新疆哈密大降水的大气环流特征分型

利用1951~2012年新疆哈密市的观测资料和NCEP再分析资料,对造成哈密市大降水(12.0 mm)的大气环流特征进行合成分析。结果发现造成哈密站大降水的大气环流分为4种类型:横槽型、低涡型、低槽(ω)型和不稳定小槽型。其中出现暴雨以上降水(24 h降水量24.0 mm)的个例集中在低槽(ω)型;横槽型个例的降水量在13.0~22.0 mm之间;低涡型个例的降水量分布相对均匀,在15.0~20.0 mm之间;不稳定小槽型个例的降水量偏少,全部在18.0 mm以下。4种类型的大气环流特征主要在对流层中高层差异明显。横槽型中低纬度环流平直,其横槽的北部是西北气流,南亚高压是青藏高压西部型;低涡型的中低纬度,在孟加拉湾有低槽,低槽的北部有低涡存在,低涡西面的脊偏强,其南亚高压是青藏高压东部型;低槽(ω)型东部的脊偏强,呈西北东南向,南亚高压是伊朗高压型;不稳定小槽型的南亚高压为伊朗高原到青藏高原东部的带状,500 hPa位势高度场上,85°E以西是平直的偏西气流,新疆东部地区有一小的短波槽。

Atmospheric Circulation Classification of Large Precipitation in Hami of Xinjiang

Based on observational data of Hami （eastern of Xinjiang）and NCEP reanalysis data,the atmospheric circulation features which could cause large precipitation （greater than 12.0 mm）in Hami were analyzed.Results show that there were four kinds of syn-optic patterns which could cause large precipitation in Hami,including the transverse -trough-type,low-vorticity-type,low-trough-type（orω-type）and unstable-small-trough-type.The cases of torrential rains （24 hours rainfall more than 24.0 mm） were mainly concentrated in the low-trough-type （orω-type）,and the precipitation of the cases for transverse-trough-type was between 13.0-22.0 mm,and it was between 15.0-20.0 mm for the cases of low-vorticity-type,while it was less than 18.0 mm for cases of unstable-small-trough-type.Four types’atmospheric circulation characteristics were significantly different mainly in middle and upper troposphere.The circulation was straight in the middle and low level for transverse-trough-type,the north of the transverse trough was northwest airflow,and the south Asia high pressure was lying over the west of Qinghai-Tibet Plateau.There was a trough over Bay of Bengal and a low vorticity in the north of the trough,the ridge in the west of low vorticity was strong,and the south Asian high was lying over the eastern of the Qinghai-Tibet Plateau.The ridge in east of the trough was stranger and lay northwest to southeast in the cases of low-trough-type （or ω-type）,and the south Asian high was the Iran-High-type.As to unstable -small-trough-type,the south Asian high presented a band from Iranian plateau to the eastern Tibetan Plateau,and a straight westerly flow was over the west of 85°E,while a small shortwave trough lay over the eastern region of Xinjiang.