1961—2019年长江中下游区域性干旱过程及其变化

客观识别区域性干旱过程，评估其强度是开展精准监测、评估干旱影响业务的基础。基于长江中下游地区502个国家级气象站1961—2019年逐日气温、降水资料以及1971—2019年干旱受灾面积，运用气象干旱综合指数（MCI）及区域性干旱过程识别方法，识别出长江中下游地区126次区域性干旱过程，干旱过程的次数随着持续天数增多呈明显减少趋势，决定系数达0.89。1961—2019年长江中下游地区共发生6次特强区域性干旱过程、19次强区域性干旱过程、38次较强区域性干旱过程，其余63次为一般区域性干旱过程，区域性干旱过程的持续天数、平均强度、平均影响面积以及综合强度指数的变化趋势形态各异。长江中下游地区年干旱日数总体呈现“北部多于南部、平原多于山区”的分布特征，且总体呈现“西北部增多、东南部减少”的变化趋势，干旱日数与干旱受灾面积变化趋势较为一致，相关系数达0.66。由典型区域性干旱过程监测评估可知，干旱综合强度指数与干旱站数存在明显的正相关，干旱综合强度指数越强，各等级干旱站数越多；各地干旱日数的多少与干旱受灾面积的大小也较为一致，干旱日数越多的地区，干旱受灾面积越大。总体来看，区域性干旱过程识别方法及评估结果与干旱灾情较为吻合，能较好地识别出区域性干旱过程，并可从持续天数、平均强度、平均影响面积以及干旱综合强度等多角度对干旱过程进行监测评估。 

Regional drought process and its variation characteristics in the middle-lower reaches of the Yangtze River from 1961 to 2019

Objectively identifying regional drought processes and assessing their intensity is the operational basis for conducting accurate and detailed monitoring and assessment of drought impacts. Based on daily temperature and precipitation data collected at 502 national meteorological stations from 1961 to 2019 and the historical drought disaster information from 1971 to 2019 in the middle-lower reaches of the Yangtze River, 126 regional drought processes in the middle-lower reaches of the Yangtze River were identified using the meteorological drought composite index (MCI) and regional drought process identification method. The number of drought processes decreases obviously with the increase of duration days, and the determination coefficient reaches 0.89. From 1961 to 2019, there were 6 extremely strong regional drought processes, 19 strong regional drought processes and 38 sub strong regional drought processes in the middle-lower reaches of the Yangtze River, and the remaining 63 were general regional drought processes. The variation trend of duration days, average intensity, average affected area and comprehensive intensity index of regional drought processes present different forms. The distribution of annual drought days in the middle-lower reaches of the Yangtze River is generally "more in the north than in the south, more in the plain than in the mountainous area", and the trend shows a pattern of "increasing in the northwest and decreasing in the southeast". The variation trend of drought days is consistent with that of drought affected area, and the correlation coefficient reaches 0.66. According to the monitoring and assessment of typical regional drought processes, there is an obvious positive correlation between the comprehensive drought intensity index and the number of stations that experienced drought. The stronger the comprehensive drought intensity index, the larger the number of stations experiencing various levels of drought. The number of drought days in different regions is consistent with the size of drought disaster area. The more drought days, the greater the drought disaster area. In general, results of identification and assessment of regional drought processes are consistent with drought disaster information. The method of identification and assessment of regional drought processes can well identify the regional drought process, and monitor and assessment the drought process from the perspectives of duration days, average intensity, average affected area and comprehensive drought intensity.