Change of Drought at Multiple Temporal Scales Based on SPI/SPEI in Northeast China
In this paper,the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI) were used to analyze the drought variation at multiple temporal scales and the difference between SPI and SPEI performance in northeast China (Heilongjiang,Jilin and Liaoning provinces),the two indexes were calculated using the daily ground observation data including the average air temperature,precipitation,sunshine duration,average relative humidity,average wind speed and average vapor pressure at 90 meteorological stations during the period of 1960-2014.The results are as follows:① The study area was divided into 5 subareas according to REOF method based on annual precipitation,there was no significant trend of annual precipitation in all the subareas,but the annual evapotranspiration was significantly in a decrease tend in subarea Ⅰ,subarea Ⅱ,subarea Ⅳ and an increase trend in subarea Ⅴ;② SPI/SPEI values fluctuated frequently at a 1-month scale,and the persistent drought and wet durations formed with the increase of temporal scale,in which the drought duration was slightly longer than the wet duration.Generally,SPI and SPEI performed the similar results in evaluating drought at all the time scales,SPI fluctuated widely at shorter time scales,because it was easily affected by precipitation,whereas the drought degree of SPI was underestimated compared with that of SPEI at longer time scales.In 1982 and 1999 when severe drought occurred,the capability of indicating drought by SPI descended in some areas where precipitation was significantly decreased or in some months when the similar situation occurred;③ The occurrence frequencies of non-drought and extreme drought described by SPI were higher than that by SPEI in northeast China,but the situation was opposite in describing the moderate drought,severe drought and humidity;④ SPEI was more suitable than SPI in evaluating drought and flood in northeast China.
standardized precipitation indexstandardized precipitation evapotranspiration indexMulti-scaleDrought variationNortheast China