Reconstruction of Series in Later or Earlier Starting Date of Rainy Season in Yunnan Province and Evolvement of Summer Monsoon in Qing Period

Based on year by year examination and correction of files-dominated historical documents and verification of various kinds of data,the later or earlier rainy seasons in Yunnan from 1711 to 1911 has been reconstructed.The analysis indicates that there are obvious interannual and interdecadal fluctuations in the starting date of rainy seasons in Yunnan,as well as long-term fluctuations exceeding the interdecadal scale.It comes earlier from the beginning of the 18th century,later in the 19th century and earlier again in the 20th century.This reflects to a certain degree the gradual change of the summer monsoon in Yunnan.There exist obvious quasi-3 years and 11.3 years cycles for starting date of raining seasons in Yunnan,the quasi-3 years might be related to the El Nino's quasi-3 years cycle while the 11.3 years being visiblely related to the 11 years cycle of solar activity.Meanwhile,the dissertation finds that the El Nino plays a very important role in the starting date of rainy seasons in Yunnan.The starting date of rainy seasons in Yunnan often comes later or normally in the year of El Nino.However,in the period when such influence weakens obviously,this means that ENSO may exert certain impact on Asian summer monsoon.