Abstract
This study evaluates variability of East Asian Monsoon simulated by 24 coupled general circulation models (GCMs) participating in Coupled Model Inter-comparison Project 3 (CMIP3). Fifty years (1950 - 1999) of each model's twentieth-century climate simulation are analyzed and compared with observed data. Both East Asian Summer Monsoon (EASM) and East Asian Winter Monsoon (EAWM) are considered. Suitable indices are selected to analyze EASM and EAWM. The Wang-Fan index, associated with 850 hPa circulation pattern and tripole rainfall pattern are considered to analyze EASM. ICHENW, associated with 850 hPa circulation pattern, IGONGDY, associated with Siberian High, and ISUNBM, associated with 500 hPa East Asian trough are considered for analysis of EAWM. Inter-decadal and inter-annual variability of the EASM and EAWM are major focus of this study.The results indicate that, amplitude of inter-annual component EASM becomes larger after 1980's. The decadal component shows, weakening trend and switching from positive monsoon phase to negative monsoon phase in mid-80s for both EASM and EAWM. The simulated composite differences between weak and strong monsoon decades by models with above mentioned characteristics are compared with observation for further evaluation. The EASM weakening is associated with weaker southwesterly and stronger anti-cyclonic pattern over Western North Pacific and results in more rainfall in south and north China, Korea, Japan and less rainfall in central China. The EAWM weakening is associated with weakening of Siberian High and temperature rise over East Asia. EASM and EAWM matrices are constructed according to the relative merits of GCMs.
Highlights
In preparation for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), more than a dozen international climate modeling centers have conducted a comprehensive set of long-term simulations of climate during the twentieth century and various climate scenarios in the twenty-first century (IPCC 2007) under the coordination of the Coupled Model Inter-comparison Project 3 (CMIP3)
In order to project the future characteristics of the East Asian monsoon, it is necessary to validate the capability of CMIP3 general circulation models (GCMs) in quantifying the variability in the East Asian monsoon
This study is based on the 20th century simulations (20C3M) of 24 GCMs provided by CMIP3, which is the main basis for the AR4 (IPCC 2007)
Summary
In preparation for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), more than a dozen international climate modeling centers have conducted a comprehensive set of long-term simulations of climate during the twentieth century and various climate scenarios in the twenty-first century (IPCC 2007) under the coordination of the Coupled Model Inter-comparison Project 3 (CMIP3). Several studies have considered the validation of CMIP3 models in simulating the East Asian monsoon. In order to project the future characteristics of the East Asian monsoon, it is necessary to validate the capability of CMIP3 GCMs in quantifying the variability in the East Asian monsoon. This issue has been relatively unexplored in previous studies. The present study includes a comprehensive assessment of the relative merits of CMIP3 models in simulating the East Asian summer and winter monsoon (EASM and EAWM) variability. A large number of summer and winter monsoon indices have been proposed Some of these indices are adopted in this study for model validation
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