基于SPEI的陕北黄土丘陵区干旱特征及影响因素分析

为探讨陕北黄土丘陵区干旱特征及其影响因素,借助绥德2000-2014年逐日的气象数据,基于Hargreaves、Thornthwaite和Penman-Monteith蒸散模型及同一套降水资料计算,获得不同时间尺度(月、半年和年)3种标准化降水蒸散指数(SPEI),对比分析上述3种SPEI的差异并选取适宜于陕北黄土丘陵区的SPEI,而后采用SPEI分析干旱特征,并利用通径法分析气象因子对SPEI敏感性。结果表明:1)基于Penman-Monteith蒸散模型的SPEI(SPEI-PM)能够准确反映陕北黄土丘陵区干旱事件,与SPEI-PM相比,基于Hargreaves和Thornthwaite的SPEI值偏低,计算误差为0.26～0.38;2)干旱变化呈现减弱趋势,短时间尺度上(1和6个月)SPEI-PM值变化频繁,长时间尺度上(12、18和24个月)SPEI-PM值变化幅度小且变化周期长;3)在月、半年和年尺度上对SPEI-PM影响程度最大的气象因素分别为气温和相对湿度。

SPEI Based Drought Characters and Factors in Loess Hilly Regions of Northern Shaanxi

In order to explore the drought characteristics and influencing factors in loess hilly region of Northern Shaanxi Province,three types of standardized precipitation evapotranspiration index (SPEI-HG,SPEI-TW,SPEI-PM) in different time scales (month,half year and year) were calculated using precipitation and three sets of potential evapotranspiration (ET) data based on daily climatic data collected from meteorological station of Suide in Shaanxi during 2000 to 2014.The ET was calculated by Hargreaves,Thornthwaite and Penman-Monteith formulae,respectively.Differences between the three types of SPEI were compared and an appropriate SPEI was selected.The drought characteristics were analyzed by the selected SPEI,and the sensitivity of meteorological factors to the selected SPEI was analyzed by path analysis.The results showed that 1) SPEI-PM could accurately describe drought events in loess hilly region of Northern Shaanxi Province.Compared with SPEI-PM,the SPEI-HG and SPEI-TW underestimate drought and the mean absolute errors were 0.26~0.38.2) Drought change showed a decreasing trend,SPEI-PM fluctuation was frequent in short time scale,and stable in long time scale.3) Meteorological factors that mainly affected SPEI-PM on the scale of monthly,half-year and year were the temperature,temperature and relative humidity,respectively.