Influence of tropical Atlantic sea surface temperature anomalies on the East Asian summer monsoon

This study investigates the relationship between tropical Atlantic (TA) sea surface temperature (SST) anomalies and the East Asian summer monsoon (EASM), as well as the possible mechanism by which TA SST anomalies affect the EASM. We demonstrate a robust positive simultaneous correlation between the boreal summer TA SST anomalies and the EASM. Observational and model‐based studies identify an atmospheric teleconnection in which the summer TA warming can enhance convection and induce low‐level convergence in the Atlantic basin, which alters the Walker circulation and produces a sinking motion and divergence in the central Pacific. As a Rossby response to the anomalous divergence, an anomalous anticyclonic pair is generated over the western Pacific. As a result, the EASM is strengthened. Additionally, a significant lag correlation of the EASM with TA SST anomalies from the previous boreal spring is demonstrated, which implies potential applicability of the TA SST factor to the EASM prediction at seasonal time‐scales. (a) Summer 850 hPa vorticity (dotted areas; unit: 10−6 s−1) and wind (arrows; unit: m/s) regressed onto the IEASM, and (b) precipitation regressed onto the IEASM (dotted areas; unit: mm/day). The dotted areas represent the regression coefficients exceeding the 95% confidence level, the wind fields below the 95% confidence level are not shown, and the red and green rectangles in (a) represent the ranges of the selected IEASM in the two regions. (c) and (d) are similar to (a) and (b) but for the variables regressed onto the summer ITA. The orange streamlines in (c) are the summer mean flow in the lower level, while the blue shading in (d) is the JJA mean precipitation.