明代固原地区干旱灾害研究

通过对明代固原地区历史资料的搜集、整理、分析,对其干旱灾害等级化及成因等问题进行了研究。结果表明,固原地区自1368年到1644年间的277 a中,共发生干旱灾害118次,平均每2.35 a发生1次;其中轻度旱灾20次,占旱灾总数的16.9%;中度旱灾38次,占旱灾总数的32.3%;大旱灾42次,占旱灾总数的35.6%;特大旱灾18次,占旱灾总数的15.2%。该地区旱灾可分为4个阶段:第1阶段的1368-1424年和第3阶段的1505-1604年是旱灾的低发期;第2阶段的1425-1504年和第4阶段的1605-1644年是旱灾的高发期。该地区旱灾的季节性特征是单季旱占55.9%,其中夏旱所占比重最高,春旱、秋旱次之,冬旱较为稀少;季节性连旱占44.1%,其中春夏连旱和春夏秋3季连旱分别高达17.8%、15.3%。该地区明代处于气候的干冷期,年降水量减少是发生旱灾的主要原因。固原地区具有指示该时代气候变化特征的5次干旱气候事件,分别是明代的1437-1442年、1481-1490年、1608-1617年、1627-1634年、1637-1641年。

Drought Disasters in the Guyuan Region of Ningxia Province in Ming Dynasty

Based on statistics of the drought events recorded in historical documents,the temporal distribution,degree and causes of drought disasters in Guyuan region of Ningxia Province in the Ming Dynasty(1368-1644) were analyzed in this paper.Results showed that 118 drought disasters,or once every 2.35 years,occurred in Guyuan in the Ming Dynasty.In this region,the slight drought accounted for 16.9% of the total droughts,the moderate drought accounted for 32.3%,the severe drought accounted for 35.6%,and the very severe drought accounted for 15.2%.Occurrence of drought disasters in Guyuan in the Ming Dynasty can be divided into four main periods: the first phase of 1368-1424 and the third phase of 1505-1604,when the frequencies of drought disaster were relatively low;the second phase of 1425-1504 and the forth phase of 1605-1644,when the frequencies of drought disaster were relatively high.The drought disasters had obvious seasonal difference and the single-season drought frequency was 55.9%.Drought disasters occurred in summer was the most,that in spring and autumn second,and that in winter the least.The continuously seasonal drought frequency was 44.1%,of which the spring-summer continuous drought disasters were up to 17.8%,and the spring-summer-autumn continuous drought disasters were up to 15.3%.Climate was much drier and colder in the Ming Dynasty in this region,and annual precipitation reduction was the main reason for the drought.We determined 5 draught events in Guyuan region in the Ming Dynasty,which indicated the five periods of climate changes in Guyuan region in 1437-1442,1481-1490,1608-1617,1627-1634,and 1637-1641.