兰州地区近540年旱涝灾害研究

Study on drought-flood disasters in Lanzhou area for recent 540 years

采用1470～2000年旱涝史料,选取兰州、榆中和永登气象资料,将旱涝等级资料延续到2009年建立兰州地区近540年旱涝等级序列,对旱涝灾害发生的规律性、周期性、阶段性和形成原因进行了分析。结果表明:近540年兰州地区共发生旱灾145次,涝灾90次;根据旱涝灾害发生频次可将近540年划分为前期和后期,前期是旱涝灾害低频期,后期是高频期;近540年兰州地区旱涝趋势以旱和偏旱为主,且出现三个以旱为主的上升阶段和四个以涝为主的下降阶段阶段性特点,旱涝存在3～4a周期、25～26a周期和81～82a周期,其中81～82a周期对应太阳活动的80～120a周期;文中初步将公元1581～1588年、公元1634～1641年和公元1926～1930年发生的旱灾确定为干旱气候事件。

YIistorical data of droughts and floods from A. D. 1470 to 2000, meteorological data of Lanzhou, Yuzhong and Yongdeng were collected to establish drought - flood hierarchical sequence in past 540 years in Lanzhou area. Regularitty, periodicity, stage and cause of drought - flood disasters were analyzed. The results showed that in past 540 years, 145 times of drought disaster hanpened and 90 times of flood disaster hanpened in Lanzhou area. Accroding to the frequency of drought - flood disasters, we divided the past 540 years into early and late periods. In early periods there was low frequency of drought -flood disaster, as to the late periods, there was the high frequency of drought - flood disaster. There were three rising phases mainly by drought and four downward phase mainly by flood. Drought -flood had 3 -4a, 25 - 26a and 81 - 82a cycles, the 81 -82a cycle corresponded to 80 - 120a cycle of the solar activity. The preliminary view was that three drought climate events happened in Lanzhou area in past 540 years, during A.D. 1581 - 1588, A. D. 1634 ~ 1641 and A. D. 1926 ~ 1930.