清代黄河中游、沁河和永定河入汛时间与夏季风强度

利用清政府布设在黄河中游三门峡万锦滩、沁河下游木栾店以及永定河下游石景山、卢沟桥的志桩水位记录,以首次涨水超过0.64m作为汛期建立的标志,在候尺度下恢复了其汛期建立时间距平序列。黄河中游、沁河下游和永定河下游序列分别开始于1766年、1736年和1761年。研究时段内,黄河中游和沁河下游平均在7月6~10日入汛、永定河则在7月16~20日。永定河相对较为稳定,显示出其上游雨季开始时间基本维持在7月初,而黄河中游和沁河却波动较大,早晚相差达3个月;黄河中游与沁河入汛距平波动的同相位现象在19世纪中期之后比较明显。1870~1900年代黄河中游、沁河和永定河入汛普遍延迟1个候左右,对应于黄土高原夏温偏低的时期;1820~1860年代黄河中游、沁河入汛偏早,则对应了黄土高原夏温偏高。

Onset of flood season in the middle reach of Yellow River,Qinhe River and Yongding River and summer monsoon strength in the Qing dynasty

The time series of flood season onset date anomalies are established on a pentad scale(or a 5-day scale) in the Qing dynasty.A water level rise of 0.64 m marks the beginning of a flood season.The historical water level records of the Qing Government are obtained for Wanjingtan near the Sanmenxia Gorge in the middle reach of the Yellow River,and Muluandian in the lower reach of Qinhe River,as well as Shijingshan and Lugouqiao Bridge in the lower reaches of Yongding River.The records start respectively in 1766,1736 and 1761 for the Yellow River,the Qinhe River and the Yongding River.During the study periods,the flood season usually started between July 6 and July 10 in the middle reach of the Yellow River and the lower reach of the Qinhe River;whereas in the Yongding River,the season normally started between July 16 and July 20.The starting date is found to be more stable in the Yongding River comparing to the other two rivers.This is due to the fact that the rainy season is very much regular in early July in the upstream region of the Yongding River.However,the rainy season showed a great deal of fluctuation for up to three months in the middle reach of the Yellow River and the lower reach Qinhe River.The synchronous phase fluctuation in flood season onset date anomalies was more significant in the middle reach of the Yellow River and the lower reach Qinhe River after the mid-19th century.The flood season was generally postponed by 5 days in all three rivers during the period 1870-1990,which corresponded well with relatively cool summer temperatures observed on the Loess Plateau.The opposite was true in the middle reach of the Yellow River and in the lower reach of Qinhe River,which also corresponded well with relatively high summer temperatures observed on the Plateau.