Relationship Between The Spatial And Temporal Characteristics Of The Thermal Forcing Over The Tibetan Plateau And The Changes Of South Asia High During Spring And Summer

Based on the NCEP/NCAR reanalysis daily data from 1983 to 2012, using the Lanczos filter, Morlet wavelet analysis method and other statistical methods, the climatically averaged characteristics of circulation field of South-Asian high (SAH) moves on the Tibetan Plateau(TP) from May to Jun and its relation to the diabatic heating over the adjacent areas of TP, the features of low frequency oscillation between the vertically integrated atmospheric heat source(< Q1,>) over the TP and longitudinal oscillation of SAH and relationship between them in summer are investigated. The results showed that:(1) The results showed that SAH moves northwest from the northern Indo-China Peninsula (ICP) and completely moves on TP thirty-third pentad, which is consistent with the time when south of TP becomes the main heat source center in southern Asia, and<Q1> in the south of TP increases more faster than that in the south bay of Bengal (BOB) to the ICP, which may be one of the reasons SAH shifts on the TP. And analysis of the relationship between the heating fields and streamline fields by using of the simplified complete vertical vorticity equation, it’s found that the relative vorticity advection and the geostrophic vorticity advection are conducive to SAH westward movement,the vertical change of diabatic heating is in favor of SAH northward movement,three together make the SAH moving to the northwest to the TP.(2)The main frequency period of<Q1> over the eastern TP in summer is quasi-biweekly, which is as the same as the longitudinal oscillation of SAH, the secondary frequency period is 30-60d and quasi-weekly respectively. Standing wave showed by<Q1> 10～20d low frequency components over the TP in summer and their meridional and zonal propagation characteristics are not significant. The eastern plateau is relatively large value areas of<Q1> 10-20d variance contribution rate, which is larger than the area over Changjiang-Huaihe river valley.(3)At the peak phase of 10-20d low-frequency<Q1> of the eastern plateau in summer, 10 20d low-frequency cyclone over the TP and anticyclone over the western TP lead to the SAH moving westward, which shows Iran high mode. At the valley phase, the low-frequency circulation situation is completely opposite. TP is controlled by the low frequency anticyclone and western plateau is controlled by the low-frequency cyclone, resulting in the SAH eastward and presenting the Tibetan high mode. Wind field variations caused by the changes of warm center over the TP, which led by plateau thermal field anomalies, can explain SAH longitudinal oscillation.