中文摘要：

通过对1644-1949 年间陕北地区自然灾害史料的收集整理与分析,研究了该区域旱灾的等级、发生频率、分布特征、致灾原因等.经统计,该区共发生旱灾131 次,发生频率为2.34 a/ 次.旱灾阶段性明显：1644-1743年间以轻度旱灾为主,灾害频率较低;1744-1823 年间中度旱灾增加,轻度中度旱灾交替发生,旱灾频次提高;1824-1949 年间,灾害频次大幅增加,大旱灾和特大旱灾频繁发生,灾情持续时间延长,呈现频次逐渐增加、等级逐渐升高的趋势.从发生季节看,夏季是旱灾发生的主要季节,次为春季和秋季.从地域分布上看,旱灾的发生频率呈现出由北向南逐渐降低的特征.该区旱灾的发生与气候波动有直接关系,降水量减少是诱发该区大旱灾和特大旱灾的主要原因,而降水分配不均则是轻度和中度旱灾的主要原因,过度的农业开发则加剧了旱灾的危害程度.

英文摘要：

Based on historical documents and data of drought in Northern Shaanxi from 1644 to 1949, the paper studied the regional drought grade, the frequency, distribution characteristics, reason and so on. The results indicate that there is 131 times drought and once every 2.34 a occurred in Northern Shaanxi. The drought has distinct stages:1644-1735, there is low and middle drought disasters in the area and disaster situation is also small;1736-1820, the middle drought disasters is increasing, but disaster frequency decreases and the interval increases;1821-1949, big and large drought disasters occurred frequently and extended duration. Summer is the main season of drought, the second is the spring and autumn. From the geographical distribution, there is higher frequency in northern region a-bout drought occurrence than southern. The frequency of drought closely related with climate fluctuation, it is the main reason of major and serious drought, the reduced rainfall, the precipitation distribution are the main reasons for mild and moderate drought, and excessive agricultural development exacerbated the degree of harm of drought.