Abstract:

A modified drought index is defined as K based on the ratio of precipitation and evaporation，and the temporal and spatial distribution of drought disaster in Yueqing of Zhejiang Province was analyzed by using K index ten days by ten days．At the same time，comparison was made between K index and precipitation anomalies and results show that evaluation of the drought disaster by means of K index was more objective，and was basically identical with historical records of drought in Yueqing，but the degree of drought disaster evaluated by precipitation anomaly was partial light and would miss some of the severe drought events．The degree of drought disaster has relation with the temporal distribution of precipitation in the coastland．During a certain period ( 50 to 90 days) and under the same precipitation，it is not good for termination of drought event that the rainfall time is too centralized or too scattered．The analysis and calculation of ten days’drought index K can objectively reflect the temporal distribution of precipitation，soil moisture and drought situation

Key words: drought disaster, drought index, temporal and spatial distribution

摘要：

以降水量和蒸发量的比值定义干旱指数K，采用逐旬K 指数对浙江省乐清市干旱灾害的时空分布特征进行分析; 同时通过K 指数和降水量距平R 指标对乐清干旱灾害评估的对比分析得出结论。采用逐旬K 指数作为干旱指标计算干旱天数，再由干旱天数确定干旱灾害等级的评估方法较为客观，和历史记载的干旱灾情基本一致; 而采用时段降水量R 指标对干旱灾害程度评估偏轻，有可能漏掉中旱或大旱。在沿海多降水地区，干旱灾害的程度和降水量的时间分布有关，在某一时段( 50 ～90 d) 内，同样的降水量情况下，降水量短时间过于集中或随时间分布过于分散，都不利于该时段旱情的解除; 通过逐旬K 指数分析计算可较客观地反映降水量的时间分布及土壤水分和旱情的关系，使得干旱灾害评估较为接近实际。

关键词: 干旱灾害, 干旱指数, 干旱时空分布