基于SPEI和SPI指数的青海省东部农业区春夏气象干旱特征的评估

青海省东部农业区是青海省重要的粮食生产基地,春夏干旱直接影响着该区农业的有序发展。论文选取青海省东部农业区13个气象站点1961-2014年平均月降水和气温数据,采用泰森多边形法、SPEI和SPI指数、R/S分析等方法对比评估了该区的春夏气象干旱演变特征。研究表明：1）近54 a SPEI和SPI指数显示青海省东部农业区干旱年际变化在2000年代前基本一致,2000年代后变化趋势发生变化;SPEI指数显示2000年代后春夏旱逐渐加重,SPI指数显示2000年代后春旱逐渐缓解该区干旱,气温是导致两者产生差异的主要原因。2）该区干旱面积覆盖率与干旱年际变化规律保持一致,两种指数主要在1990年代中期前后有所不同,1990年代中期后SPEI指数显示的春夏干旱覆盖面积要比SPI指数显示的广。3）SPEI和SPI指数在2000年代后春夏干旱频率呈相反趋势,SPEI指数显示的2000年代为干旱高频期,SPI指数为干旱低频期;两种指数均显示春旱高频区由西部转向东部地区,夏旱高频区由西北转向东南地区。4）根据干旱周期及R/S分析法,未来4~6 a该区春旱加重,北部地区为春旱高发区;未来18~22 a夏旱也有所加重,西部和东部地区为夏旱高发区。5）通过对比分析发现,SPEI指数在该区的适用性较好,能为该区干旱监测提供较为科学的理论依据。

Assessment of Spring and Summer Meteorological Droughts Based on SPEI and SPI in Eastern Agricultural Region of Qinghai Province

Eastern agricultural region of Qinghai Province is an important grain production base. Spring and summer droughts directly influence the orderly development of agriculture in this region. The average monthly precipitation and temperature data during 1961-2014 at 13 meteorological stations in eastern agricultural region of Qinghai Province were acquired. The trends of spring and summer meteorological droughts were evaluated with methods of SPEI index, SPI index and R/S analysis. The results showed that: 1) In past 54 years, the inter-annual variation of droughts showed by SPEI was the same as that showed by SPI before 2000, however, the trends showed by SPEI and SPI were opposite after 2000. The SPEI index showed that the spring and summer droughts gradually increased after 2000, while the SPI index indicated that the spring droughts were relieved after 2000. The temperature is the main reason for the differences between the two indices. 2) The trends of drought coverage area indicated by the two indices were consistent with the inter-annual variations of droughts that there was great difference before and after the mid 1990s. After the mid 1990s, the drought coverage area disclosed by SPEI was broader than that disclosed by SPI. 3) The trends of frequencies of spring and summer droughts indicated by SPEI and SPI were also opposite after 2000. The SPEI index discloses a high frequency period of droughts in 2000s, while the SPI index disclosed a low frequency period. However, both indices displayed that the high frequency area of spring droughts moved from west to east, and the high frequency area of summer droughts moved from northwest to southeast. 4) According to drought cycles and R/S analysis, spring drought will increase in the future 4-6 years and the high frequency area will be in the north; summer drought also will increase in the future 18-22 years and the high frequency area will be in the east and west. 5) The comparative analysis found that SPEI index is more suitable in this area.