Characteristics Of The Tibetan Plateau Summer Monsoon And Its Trend In The Background Of Global Warming At 1.5?

This article is based on daily reanalysis data of NCEP/NCAR from 1961 to 2014 and CMIP5 mode data from 1961 to 2100.Calculate the Tibetan Plateau summer monsoon index and Tibetan Plateau heat source Q.Using the EEMD method to find out the characteristics of the Tibetan Plateau summer monsoon index and Tibetan Plateau heat source Q.Then discuss the correlation between the Tibetan Plateau summer monsoon index and Tibetan Plateau heat source Q.Finally,using the model data to estimate the changes of the Tibetan Plateau summer monsoon index.It is analyzed how warming affects the changes of the summer monsoon over the Tibetan Plateau.The following conclusions have been obtained:(1)The Tibetan plateau summer monsoon has structural characteristics of oscillation modes in different time scales over the past 54 years:the c1 component generally shows a quasi-period variation of 2 to 3 years;the c2 component shows a quasi-period of 10 years after the mid-1970s.The c3 component showed a 20-year quasi-period change before 1985,after which the amplitude and wavelength gradually decreased;the c4 component included a quasi-periodic change of up to 30 years,and the fluctuation range was relatively stable over the entire time span.The trend term r increases first and then decreases throughout the time scale,with the beginning of the 21st century as the demarcation point.When the plateau summer monsoon is abnormally strong(weak),the height field and the wind field in the plateau region all have obvious changes:the strong year plateau region is mainly controlled by positive height,and the low layer shows cyclonic upsurge;On the contrary,in the weak years,the upper part of the plateau area shows a negative height,and the lower layer shows an anticyclonic circulation.(2)The correlation analysis between the Tibetan Plateau summer monsoon index and the Tibetan Plateau heat source Q shows that the relationship between the index defined by Tang and the heat source is the best,and the correlation coefficient with the summer heat source reaches 0.3.The correlation coefficient of the summer monsoon index reached 0.36 in July.By analyzing the circulation background of atmospheric heat sources in the Tibetan Plateau,we can find that the positive and negative anomalous annual synthesis of the 200hPa geopotential height field has similar characteristics.The positive anomalous years show positive anomalies in the Tibet Plateau and negative anomalies in negative years.level.There is also a certain difference between the two:In the synthesis of the 200 hPa geopotential height field of the Tibet Plateau heat source,the positive and negative height centers in the-Tibet Plateau region are more southward than the summer monsoon in the Tibet Plateau.(3)The time period for the RCP4.5 scenario to reach a temperature increase of 1.5? is 2017-2036(Accurately reaches 1.5? for 2027).The time period for the RCP8.5 scenario to reach an increase of 1.5? is 2016-2030(Accurately reaches 1.5? for 2024).By comparing the plateau summer monsoon intensity under historical and different emission scenarios,it can be seen that the plateau summer monsoon intensity is increasing under the warming background,and the increase of monsoon intensity under high emission scenarios is even greater.There is a significant positive correlation between the thermal difference between the atmospheric heat source around the plateau and the atmospheric heat source of the plateau and the plateau summer monsoon.