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甘肃河东玉米种植区属于旱作雨养农业区,农作物生长主要依靠自然降水来维持,春夏干旱是影响该区玉米生长发育的关键因素。利用河东地区13个气象站点1957—2012年气象资料,基于标准化降水蒸散指数从干旱趋势、周期、空间特征及其与环流因子关系方面探讨近56 a来河东玉米种植区春夏干旱演变特征。结果表明:近56 a河东玉米种植区春夏两季均呈干旱化趋势,并自20世纪90年代中期以后,干旱呈加重趋势。干旱变化共经历了3个气候阶段,20世纪80年代之前,春夏旱情较轻;80年代—90年代,夏旱较春旱严重;2000年以后,春旱较夏旱严重。干旱周期变化,春夏干旱周期分别为20 a和14 a,干旱周期性变化主要是受太阳黑子活动影响。春夏干旱发生频率在突变前后差异显著,低频区在突变后转为高频区,易旱区呈扩大状态。ENSO事件是影响该区春夏干旱发生的主要环流因子,尤其对夏旱影响最为显著。近20 a来ENSO事件增强是该区干旱事件不断加重的原因,ENSO暖事件爆发时,该区春夏趋于干旱,由湿向干转变;ENSO冷事件爆发,干旱则有所缓解,由干向湿转变。
The planting area of corn in Hedong, Gansu Province is a rainfed agricultural area, and the crop growth mainly depends on the natural precipitation. The spring and summer drought is the key factor affecting the corn growth and development in this area. Based on the meteorological data of 13 meteorological stations in Hedong area from 1957 to 2012, the evolution characteristics of spring and summer droughts in the Hedong maize planting area in the recent 56 years were studied based on the trend, period and spatial characteristics of drought and its relationship with circulation factors. The results showed that in the recent 56 years, the Hedong corn planting area showed aridity in spring and summer, and the drought tended to increase after the mid-1990s. The drought experienced a total of three climatic stages. Before the 1980s, the drought was light in spring and summer. In the 1980s and 1990s, the summer drought was more severe than that in spring. After 2000, the spring drought was more severe than the summer drought. Drought period changes, spring and summer drought periods were 20 a and 14 a, cyclical changes in drought are mainly affected by sunspots activities. The frequency of drought in spring and summer was significantly different before and after the mutation. The low frequency region was changed to high frequency region after mutation, and the drought-prone region was in an enlarged state. The ENSO event is the main circulation factor affecting the spring and summer drought in this area, especially the summer drought. During the past 20 years, the increase of ENSO events is the reason of the increasing drought event in this area. During the ENSO warm event, the spring and summer of this area tended to be dry and changed from wet to dry. The ENSO cold event broke out and the drought eased, Change to wet.