Relationship between the geopotential height anomalies induced by tropical cyclones and the meridional movement of the western Pacific subtropical high

The present study employs statistical analysis to investigate the relationship between the geopotential height anomalies induced by tropical cyclones (TCs) and the meridional movement of the western Pacific subtropical high (WPSH), as well as the mechanisms through which TCs can induce such geopotential height anomalies. Results show that TCs can cause the WPSH to move northward, and the meridional motion of the WPSH ridgeline is related with the geopotential height anomalies, which is better indicated by the relative geopotential height anomalies. In the process of TCs causing the WPSH to move northward, the TCs cause abnormal horizonal warm (cold) advection and abnormal ascending (descending) motion in the region south (north) of 40°N. Since the influence of the abnormal vertical motion is weaker, the abnormal temperature tendency eventually shows a more consistent phase distribution with the abnormal horizonal temperature advection, which is favorable for the temperature to abnormally increase near 40°N. Such an abnormal increase in temperature causes the geopotential height to abnormally increase under the static equilibrium constraint, which further changes the location of the centroid of the WPSH geopotential height, and hence the location of the WPSH ridgeline changes as well.

摘要

本文采用统计分析方法, 讨论了热带气旋引起的位势高度异常与西太副高经向移动之间的关系, 并给出了可能机理. 研究表明, 热带气旋可导致西太副高向北移动, 这样的西太副高异常移动与相对位势高度异常的联系更加紧密. 其原因在于, 热带气旋在40°N附近引起了异常水平温度平流和异常垂直运动, 这对西太副高异常北移起到了重要作用. 但由于异常垂直运动的影响相对较弱, 使得异常温度倾向最终与异常水平温度平流更为一致, 导致40°N附近温度异常升高.这样温度异常升高在静力平衡约束下又导致位势高度异常升高, 最终使得西太副高的经向位置发生变化.