基于2020年云南125个站逐日MCI指数和区域性气象干旱过程监测评估标准， 分析了4 -6月区域性气象干旱的时空分布特征， 并从高低层大气环流分布研究了其发生的成因。研究表明： （1）2020年4 -6月发生了两次区域性气象干旱过程， 一次是4月1 -25日云南西南部有重度以上强度的气象干旱， 另一次是5月9日至6月30日全省性、 持续时间长的严重气象干旱。（2）2020年4月1 -25日500 hP高度场在乌拉尔山和东亚东部为低压槽区， 巴尔喀什湖至贝加尔湖一带为高压脊区， 在中高纬度形成“负-正-负”波列， 有利于西伯利亚冷空气堆积南下影响云南， 但低纬度地区为带状正异常高度场控制， 云南区域700 hPa风场为南风异常， 所以冷空气主要影响云南东部。低纬度地区阿拉伯海-孟加拉湾-南中国海高度场偏高， 不利于西南暖湿气流向云南输送， 云南区域70%的水汽输送轨迹来自西风带。因此云南西部降水偏少、 气温偏高， 发生了区域性气象干旱过程。（3）5月9日至6月30日南亚高压季节性转换偏晚， 孟加拉湾区域季风环流建立偏迟。季风建立前， 云南区域水汽输送轨迹均来自西风带， 比湿以负距平为主。季风建立后， 云南区域水汽输送轨迹97%来自印度洋， 比湿以正距平为主， 但500 hPa中高纬度环流分布不利于冷空气南下影响云南， 同时云南区域为10 gpm以上正距平的高度场控制， 下沉运动加强， 水汽输送与辐合上升运动对应关系不好， 所以发生了全省大范围的气象干旱。

Based on the daily MCI （Meteorological Drought Composite Index） of 125 stations in Yunnan province from April to June 2020， and the monitoring standard of regional drought process， the spatial-temporal distribution characteristics are analyzed， and the circulation causes of meteorological drought are also investigated.The results demonstrate that： （1） Two meteorological drought processes occurred from April to June 2020， one is a severe drought in southwestern area of Yunnan from April 1 to 25， and another was from May 9 to June 30 which is a severe drought with a long duration in the whole province.（2） From April 1 to 25 in 2020， the distribution of Mid-high latitude 500 hPa height field are two troughs and one ridge， a trough of low pressure in the Ural Mountains and eastern East Asia， and a ridge of high pressure in the area from Lake Balkhash to Lake Baikal， forming a "negative-position-negative" wave train which is conducive the cold air to the southward and impact of Yunnan.The low latitudes are controlled by a zonal positive abnormal height field， and there is south wind anomaly of 700 hPa in Yunnan， so the cold air mainly affects eastern of Yunnan.The Arabian-Sea-Bay of Bengal-South China Sea of 500 hPa height field is positive anomaly， which is not conducive to the transport of southwest warm and humid air to Yunnan.70% of the water vapor transport tracks to Yunnan come from the westerlies， so the regional meteorological drought process occurs in western Yunnan with less precipitation and higher temperature.（3） From May 9 to June 30， the seasonal transition of South Asian High is later than normal， and the establishment of the regional monsoon circulation in the Bay of Bengal is late also.Before the establishment of monsoon， all of the water vapor transport tracks to Yunnan region come from the westerly belt， and the specific humidity is mainly negative anomaly.After the establishment of the monsoon， 97% of the water vapor transport tracks to Yunnan come from the Indian Ocean， and the specific humidity was mainly positive anomaly.However， the circulation distribution in the middle and high latitudes of 500 hPa is not conducive the cold air to the southward and impact Yunnan.Meanwhile， the distribution of low latitude 500 hPa is positive anomaly， and the subsidence movement is strengthening， the correspondence between water vapor transport and the convergence rising motion was not good， so a sever large-scale meteorological drought occurred in Yunnan province.