Studying the evolution of regional dry climate is the premise of drought resistance and disaster alleviation. To study the drought evolution trend during interannual change, seasonal variation and spatial diversity, 38 years’ meteorological data from 42 observation stations in the rain-fed farming area of the Loess Plateau was used by means of amended palmer drought index, wavelet analysis, and EOF (empirical orthogonal function decomposition). The results showed that drought intensified during interannual change and seasonal variation which was significant after 2003. The frequency of drought period was diminished with interannual change and seasonal variation. During the four seasons, the highest effect on annual drought was found in spring which followed by summer and autumn. On the whole, the Loess Plateau tended to get increasingly drier, but there was intensity and phase differences between north and south, east and west, and the central plateau and the surrounding area. In the area north of Hengshan and Jiaxian counties, drought was alleviating and showed normal change, while in the south region drought tended to intensified, particularly in Suide and Wubu counties. This study has certain theoretical significance and practical values for guiding the cropping system of drought resistance and disaster alleviation on the Loess Plateau.%研究区域气候干旱的变化规律,是制订农业抗旱减灾的前提.利用陕西黄土高原旱作农区42个站点38年的气象观测资料及修正的palmer干旱指数、小波分析和EOF(经验正交分解函数)等分析方法,研究陕西黄土高原旱作农区年际、季节及空间上干旱变化趋势.结果表明:干旱在年际与季节性变化的趋势,都趋于干旱化变化,在2003年后具有明显干旱化的特征;年代和季节都具有干旱化周期性频率逐年交小的趋势;在四个季节中,春季干旱变化对全年的贡献最高,其次是夏季、秋季.在空间上,陕西黄土高原基本趋向干旱化方向,但强度、位相等存在南北、东西差异,高原中部和四周之间的差异.横山-佳县以北地区呈正态变化,干旱趋于缓和,南部地区干旱趋干加剧,尤其绥德、吴堡一带.本研究结论对指导陕西黄土高原早作农区抗旱减灾型农作制具有重要的指导意义和实践价值.
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