基于SPEI指数的近58 a甘肃省干旱特征分析

利用甘肃省19个气象站点1960—2018年逐月平均降水量、气温等数据,应用标准化降水蒸散量指数(Standardized Preapitation Evapotranspiration Index,SPEI)、Penman-Monteith模型、小波分析等方法分析了甘肃省近58 a不同时间尺度干旱事件的时空演变特征。结果表明:月尺度干旱频率3月最高,2月最低;季尺度上秋季干旱最严重,春季次之;冬季干旱化趋势最慢,春季最快。近58 a甘肃省SPEI指数呈下降趋势,年尺度SPEI指数存在8 a、12 a、26 a的周期。干旱发生频率在年尺度和月尺度上的分布较为一致,河西走廊东段与甘南州地区频率较低,酒泉北部地区与甘肃省东、中部地区频率较高;季尺度上,春季兰州与武威南部地区频率较高,庆阳地区频率最低;夏季为白银与武威北部地区频率最高,张掖中部地区、白银北部地区以及临夏、庆阳、平凉地区最低;秋季频率最高的地区为兰州东部、定西东北部以及嘉峪关地区,最低的地区在酒泉、张掖、武威北部及平凉中部地区;冬季高值区在平凉,低值区在武威与甘南。干旱发生强度最高的地区为张掖,其次为酒泉、庆阳及白银等地区,最低的区域位于甘肃西南地区。酒泉、嘉峪关等地区干旱化程度逐年加剧;甘肃东南地区干旱速率较西北地区慢;中西部地区干旱化速率最慢,且甘南北部与武威西南部地区有湿润化趋势。

Analysis of drought characteristics in Gansu Province in recent 58 years based on SPEI index

By using the monthly average precipitation and temperature data of 19 meteorological stations in Gansu Province from 1960 to 2018, the spatio-temporal evolution characteristics of drought events at different time scales over the past 58 years in Gansu Province were analyzed by means of Standardized Precipitation Evapotranspiration Index(SPEI), penman-monteith model and wavelet analysis. The results show that the monthly drought frequency was the highest in March and the lowest in February. The drought was most serious in autumn, followed by spring. The trend of drought is the slowest in winter and the fastest in spring. In recent 58 years, the SPEI index in Gansu Province has been on a downward trend, and the annual scale SPEI index has existed for 8, 12 and 26 years. The distribution of drought frequency on annual scale and monthly scale is consistent. The frequency in the eastern part of Hexi corridor is lower than that in Gannan prefecture, and higher in the northern part of Jiuquan and the eastern and central parts of Gansu Province. On the seasonal scale, the frequency is the higher in the south of Lanzhou and Wuwei, and the lowest in Qingyang in spring. In summer, the frequency is highest in Baiyin and northern Wuwei, and lowest in central Zhangye, northern Baiyin and Linxia, Qingyang and Pingliang regions. The highest frequency in autumn is in the east of Lanzhou, the northeast of Dingxi and Jiayuguan, and the lowest is in the north of Jiuquan, Zhangye and Wuwei and the middle of Pingliang. Winter high value area in Pingliang, low value area in Wuwei and Gannan. The drought intensity was highest in Zhangye, followed by Jiuquan, Qingyang and Baiyin, and lowest in southwest Gansu. The degree of drought in Jiuquan and Jiayuguan is increasing year by year. The drought rate in the southeast of Gansu is slower than that in the northwest. The rate of drought is the slowest in the central and western regions, and there is a wetting trend in the northern part of Gannan and the southwestern part of Wuwei.