Spatial and temporal variations of drought in Henan province over a 53-year period based on standardized precipitation evapotranspiration index

Abstract

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 recorded in Anyang, and the minimum occurred in Zhumadian, at 22.18% and 16.60%, respectively. The factors with the greatest influence on drought occurrence are increasing temperatures, the Eurasian atmospheric circulation patterns, and the El Ni?o effect.