Impact of winter SST anomaly in tropical Eastern Pacific on following summer tropical cyclone precipitation in China

Abstract

AbstractThis study reveals a significant effect of the winter sea surface temperature (SST) anomaly (SSTA) in the tropical Eastern Pacific (TEP) on the following summer tropical cyclone precipitation (TCP) in mainland China. During the period 1979–2015, the positive winter TEP SSTA forces a SST zonal tripole pattern anomaly, which is positive SSTA in the tropical Indian Ocean (TIO), negative SSTA in the tropical Western Pacific (TWP), and positive SSTA in the TEP. This SSTA pattern triggers two simultaneous zonal circulation anomalies. One exhibits lower‐level convergent winds, mid‐tropospheric ascendant flows and upper‐level divergent winds over the Western TIO, and reversed situations over the TWP, producing anomalous lower‐level easterlies and upper‐level westerlies between the TIO and TWP. The other shows lower‐level convergence, mid‐tropospheric ascent, upper‐level divergence over the TEP, and reversed situations over the TWP, which create lower‐level westerlies and upper‐level easterlies between the TWP and TEP. The two circulation anomalies further warm the TEP (Western TIO) by driving ambient warm water toward this region and cool the TWP by inducing local upwelling, which facilitates the persistence of the anomalies until the summer. Consequently, the lower‐level negative vorticity, strong vertical wind shear and the lower‐level anticyclone anomalies over most of the Western North Pacific (WNP) are accompanied with anomalous mid‐tropospheric westerlies over the coastal regions in mainland China, suppressing TC genesis and movement towards mainland China so as to decrease the summer TCP in mainland China. These results provide an important implication that the winter TEP SSTA is a potential indicator for seasonal prediction of the WNP TC activity and the TCP in mainland China.