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通过对历史文献资料的收集、整理统计和分析,对1368-1949年西海固地区干旱灾害的等级序列、时间序列变化、平均发生时间间隔和干旱变化趋势拟合进行了研究。结果表明:1368-1949年西海固共发生干旱灾害132次,平均每4.41年发生一次;其中以1800-1849年和1900-1949年这两个50年段的干旱灾害最为频繁。1368-1949年西海固干旱灾害以中度旱灾和轻旱涝灾为主,发生频次分别为58次、52次,占干旱灾害发生年总数的43.94%、39.39%。大面积的干旱灾害(三、四级)平均每26.5年出现一次,占干旱灾害发生总年数的16.67%。受季节性气候影响,西海固干旱灾害呈现出明显的季节性差异。夏季是干旱灾害最为频繁,春、秋两季次之,冬季最少。伏旱造成的危害相对比较严重。1368-1949年西海固干旱灾害发生频次的距平百分比曲线呈明显的波浪线型增长;以1700年为界,西海固干旱灾害频次呈明显的增加趋势,后期250年的干旱灾害发生频率是前期330年的2.62倍。西海固干旱灾害频发主要是由气候的异常波动、降水的年际、年内分布不均以及特殊的地理位置这些自然因素造成的;人类对自然环境的不合理改造和不科学的利用方式也加剧了干旱灾害的发生及成灾程度。
Through the collection, sorting and analysis of historical documents, the paper studied the rank order, time series change, average occurrence interval and trend of drought in Xihaigu area from 1368 to 1949. The results showed that a total of 132 drought disasters occurred in Xijiangu during 1368-1949, with an average of 4.19 years. Among these 50 years, the disasters were most frequent in 1800-1849 and 1900-1949. In the period of 1368-1949, the dry and drought disaster in the West China Sea was moderately dry and lightly droughted, with 58 and 52 times respectively, accounting for 43.94% and 39.39% of the total number of the year in which the drought disaster occurred. Large-scale drought disasters (Grade III and IV) occur once every 26.5 years, accounting for 16.67% of the total number of drought disasters. Affected by the seasonal climate, the seasonal drought in the West China Sea showed obvious seasonal differences. Summer is the most frequent drought disaster, followed by spring and autumn, the least in winter. The damage caused by the drought is relatively serious. From 1368 to 1949, the average percentage of anomalies of the occurrence of the solid and dry spell in the West China Sea showed an obvious wave linear growth. From 1700 to the present, the frequency of the solid and dry spells in the West China Sea increased markedly. The frequency of the drought disaster in the later 250 years was the earlier period 330 times the 2.62 times. The frequent occurrence of drought and drought in the Western China Sea is mainly caused by the natural factors of anomalous fluctuations in climate, annual precipitation, uneven distribution during the year and special geographical locations. The human unreasonable transformation of the natural environment and unscientific utilization methods also intensify The occurrence of drought disaster and degree of disaster.