青藏高原近地层及北侧气压系统的季节性振荡变化

Seasonal variations of the pressure systems in surface layer and northern regions of the Tibetan Plateau

基于ERA-Interim逐日4次600 h Pa位势高度再分析资料,以及青藏高原和周边地区75个气象站日平均温度、降水和相对湿度资料,对高原近地层及北侧气压系统的季节性振荡变化进行了分析.结果表明:高原近地层及北侧气压系统强度在围绕中心点顺时针运动时不断加强,逆时针运动时不断减弱.两气压系统呈明显的跷跷板式变化,在600 h Pa上表现为高度场空间结构沿经向上的调整;低高压差负值的开始和结束时间与高原季风起讫时间吻合.高原夏季降水的起讫不仅与高原及北侧气压系统结构密切相关,而且与高原东南或南部水汽输送条件息息相关.

Based on the reanalyzed data of ERA-Interim daily 600 hPa geopotential height and the daily mean temperature,precipitation and humidity data from 75 meteorological stations over the Tibetan Plateau and its adjacent regions,seasonal variations of pressure systems in surface layer and northern regions over the Tibetan Plateau were analyzed. The results indicated that the intensities of pressure systems in surface layer and northern regions will constantly strengthen when the system rotates clockw ise surround a center and will constantly weaken when the system rotates anti-clockw ise surround a center. At 600 hPa,pressure system strengthens in surface layer but weakens in northern Tibetan Plateau. The height gradient points from north to south as the plateau summer monsoon starting and points from south to north as the plateau summer monsoon ending. The starting and ending times of plateau summer precipitation are not only closely related to pressure systems in surface layer over the plateau and its northern regions,but also closely related to water vapor transport in the southeast and south Tibetan Plateau.