青藏高原东部大气热源与高原涡的关系

Relationship between Atmospheric Heat Source and the Plateau Vortex in the Eastern Tibetan Plateau

基于ERA5再分析资料和高原低涡统计数据集,采用倒算法计算了1991-2017年青藏高原东部的大气热源,分析了大气热源与高原涡生成频数、移出频数及初生性质的关系.结果表明:①1991-2017年,7月份高原东部大气热源平均强度为172 W/m^(2),振荡周期为5~7年,空间分布具有明显的局地差异,东南部大气热源高于东北部.随纬度增加,大气热源明显减弱,高原南坡是大气热源最强的区域.②大气热源偏强有利于高原涡的生成及移出,强年高原涡生成频数及移出频数均多于弱年.③分析大气热源强弱年环流场差异,证明强年环流形势有利于高原涡的生成及移出,具体影响机制为:强年南坡大气热源中心气柱上升运动强烈,整层大气呈现强烈的上升运动,低层辐合,高层辐散,南亚高压脊线东伸脊点位于120°E,高层西风急流大值区位于高原东部,低层存在利于高原涡移出的横槽.

Based on the ERA5 reanalysis data and the Plateau Vortex statistical data set,the inverse algorithm was used to calculate the atmospheric heat source in the eastern part of the Tibetan Plateau from 1991 to 2017,and the relationship between the atmospheric heat source and the Plateau Vortex generation frequency with removal frequency and incipient nature was analyzed.The results show that:①From 1991 to 2017,in July,the average atmospheric heat source in the eastern part of the plateau was 172 W/m^(2),the oscillation period was 5-7 years,and the spatial distribution had obvious regional differences.The atmospheric heat source in the southeast was higher than that in the northeast.From south to north,the atmospheric heat source was obviously weakened with the increase of latitude,and the southern slope of the plateau was the area with the strongest atmospheric heat source.②There is a positive correlation between the strong atmospheric heat source and the generation frequency with removal frequency of the Plateau Vortex.The generation frequency and removal frequency of the Plateau Vortex in strong years are more than those in weak years.③Analysis of the difference in the circulation field between the strong and weak years of the atmospheric heat source proved that the strong annual circulation situation is conducive to the formation and removal of the Plateau Vortex,and explained its influence mechanism:in strong year,the upward movement of the air column in the center of the atmospheric heat source on the southern slope is strong,the whole atmosphere is strongly move upward,the convergence of the lower layers and the divergence of the upper layers,the eastward extension of the South Asian High Ridge Line is located at 120°E,the high-level westerly jet high-value area is located in the eastern part of the plateau,and there are transverse troughs in the lower layers that are conducive to the migration of the Plateau Vortex.