气象干旱过程识别及致灾因子特征分析

为科学识别气象干旱及其发生、发展过程，并探究其致灾因子变化特征，通过1981—2020年海西州8个气象站点逐日气象干旱综合指数（Meteorological drought composite index，MCI）描述历年干旱事件，识别干旱过程个数、入旱出旱时间，分析干旱过程强度、干旱过程降水量等。结果表明：1981—2020年，海西州共识别干旱过程192个，干旱开始时间介于5月18日—6月20日之间，结束时间介于7月4日—8月8日之间，历时时长40~63 d；各等级干旱日数变化趋势不一，茫崖、乌兰县干旱日数变化呈增加趋势，变化倾向率分别为2.0 d·（10a）^-1，1.0 d·（10a）^-1，其余站点呈减小趋势，变化倾向率介于-4.0～-1.0 d·（10a）^-1。不同干旱等级的干旱日数大体呈中部少，西部多的态势，西南地区干旱最为严重；时间序列上，轻、中、重、特旱日数和年最长连续干旱日数呈减少趋势；年最长连续干旱日数均值为16 d，最大值为65 d （1995年）；茫崖干旱过程强度最高，天峻和都兰相对较低。

Recognitions of Meteorological Drought Process and Charactistic Analysis on Disaster Causing Factors

In order to scientifically identify meteorological drought process and explore the changing characteristics of disaster causing factors, the daily meteorological drought comprehensive index (MCI) of eight meteorological stations from 1981 to 2020 in Haixi Prefecture was used to describe the drought events over the years, identify the number of drought processes and the entry and exit time of drought, and also analyze the intensity and precipitation of drought process. The results showed that, a total of 192 drought processes were identified in Haixi Prefecture from 1981 to 2020. The drought started from May 18 to June 20, and ended from July 4 to August 8, lasting for 40~63 days. The change trend of drought days in different grades was different. It showed an increasing trend in Mangya and Wulan counties, and the changing tendency rates were 2.0 d·(10a)^-1 and 1.0 d·(10a)^-1, respectively. While it showed a decreasing trend in the other stations, and the changing tendency rate was between -4.0 d·(10a)^-1and -1.0 d·(10a)^-1. The drought days of different drought grades were generally fewer in the middle and more in the west. Moreover, the drought in southwest is the most serious. In the time series, the light, medium, heavy, special drought days and the longest continuous drought days showed a decreasing trend. The maximum mean number of consecutive drought was 16 days with a maximum of 65 days in 1995. The intensity of drought process was the highest in Mangya and comparatively lower in Tianjun and Dulan.