青藏高原天气系统对昆仑山北坡一次罕见暴雨过程影响分析

Analysis of the Influence of the Qinghai-Xizang PlateauWeather System on a Rare Rainstorm Process on the Northern Slope of Kunlun Mountain

利用南疆塔里木盆地加密自动站数据、常规地面观测和高空探测资料、NCEP 1°×1°再分析资料和欧洲中心ECMWF模式预报初始场资料(空间分辨率0.125°×0.125°),针对2019年6月24-26日发生在昆仑山北坡罕见的暴雨过程,分析了南亚高压、高原低涡和切变线等高原天气系统对昆仑山北坡暴雨的影响。结果表明,暴雨出现在100 hPa南亚高压双体型转为青藏高压单体型的大尺度环流下,500 hPa中低纬呈“两高夹一低”经向环流,西太平洋副热带高压(简称西太副高)不断西伸,外围偏南风盛行,伊朗高压东进加强,两高之间的高原切变线和低涡维持。500 hPa偏西和偏南两条水汽输送路径中,偏南水汽输送持续更长,偏南气流将孟加拉湾水汽输送至青藏高原和昆仑山脉,水汽辐合明显,暴雨出现在中层水汽输送和辐合的叠加区,水汽源地来源于孟加拉湾、里海和咸海,孟加拉湾水汽贡献更大。高空偏南暖湿气流沿低层“冷垫”爬升,有利于动力抬升并加剧垂直方向的冷暖交绥。

Using the encrypted automatic station data,conventional ground observation and high-altitude sounding data,NCEP 1°×1°reanalysis data and ECMWF model prediction initial field data(spatial resolution 0.125°×0.125°)in the Tarim Basin of southern Xinjiang,aiming at a rare torrential rain process occurred on the northern slope of Kunlun Mountain from 24 to 26 June,2019.The influence of plateau weather systems such as South Asia High,plateau vortex and shear line on the northern slope of Kunlun Mountain was analyzed.The results showed that the heavy rain occurred under the large-scale circulation of the 100 hPa South Asian high doublebody type converted to the Qinghai-Xizang high pressure haplotype.The 500 hPa mid-low latitudes showed"two highs sandwiched one low"meridian circulation,and the West Pacific Subtropical High continued to extend westward.The southerly wind prevails in the periphery,the high pressure of Iran strengthens eastward,and the plateau shear line and low vortex between the two highs are maintained.In the two water vapor transport paths of 500 hPa westward and southward,the southerly water vapor transport lasts longer.The southerly airstream transports water vapor from the Bay of Bengal to the Qinghai-Xizang Plateau and the Kunlun Mountains.Convergence of water vapor is obvious.Heavy rain occurs in the middle-level water vapor transport and convergence In the superimposed area,the water vapor source comes from the Bay of Bengal,the Caspian Sea and the Aral Sea,and the water vapor in the Bay of Bengal contributes more.The high-altitude southerly warm and humid airflow climbs along the low-level"cold cushion",It is conducive to power uplift and aggravates the warm and cold changes in the vertical direction.