Analyses of the Short-Term Position Change of the West Pacific Subtropical High during Severe Precipitation in South China Based on Diabatic Heating

By using NCEP/NCAR daily reanalysis data, features of the short-term position variation of the west Pacific subtropical high (WPSH) during severe precipitation in June 2005 in South China and its relation to diabatic heating on are analyzed based on the complete vertical vorticity equation. The results show that the position variation of WPSH is associated with the diabatic heating. In comparison with the climatology, there is strong heating on the north side of WPSH and relatively weak ITCZ convection on the south. Each of westward extension of WPSH corresponds to a significantly enhanced heating to the west of WPSH. In mid-troposphere, the vertical variation of heating on the north (south) of WPSH is basically greater(less) than the climatology, which is unfavorable for the northward movement of WPSH. In the mid and late of June 2005, the vertical variation of heating over the eastern coast of the Arabian Sea and the Bay of Bengal (to the west of WPSH) is largely higher than the climatology, which is in favor of the increase of anti-cyclonic vorticity on the west of WPSH, inducing westward extension of WPSH.