黔东南夏季旱涝指数及干旱气候特征分析

Summer Drought/Flood Index and Climatic Features in Southeastern Guizhou Province

用当前降水和蒸发因子以及前期降水因子定义了黔东南夏季旱涝指数，用此指数计算了黔东南1971～2000年的夏旱指数，同时对各年的夏季旱涝进行了定级，检验证明，此指标对黔东南夏季旱涝等级的划分比日常业务中使用的降水百分率对黔东南夏季旱涝的等级划分更符合实际情况。讨论了黔东南夏季干旱的时空变化特征，得出结论：①夏季干旱主要出现在7～8月，6月干旱较轻，7月重早出现的概率最大，8月次之；②20世纪70年代干旱主要出现在7月，80年代整个夏季均少雨干旱，以中等以上干旱为主，90年代降水较多，没有重旱出现；③黔东南州的夏季干旱，东南部出现的概率最大，西北部最小；但7月干F旱多出现在东北部地区，8月的干旱西北部和东南部多于西南部和东北部。

The summer drought/flood index in Qiandongnan is defined by means of the precipitation and evaporation data as well as the prophase precipitation, and the indexes from 1971 to 2000 are calculated and graded for each year. It is found that the index is more applicable in practice. An analysis is made of the temporal and spatial distribution of summer droughts in Qiandongnan. Results show that ① Severe droughts occurred mostly in July and August, least in June. ② Droughts occurred mainly in July in the 1970s, in whole summer in the 1980s mainly with medium intensity, and rarely in the 1990s without severe droughts. ③ Summer droughts occurred most frequently in the southeast of Qiandongnan, and the least in the northwest part; but droughts occurred more frequently in the northeast part in July, and in the southeast and northwest parts in August.