Decadal change of the East Asian summer monsoon and its related surface temperature in Asia-Pacific during 1880–2004

The East Asian summer monsoon(EASM)and its related change of surface temperature in the past century were not clearly addressed due to absence of atmospheric reanalysis data before 1948.On the benchmark of station-observed sea level pressure(SLP)in China,we utilized multiple SLP datasets and evaluated their qualities in measuring the SLP-based EASM index(EASMI).It is found that the EASMI based on the SLP of the Hadley center version 2(HadSLP2)has shown the best performance on the interannual and decadal time scales.Instead of showing a linear weakening trend pointed out by the previous study,the EASMI has likely exhibited the decadal variability,characterized by weakened trends during 1880–1906,1921–1936,and 1960–2004,and with enhanced trends during 1906–1921 and 1936–1960,respectively.Corresponding to the weakened and enhanced periods of EASMI since the 1920s,the surface air temperature(SAT)index(SATI)averaged in eastern China has likely shown a warming and a cooling trend,respectively.However,the decadal abrupt transitions between the two indices do not occur concurrently,which results in a weak correlation between two indices on the decadal time scale.Further analysis indicates that there are four key regions where the SAT is significantly correlated with the EASMI,suggesting the joint impact of surface temperature in Asia-Pacific on the EASM during 1880–2004.In which,the decadal change of SAT near the Lake Baikal plays an important role in the linear trends of the EASM before and after 1960.