基于SPEI指数的新疆天山草地近55 a干旱特征

Drought Trend over the Grasslands in the Tianshan Mountains,Xinjiang in Recent 55 Years Based on SPEI

标准化降水蒸散指数(SPEI)通过标准化潜在蒸散与降水的差值,表征一个地区干湿状况偏离常年的程度,是分析干旱演变趋势的新的理想指标,目前已经广泛应用于干旱评估、水资源管理等领域。利用SPEI和1961—2015年新疆天山山区8个代表站点的月降水量及月平均气温资料,对天山山区55 a以来气温和降水的变化特征、不同时间尺度的干旱变化特征、草地生长季干旱特征及变化趋势进行了分析,结果表明:近55 a,天山山区气温呈现显著的上升趋势;降水量总体呈略微上升的趋势,但年际变化较大,变化趋势不显著;天山山区月、季、半年尺度以及年尺度的干旱事件分别为42个、25个、16个和7个;天山山区草地生长季发生轻度、中度和重度干旱的频率分别为37. 5%、7. 1%和1. 8%;近55 a,天山山区草地生长季降水量有所增加,但由于气温升高带来的蒸散作用加强,气候仍呈变干的趋势。近55 a来,天山山区草地生长季气候存在变干的倾向,且年际间的干旱程度变化剧烈,对草地的年际间生长状况差异存在较大的影响。

Calculated by standardizing the difference between potential evapotranspiration and precipitation,the standardized precipitation evapotranspiration index(SPEI)shows the drought degree deviation from normal conditions.As an ideal indicator for analyzing the drought evolution trend,SPEI is widely used in drought assessment,water resources management and other fields.The characteristics of the temperature,precipitation,temporal distribution and variation of the temperature,precipitation,slight,moderate and severe drought frequencies and their trends in growing season of grasslands were analyzed using the SPEI method based on the monthly mean air temperature and monthly precipitation at 8 meteorological stations over the Tianshan Mountains in Xinjiang during the period from1961 to 2015.Results showed that the annual temperature in the study area was in a significant increase trend in recent 55 years.The precipitation was generally in a slight increase trend with a larger inter-annual variability,but the change trend was not significant.The numbers of drought events at monthly,seasonal,semi-annual and annual scales in the Tianshan Mountains were 42,25,16 and 7 respectively.The frequencies of slight,moderate and severe drought in growing season of grasslands were 37.5%,7.1%and 1.8%respectively.In recent 55 years,the climate over the grasslands in the Tianshan Mountains in growing season of grasslands became dry,and the annual degree of drought changed dramatically,which affected significantly the growth of the grasslands.