基于SPI/SPEI指数的汉江流域1961~2014年干旱变化特征分析

Characteristics of Drought Variations in Hanjiang Basin in 1961-2014 Based on SPI/SPEI

摘要: 本文采用汉江流域13个气象站1961~2014年逐日气象数据(降雨、温度、相对湿度、日照时数和风速)，利用标准化降水指数(SPI)和标准化降水蒸散指数(SPEI)两个干旱指标，分析了1961~2014年汉江流域的干旱变化特征。结果表明：(1) 近54年来，汉江流域年降水量呈不显著下降趋势，年参照蒸发量呈显著减少趋势(−7.7 mm/10 a)，SPI指数总体上呈不显著下降趋势，而SPEI指数呈不显著上升趋势；(2) 1个月尺度的SPI指数的正负波动范围较SPEI大，随着时间尺度延长，SPI/SPEI发生干旱的持续时间增长，旱涝变化趋于稳定；(3) 流域无旱的累积概率超过65%，随时间尺度延长无旱发生的概率逐渐降低；(4) 流域最干旱的年份为1966年，最干旱年东南地区的干旱等级整体上比西北地区高，最湿润年为1983年，SPI/SPEI由西北向东南均呈现先减小再增大的趋势；在描述各站点干旱等级时，最干旱年SPEI描述的流域干旱等级整体上高于SPI，最湿润年SPI和SPEI描述的旱涝等级基本一致。

Abstract: To analyze the characteristics of drought variations in Hanjiang Basin, the standardized precipitation index (SPI) and the standardized precipitation evapotranspiration index (SPEI) were calculated by using daily meteorological data (including precipitation, temperature, relative humidity, solar duration and wind speed) from 13 meteorological stations across Hanjiang Basin for 1961-2014. Results showed that: (1) in the past 54 years, the annual precipitation showed a non-significant downward trend, while the annual evapotranspiration presented a significant downward trend (−7.7 mm/10 a); the SPI index demonstrated a non-significant downward trend, and the SPEI index with a non-significant upward trend; (2) SPI values with 1-month scale had a larger fluctuation range than SPEI values, and the SPI/SPEI drought duration extended as the time scale prolong; (3) over 65% of the basin was drought-free in 1961-2014, and the drought-free cumulative probability decreased as time scale extended; (4) the driest year in Hanjiang Basin was 1966, with higher drought grade in southeast region than in northwest region overall, while the 1983 was the wettest year, with SPI/SPEI values decreased and then increased from northwest to southeast. When describing the drought grade at each station, drought grades based on SPEI were higher than SPI as a whole in the driest year, while drought grades based on SPI and SPEI were basically consistent in the wettest year in Hanjiang Basin.