南亚高压上下高原时间及其与高原季风建立早晚的关系

本文利用1948—2013年NCEP/NCAR逐日再分析资料,定义了南亚高压动态特征指数,讨论了南亚高压上下高原的时间以及与高原季风建立早晚的关系。研究表明,南亚高压北界位置在4月初开始北移,5月迅速北抬,最北可达到55°N,9月开始南撤,西伸脊点在5—10月移动较稳定,5—7月向西移动到青藏高原上空,8—10月向东移动撤离高原,11月—次年4月东西摆动剧烈。南亚高压初上高原大致为6月第3候(33候),而撤离约为10月第4候(58候)。南亚高压移上高原的时间较高原夏季风建立晚73 d左右。南亚高压撤离高原时间较高原冬季风建立约早5 d。高原夏季风的建立和南亚高压初上高原是青藏高原热力作用在不同阶段的结果,反映在了高原的高低层上。

Establishment or retreatment average date of South Asian High over the Tibetan Plateau and its relation with the Tibetan Plateau monsoon onset

By using the NCEP/NCAR daily reanalysis data from 1948 to 2013, the establishment or retreatment average date of South Asian High (SAH) over the Tibetan Plateau and its relation with the Tibetan Plateau summer monsoon onset was analyzed. Results show that the SAH moved northward at the beginning of April, jumpped northward abruptly in May, reached to the most northern position of 55°N in August, and then withdrew southward in September. SAH moved westerly stablely from May to October, and swang drastically from November to the next April. It is concluded that the first establishment average date of SAH over the Tibetan Plateau is on the 33rd pentad of June,and the climate-mean SAH moving out over the Tibetan Plateau is on the 58th pentad of October. The moving date of SAH on the Tibetan Plateau is 73 days later than that of the Plateau summer monsoon onset, and the retreatment date over the Tibetan Plateau is 5 days earlier than that of the plateau winter monsoon onset. The relation between establishment of SAH over the Tibetan Plateau and Tibetan Plateau summer monsoon onset can be explained the thermal effects of the Tibetan Plateau at different stages, which depend on different heights.