Analysis of Temporal and Spatial Variation of Growing Season Drought in Jiling Province Based on Standardized Precipitation Evapotranspiration Index

A standardized precipitation evapotranspiration Index (SPEI), combining the advantage of standard precipitation index (SPI) and palmer drought severity index (PDSI), is computed at different time scales (1, 3, 6 months) in Jilin Province, based on monthly precipitation and temperature data, got after preprocessing of China surface climatological data daily data set provided by National Meteorological Information Center. The temporal and spatial characteristics of drought in growing season were analyzed using linear trend analysis, Mann-Kendall trend test, Mann-Kendall abrupt test, and spatial interpolation. The results showed that from 1968 to 2017, the SPEI decreased with a rate of 0.109 10 a-1 approximately based on SPEI-6 in October, indicating that there is drying trends in Jilin Province. However, inter-annual drought fluctuates, the pattern of wet-dry-wet-dry during this period is identified, and is associated with three turning year points of 1975, 1985, and 1995. Through using SEPI-3 to analyze seasonal variation, we find that the trend of aridification in autumn is significant. The SEPI-1 decreased in growing season, from April to October, too. Monthly SPEI (SPEI-1) demonstrates that the total number of droughts was the highest in October, September takes second place, nevertheless, mild drought in the two months is more than others. July is the month with the most moderate drought, and far more than in any other month. Severe drought in June happens more frequently, and the situation is like the moderate drought in July. Extreme drought is relatively less, about 12 times every month in these 50 years. Spatial distribution of drought in the district was heterogeneous and complexity. Totally, the western region was the most seriously affected area, with the highest drought frequency, especially along the southwest administrative line and separate region of the southeast. SPEI of six-month scale in October shows that extreme drought infrequently, only in the southeast and southwest of the individual areas; severe drought mainly distributes in the western region, especially Songyuan, Qianan, Changling, Siping and so on; Western such as Daan, Baicheng, Tongyu, North Central Changchun, Jiaohe, Wangqing etc., is where moderate drought happen more frequently; most of the area has experienced mild drought, and it happened more frequently along the southwest provincial boundaries. The results of this study may provide a scientific basis for early drought prediction and risk management of water resources and agricultural production in Jilin Province.