation with precipitation in subtropical SA was identified using canonical correlation analysis. This region extends from 20° to 30°S and from 30° to 50°W. Composites corresponding to extreme SSTs in this area show two well-differentiated patterns in the low-level circulation and in the precipitation fields. In the composite, corresponding to the more positive SST anomalies in this area, the mainstream of the low-level flow and of the moisture transport from the continental low latitudes starts to follow a southeastward direction at 10°S, and converges with the west flow at 35°S over the Atlantic Ocean. On t...

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