基于SPEI-3的云南省干湿变化时空特征分析

Spatial-Temporal Characteristics Analysis of Dry and Wet Changes in Yunnan Province, China Based on SPEI-3 Index

摘要: 为探明滇近62 a的干湿变化特征，本文利用Penman-Monteith法计算了1958~2019年滇的潜在蒸散发量(PET)，并计算了以3个月为步长的标准化降水蒸散指数(SPEI)。利用Manner-Kendall突变检验、Morlet连续复小波变换(CCWT)分析了1958~2019年滇均值SPEI-3的变化趋势、突变点及干湿变化周期，利用经验正交函数(EOF)基于23个站点的SPEI-3指数对滇干湿变化的时空特征进行提取。研究结果显示，①滇西北、东北降水增多，其他地区降水均呈不同程度减少。滇南部降水逐年减少、蒸发强烈、滇南部变干趋势极显著。滇南部是干旱发生的重灾区。② 滇均值SPEI-3呈显著下降趋势，全省变干趋势显著，变点发生在2007年。滇干湿变化周期以26、3年为尺度的变化周期最为显著，以26年尺度周期震荡最强，为滇干湿变化的第一主周期。在26、3年特征时间尺度上，滇干湿变化的平均周期分别为49、9年左右。③ 滇干湿变化的空间场主要有6种表现类型，在1958~2019年间有19 a全滇变湿、17 a全滇变干、滇东南变湿西北变干有6 a、有13 a滇东南变干西北变湿。在1958~2019年滇干湿变化以变干为主，其中西南、东南部的变干趋势极显著。滇SPEI-3指数的空间变化与滇农作物旱灾受灾面积变化趋势较一致，说明SPEI-3计算结果指示性强，可用于预测滇干湿变化。

Abstract: In order to explore the characteristics of dry and wet changes in Yunnan Province in recent 62 years. In this paper, we calculated the potential evapotranspiration (PET) of Yunnan Province from 1958 to 2019 by Penman-Monteith method, and on this basis, calculated the SPEI drought index at a pace of 3 months. The author has used Manner-Kendall mutation test and Morlet complex continuous wavelet transform (CCWT) to analyze the variation trend, mutation point and dry-wet change period of mean SPEI-3 index in Yunnan Province from 1958 to 2019, and extracted the spatial-temporal characteristics of dry-wet change in Yunnan Province by empirical orthogonal function (EOF) decomposition method. The result showed that: ① The precipitation increased in the northwest and northeast of Yunnan Province, while in other areas of Yunnan Province, the precipitation decreased to varying degrees. There is little precipitation and intense evaporation in the south, and the drying trend in the south is very significant. The south is the worst-hit area of drought. ② The mean SPEI-3 index showed a significant downward trend, and the trend of drying was obvious throughout the country. The change time occurred in 2007. The cycle of dry and wet change in the study area has a significant change rule on the scale of 26 and 3 years, and the periodic oscillation on the scale of 26 years was the strongest, which was the first main cycle of dry and wet change in Yunnan Province. On the characteristic time scale of 26 years, the average period of dry and wet change in the study area was about 49 years. On the 3 years characteristic time scale, the average cycle of dry and wet change in the study area was about 9 years. ③ The spatial field of wet and dry variation has 6 types. In 1958~2019, there were 19 years in which the whole region got wet and there were 17 years in which the whole region got dry. Meanwhile, it took 6 years for the southeast to get wet and the northwest to get dry, and 13 years for the southeast to get dry and the northwest to get wet. During the period from 1958 to 2019, the dryness and wetness in Yunnan Province were the main change, and the dryness trend in the southwest and southeast was extremely significant. The spatial variation of SPEI-3 index was consistent with the area affected by drought in Yunnan Province, which indicated that the calculation results of SPEI-3 were highly indicative and could be used to predict dry-wet changes.