A decomposition study of moisture transport divergence for inter-decadal change in East Asia summer rainfall during 1958–2001

Abstract

In this paper, we report on the results of an investigation into inter-decadal changes in moisture transport and divergence in East Asia for the two periods 1980–2001 and 1958–1979. The aim is to explore the mechanism of summer rainfall change in the region after abrupt changes. The relevant changes are calculated using ERA-40 daily reanalysis datasets. The results show that both stationary and transient eddy moisture transports to the Chinese mainland have declined since the abrupt change in atmospheric general circulation in the late 1970s, leading to more rainfall in South China and less in the North. The anomalous rainfall pattern coincides well with anomalous large-scale moisture divergence in the troposphere, of which stationary-wave or monsoon transport is dominant, in comparison with the contribution of the transient eddies. Furthermore, their divergences are found to be in opposite phases. In addition, meridional divergence is more important than its zonal counterpart, with an opposite phase in East Asia. Abnormal zonal moisture convergences appear in northwestern and northeastern parts of China, and are related to the excess rainfalls in these regions.An increase in transient eddy activity is one of the major mechanisms for excess rainfall in northern Xinjiang. Consequently, the anomalous rainfall pattern in East Asia results from a decline of the East Asian monsoon after the abrupt change, while the rainfall increase in northwestern China involves anomalies of both stationary waves and transient eddies on boreal westerly over the mid- and high latitudes.

Northwestward Migration of the Northern Edge of the East Asian Summer Monsoon During the Mid‐Pliocene Warm Period: Simulations and Reconstructions

“…A large northwestward shift (~300-500 km) of the northern edge of the EASM was The present northern edge of the EASM (Figure 3), characterized on the basis of CMAP precipitation data , shows a northeast-southwest trend similar to that in the preindustrial period, but its location migrates significantly southeastward compared with the preindustrial period. This is related to the southward displacement of the monsoon rainbelt observed during the last few decades due to the weakening of the EASM since the 1970s (Chase et al, 2003;Dai et al, 2012;Wang, 2001;Zhu et al, 2012). An additional cause is the summer "wet biases" over northern China in most of the coupled GCMs (Song & Zhou, 2014).…”

A novel method for analyzing the process of abrupt climate change

“…The abrupt climate change is described as the system transitioning from one stable state to another (Thom, 1972;Tong et al, 2014), i.e., the system swings between different states (Lorenz, 1976;Charney and DeVore, 1979), and it also has been verified in the climate system (Dai et al, 2012;Baker and Charlson, 1990;Wang et al, 2012;Alley et al, 2003;Xiao et al, 2011). Detection methods (Wan and Zhang, 2008;Fu and Wang, 1992;Yamamoto et al, 1986) have been greatly developed.…”

A novel method for analyzing the process of abrupt climate change

“…The climate system is complex and chaotic (Shi, 2009). The abrupt climate change is described as the system transitioning from one stable state to another (Thom, 1972;Tong et al, 2014), i.e., the system swings between different states (Lorenz, 1976;Charney and DeVore, 1979), and it also has been verified in the climate system (Dai et al, 2012;Baker and Charlson, 1990;Wang et al, 2012;Alley et al, 2003;Xiao et al, 2011). Detection methods (Wan and Zhang, 2008;Fu and Wang, 1992;Yamamoto et al, 1986) have been greatly developed.…”

“…Detection methods (Wan and Zhang, 2008;Fu and Wang, 1992;Yamamoto et al, 1986) have been greatly developed. Since the abrupt change theory was developed, increasing numbers of research (Goossens and Berger, 1986;Feng et al, 2008Feng et al, , 2011Stefan, 2002) studies have been launched. Most of the current detection methods judge the abrupt change as the changing of the statistics, such as the mean, variance and trend in different moments.…”