延安地区明代干旱灾害与气候变化研究

通过对陕西省延安地区明代（公元1368—1644年）历史资料的搜集和整理,对该时期干旱灾害等级、时间变化及成因进行了分析。结果表明：在明代的277年中,延安地区共发生干旱灾害91次,平均每3年发生1次。轻度干旱灾害发生17次,中等干旱灾害发生30次,大干旱灾害发生29次,特大干旱灾害发生15次,分别占到干旱灾害总数的18.7%、32.9%、31.9%和16.5%。大干旱灾害与特大干旱灾害发生频次高是明代延安地区干旱灾害的突出特点,指示明代总体为干旱气候期。延安明代干旱灾害可分为4个阶段,第一阶段为公元1368—1420年,为干旱灾害少发期;第二阶段为公元1421—1520年,为干旱灾害多发期;第三阶段为公元1521—1617年,为干旱灾害少发期;第四阶段为公元1618—1644年,为干旱灾害多发期。各等级干旱灾害特别是大与特大干旱灾害显著增加,指示第二、四阶段气候显著变干,降雨量明显减少。延安地区明代出现了2个极端干旱气候亚阶段,分别在1480—1499年和1626—1641年之间,当时年均降水量比现今少200 mm左右。

Drought Disaster and Climatic Change During Ming Dynasty in Yan＇an Area

Based on a compilation of historical data of drought disasters in Yan＇an Area during Ming Dynasty（1368-1644）,the temporal change,level and reason of drought disasters were analyzed.The results showed that during 277 years of Ming Dynasty,the drought disasters happened 91 times in Yan＇an Area,with average once every 3 years.The drought disaster happened 17,30,29 and 15 times for mild,middle,great and serious levels,respectively.The high frequency of both great and serious drought disasters was the outstanding feature of the climate during Ming Dynasty in Yan＇an Area,and indicated the climate was arid as a whole.The distribution of drought disasters in Yan＇an Area during the Ming Dynasty could be divided into four stages： from 1368 to 1420 with low frequency of drought disasters（the first stage）;from 1421 to 1520 with high frequency of drought disasters（the second stage）;from 1521 to 1617 with low frequency of drought disasters（the third stage）;from 1618 to 1644 with high frequency of drought disasters（the forth stage）.The significant dynamics of frequency of drought disasters among the four stages indicated that the climate in the second and fourth stages were obviously drier with decreased precipitation.In the second and fourth stages,there were two sub-stages of extremely dry climate（1480-1499,1626-1641）,in which the precipitation was 200 mm less than that in nowadays.