近500年陕西旱涝序列重建与趋势分析

本研究旨在运用历史文献资料和降水资料恢复重建陕西省各气象站1470—2008年旱涝等级,分析其变化的基本特征及其演变趋势,为将来的旱涝预测提供依据。选取榆林、延安、西安、汉中、安康5个有代表性的站点,分析这5个站1470—2008年长达539年的旱涝等级序列发现:榆林和延安有由旱向正常发展的趋势;宝鸡和西安旱涝交替阶段性变化显著,存在偏旱向偏涝转变的趋势;而陕南的汉中和安康539年来主要以偏涝为主。17世纪40年代前后陕北、关中和陕南先后出现了旱涝突变点,其中,陕北1640年前后有由偏旱转为正常的突变;1643年前后宝鸡和西安发生偏旱转为偏涝的突变;而汉中和安康在1648年前后发生了正常向偏涝的突变。对陕西5个站点539年的旱涝级别的时间序列进行EOF分解,前三模态方差贡献达91%,反映了陕西全省旱涝时空分布的主要特征;第一模态方差贡献为60.3%,这539年陕西全省旱涝一致型占主导地位;第二模态方差贡献为19.8%,即南北旱涝相反型;第三模态方差贡献较小,为10.9%。

The reconstruction and trend study of Shaanxi province's drought and floods grade in recent 500 years

This article rebuilds the drought and floods grade of Shaanxi province''s stations from 1470 to 2008, by using the historical documents and precipitation data. It analysis the basic features and evolution trend, and provides basis for forecast of drought and floods. There are five typical stations picked up that are Yulin, Yan''an,Xi''an, Hanzhong, Ankang. By analyzing 539 years drought and floods grade of five stations from 1470 to 2008, Yulin and Yan''an have the trend which is from drought to normal. Baoji and Xi''an has significant alternating of droughts and floods and the trend which is from drought to floods. The trend of Hanzhong and Ankang is mainly floods. The change points of drought and floods came out in southern, northern Shaanxi and Guanzhong in about 1640s. The change of southern Shaanxi is from drought to normal in about 1640. The change of Baoji and Xi''an is from drought to floods in about 1648. The change of Hanzhong and Ankang is from normal to floods. The time sequences of 539 years'' drought and flood in 5 Shaanxi stations are decomposed by EOX. The first three EOF modes make a contribution accounting for 91% of the total variance. The first EOF makes a contribution accounting for 60.3%. The concordant form takes the leading position of all these years. The second EOF contributes 19.8%, it is the opposite type of drought and flood between south and north. The third EOF contributes 10.9%.