2017年5—7月内蒙古中东部地区气象干旱及环流特征分析

Analysis of the meteorological-drought in mid-eastern Inner Mongolia from May to July in 2017 and the characteristic of atmosphere circulation

利用内蒙古自治区116个气象站1981—2017年5—7月逐日降水量、平均气温观测资料和逐日综合气象干旱指数(MCI)监测值。美国NCEP/NCAR 1981—2017年5—7月平均再分析资料等,分析了2017年5—7月内蒙古中东部地区发生的大范围持续气象干旱的气候背景、季风和大气环流特点等,得出:(1)2017年5—7月内蒙古中东部地区降水量异常偏少,气温异常偏高,且持续时间长,影响严重,是近36a来少有的。(2)北极涛动指数维持正位相,冷空气活动势力弱,欧亚地区盛行纬向环流;青藏高原高度场持续偏高,印缅槽持续偏弱;太平洋副热带高压强度偏强、面积偏大、西伸脊点偏西;南海夏季风较常年偏弱,我国主雨带位置偏南。大气环流的异常分布和共同影响,使得内蒙古中东部地区长时段处于高温的环流影响下,没有系统性的西南水汽输送,出现了大范围持续异常高温少雨天气,导致内蒙古中东部地区持续重旱。

The characteristics of climate background, monsoon and atmosphere circulation, which lead the extensive and persistent meteorological-drought occurred in the mid-eastern Inner Mongolia, was analyzed by using daily precipitation, daily average temperature and daily meteorological drought index （MCI） data of 116 national weather stations, and NCEP/NCAR reanalysis data in May to July from 1981 to 2017. Some signifcant results were showed （1）The precipitation and temperature from May to July in 2017 in mid-eastern of inner Mongolia are obviously fewer and higher than average, and its long duration and serious infuence were scarce in last 36 years. （2）Arctic Oscillation （AO） kept to positive phase. Cold air was not active. Zonal circulation was prevailling over Eurasia. Qinghai-Tibet Plateau geopotential height continued higher than average. India-Burma Trough continued lower. Western Pacifc Subtropical High continued more intense, larger and west than average in intensity, area and Western Ridge Point. South China Sea summer monsoon was weaker and main rain-band was south than average. Infected by the abnormal atmosphere circulation, mid-eastern of Inner Mongolia was controlled by high temperature circulation, no systematic south-western water vapor transport, and extensive and persistent hot and dry weather took place, which caused serious drought in mid-eastern Inner Mongolia.