Abstract
The quantitative reconstruction of the length of the rainy season and precipitation on the Tibetan Plateau(TP)is crucial for revealing the spatiotemporal evolution of the Westerlies and Asian summer monsoon,as well as its ecological and environmental effects.Accurately determining the start and end times of the rainy season on the Plateau remains challenging.This study determined the start and end times of the rainy season in different locations on the Plateau by identifying precipitation inflection points.We calculated the duration and precipitation amount of the rainy season and established a transfer function between the modem pollen assemblages and them.Then,we reconstructed the rainy season variations in Kusai Lake(northern TP)and Jiang Co(central TP)during the past two millennia.The results showed that,the rainy season precipitation in Kusai Lake recorded five periods of high precipitation:AD 580-680,1000-1100,1200-1450,1550-1780,and 1920-present,cor-responding to the stages with long rainy season.The rainy season precipitation sequence in Jiang Co recorded four periods of high precipitation:AD 80-500,800-950,1250-1450,and 1780-present,which is consistent with the long rainy season before AD 1000 but unclear afterward.Spatially,rainy season precipitation on the Plateau exhibited four patterns:"wet in both north and south"may be related to abnormally strong summer monsoons;"dry in both north and south"likely associated with weak Westerly wind and weak summer monsoon;"wet in the south and dry in the north"linked to strong summer monsoon and weak Westerly wind;and"dry in the south and wet in the north"connected to weak summer monsoon and strong Westerly wind.This study revealed the spatiotemporal evolution pattern of the rainy season onset and end,duration,and precipitation amount on the Plateau over the past two millennia.It provides natural background support for further understanding the coupling between Westerly wind and Asian summer monsoon.
基金项目
国家自然科学基金(41830322)
国家自然科学基金(42202217 & T2192954)
中国科学院战略规划重点项目(XDA2007010103)
中国博士后科学基金(2021M703195)