A Numerical Study on the Anomalies of the South Asian High and the Subtropical Western Pacific High

Abstract

A numerical study on the relationship between the interannual longitudinal oscillation of the South Asian High (SAH) and the subtropical western Pacific high (SWPH) and the heat source anomalies during boreal summer has been conducted by using a high-resolution regional climate model IPRC-RegCM. The results show that the anomalous heating (cooling) over the Yellow River and Huaihe River valley may play an important role in the longitudinal oscillation of the SAH and the SWPH in summer. Further study suggests that the heat source (sink) strengthens (weakens) the ascending motion of the air over the Yellow River and Huaihe River valley, which reinforces (reduces) the high-level divergence. Consequently, the intensity of the SAH increases (decreases) and the ridge of the SAH extends further eastward (withdraws westward). In addition, due to the anomalous northerly in upper (middle) troposphere the abnormal sinking (rising) motion of the air occurs above the sea in middle and low latitudes, which is accompanied by adiabatic heating (cooling). As a result, the deep and warm SWPH is strengthened (weakened) and extends further westward (withdraws eastward).