中文摘要：

干旱在中国发生较为频繁,对农作物的影响较大。基于1961-2013年实测气象资料,利用标准化降水蒸散指数（SPEI）定量分析了河南省不同时间尺度干旱发生频率和发生强度,揭示了该地区干旱发生的时空演变特征及干旱发生的原因。结果表明：SPEI值能较好地反映河南省干旱的变化特征;随着时间尺度的减小,SPEI值波动幅度增加,干旱发生频率增加。近53年河南省干旱发生频率总体呈上升趋势,且各地区之间分布不均匀。周口地区发生频率最高,达35%以上;豫中和豫西地区最低,为26%左右。四季中以春、夏两季干旱发生最为严重,其次为秋季,冬季最弱。在年际变化方面,1966-1968年、1998-2000年和2011-2013年发生了大范围的持续干旱。干旱发生强度呈现豫北和豫西偏东地区高,豫东和豫南北部地区低特点;干旱发生强度最强的地区为安阳,为22.18%,最弱的地区为驻马店,为16.60%。

英文摘要：

Drought, one of the most complex natural hazards, affects agriculture, water resources, natural ecosystems, and society. The negative societal consequences of drought include severe economic losses, famine, epidemics, and land degradation. However, there are few studies on the complexity of drought characteristics, both at multiple time scales and with variations in evapotranspiration. In this study, drought occurrences were quantified using a new drought index, the standardized precipitation evapotranspiration index（SPEI）, based on observed meteorological data of monthly mean temperature and precipitation from 1961 to2013 in Henan province, central China. This can help decision- makers improve their level of preparedness and adopt appropriate policies for agricultural management. Based on the SPEI values of each weather station in the study, the frequency and severity of meteorological droughts were computed, and the monthly, seasonal, and annual drought frequency and intensity over a 53- year period were analyzed. The spatial and temporal evolution, intensity,and the primary causes of drought occurrence in Henan were revealed. The results showed that the SPEI values effectively reflected the spatial and temporal pattern of drought occurrence. As the time scale decreased, the amplitude of the SPEI increased and droughts became more frequent. Since 1961, drought has occurred at the annual, seasonal, and monthly scales, and the occurrence of drought has increased. However, regional distribution has been uneven. The highest drought frequency, 35%, was observed in the Zhoukou region, while the lowest value,26%, was measured in the central and western parts of Henan. The most severe seasonal droughts occurred in the spring and summer months, followed by autumn. Annually, wideranging droughts occurred in 1966- 1968, 1998- 2000, and 2011- 2013. The drought intensity distribution showed higher values in northern and western Henan, and lower values in its east and south. The maximum drought intensity value was record