中文摘要：

利用1980—2014年黄土高原52个气象台站观测的降水资料,计算得到了标准化降水指数（SPI）,进而比较了黄土高原不同地区近35年春季干旱的时空变化特征。研究发现：春季SPI与春季降水的时间变化较为一致,二者都能反映出1995年,2000年和2001年的三次较严重的春旱,且二者在1980—2014年间均呈线性减少的趋势。同时,黄土高原春季降水与春季SPI的空间分布却存在一定差别,这主要是因为春季降水的概率密度分布特征在不同站点存在差异。黄土高原北部,一次春季降水量少的发生概率较大,而在高原南部,较大降水概率则对应较多的降水量值。所以,对于黄土高原整体而言,当各区域春季降水偏少,且降水量值相等时,高原南部的春旱更严重;但当各地区春季降水异常量相等时,则在高原北部春旱等级较高。因此,未来黄土高原的春旱不仅受降水量控制,还与春季降水概率密度的分布特征关系密切。

英文摘要：

Based on the observed precipitation with 52 meteorological stations from 1980 to 2014,the standardized precipitation index（ SPI） within the Loess Plateau was calculated. Then the SPI was used to compare the temporal and spatial variation of the spring drought in different regions of the Loess Plateau in recent 35 years.The results showed that the temporal variation of SPI and precipitation in spring were similar. Both of them captured three severe drought events happened in 1995,2000 and 2001; And their linear trends for 1980—2014 were negative. However,the spatial patterns of spring precipitation and spring SPI were different due to the difference of the probability density distribution about spring precipitation with different stations. The probability of light precipitation is higher in the northern than in southern Loess Plateau,and the heavy rainfall is more likely to happen in the southern region. For the whole Loess Plateau,if the spring precipitation is short but equal for everywhere in Loess Plateau,then the southern region might meet a severe drought measured by SPI. If the precipitation anomaly is negative and equal for everywhere,then the drought is more severe in the northern region. Therefore,the level of spring drought in the Loess Plateau are not only controlled by the amount of spring precipitation,but also determined by the probability density distribution of precipitation for different regions.