基于传统干湿指数的省域长历时气象干旱变化特征及其对旱作粮食单产的影响

干旱是陕西省主要的气象灾害之一,干旱频发对农业生产、社会经济发展和生态环境等诸多方面均造成了严重影响。通过选取陕西省22个气象站点1960-2017年逐日地面气象数据,基于传统的潜在蒸散与降水量之比构成的干湿指数,由FAO56-PM潜在蒸散量对干旱指标进行重新界定,从长时序上分析了陕西省气象干旱的时空变化特征。结果表明:(1)由FAO56-PM公式重新界定的湿润、半湿润、半干旱、干旱、干燥气候分区界限值分别为0.58,1.17,1.77,2.36,4.74,全省大多数地区年干燥度呈增加趋势,主要集中在陕北南部与关中地区;(2)全省各站点多年平均年干燥度整体呈由北向南逐渐减小分布,干湿气候界线年代际波动较明显;(3)全省多年干旱发生频率整体呈增加趋势,分布情况为从陕北向关中先逐渐减小后又略微增大,再从关中向陕南又逐渐减小。春、秋、冬季干旱频率都为增加趋势,夏季为减少趋势;(4)省内北部干旱程度大于南部,不旱年数从陕南向陕北依次减少,微旱多发于陕南地区,中旱为关中地区,大旱为陕北地区,微旱和中旱多发于夏季,大旱主要发生于冬季与春季;(5)以旱作为主的陕北地区干燥度与降水量对单位面积粮食产量的影响较为显著。

Spatiotemporal Variation of Long-term Meteorological Drought and Its Impacts on Grain Yield in Shaanxi Province Based on the Traditional Arid-Wet Index

Drought is one of the major meteorological disasters in the Shaanxi Province. Frequent drought has a serious impact on agricultural production, social and economic development, ecological environment and other aspects. Based on the daily meteorological data of 22 selected weather stations in the Shaanxi Province during 1960-2017, using the traditional aridity index as the meteorological drought index, we redefined the aridity threshold via potential evapotranspiration(ET0) calculated by the FAO56-Penman-Monteith equation, and analyzed the spatiotemporal variation of long-term meteorological drought in Shaanxi Province. The results are as follows. First, the climate boundaries between the humid, semi-humid, semi-arid, arid and dry, redefined by the FAO56-PM equation, were 0.58, 1.17, 1.77, 2.36 and 4.74, respectively. The variation of annual aridity index of most stations showed the increasing trend, especially in the northern Shaanxi and Guanzhong areas. Second, the average annual aridity index of all stations in the province decreased gradually from north to south, and the inter-decadal variation of the arid-wet climate boundary was obvious. Third, the occurrence frequency of drought showed the increasing trend in the whole province. Spatially, it gradually decreased then slightly increased from Shaanbei area to Guanzhong area, and then gradually decreased from Guanzhong area to Shaannan area. Seasonally, the occurrence frequency of drought increased in spring, autumn and winter, but decreased in summer. Fourth, the degree of drought in the northern area of the province was greater than that in the southern area of the province;however, the number of non-drought years decreased successively from Shaannan area to Shaanbei area. The mild drought and moderate drought mainly occurred in the southern area of the province in summer, while the severe drought occurred in the northern area of the province in winter and spring. Fifth, the influence of aridity and precipitation on grain yield in Shaanbei area was significant.