利用陕西黄土高原地区68个气象站降水资料,选择标准化降水指数（SPI）为干旱指标,分析了该地区最近40年（1971—2010年）的月、季、年干旱特征,在此基础上利用经验正交函数(EOF)分解方法进行了干旱分区,并分析了全年及各季节干旱站次比和干旱强度的年际变化。结果表明:EOF分解第1、2、3特征向量分别反映了陕西黄土高原地区干旱的一致变化、南-北反向分布和中部-南北反向分布的不同特点;年度干旱站次比和干旱强度有明显的阶段性分布特点,在年代之间有重-轻-重-轻的变化趋势。2001年以来,年度和夏、秋、冬季干旱强度都有不同程度降低,春季干旱有增强趋势。陕北和关中地区的春季、夏季干旱变化趋势相反,秋季、冬季干旱变化趋势一致。地区平均每年出现干旱月3.8个,几乎每年都有干旱月出现,最多的一年可出现6—9个干旱月。

According to the precipitation data from 68 meteorological stations in the Loess Plateau Area of Shaanxi, the drought characteristics during 1971-2010 of the studied area was analyzed at scale of month, season and year based on the standardized precipitation index(SPI), and its spatial pattern was analyzed using the EOF method, and the inter-annual and inter-decadal change of the percentage of drought stations and drought strength were also analyzed at scale of month, season and year. The results showed that the first, second, third feature vector reflected different drought characteristics in the Loess Plateau Area of Shaanxi, and the first feature vector indicated consistency of drought characteristics in different sub-areas, the second feature vector indicated north-south opposite pattern of drought characteristics, the third feature vector indicated opposite pattern of drought characteristics between middle sub-area and northern and southern sub-area. The percentage of drought stations and drought strength showed obviously changing trends of heavy drought-light drought-heavy drought-light drought during 1971-2010 in the Loess Plateau Area of Shaanxi. Since 2001, the drought strength reduced by different rates in summer, autumn, winter, but the drought strength increased in spring. The drought strength in spring and summer showed opposite trend between the north Shaanxi and middle Shaanxi, and drought strength in autumn and winter showed consistent trend between the sub-areas. There were 3.8 dry months per year on average in the Loess Plateau Area of Shaanxi, and there was one dry month at least every year, and there was 6-9 dry months at most.