2011-9-13 By Xiu-Qun YANG Nanjing University 1

Xiuqun Yangxqyang@nju.edu.cn

Institute for Climate and Global Change Research, School of Atmospheric Sciences,

Nanjing University, Nanjing 210093, CHINA

Decadal Change in East Asian Monsoon Climate System: Natural Variability vs Anthropogenic Forcing

International Conference on Science and Technology for Sustainability 2011Building from Regional to Global Sustainability-Visions from Asia

September 14-16, 2011, Kyoto International Conference Center

Schematic illustrating progression from initial value problems with dailyweather forecasts at one end, and multidecadal to century projections as a

forced boundary condition problem at the other, with seasonal and decadalprediction in between

Meehl, et al. BAMS, 2009

Why emphasize the decadal change?

Natural signature vs. anthropogenic forcing

2011-9-13 By Xiu-Qun YANG Nanjing University 3

What is the observed decadal change in East Asian monsoon climate system ?

Can such a decadal change be considered as natural variability (say, the PDO’s impact)?

What is the role of increased CO2 and aerosols?

Summary

Issues

Climatological East Asian Summer Monsoon

Winter(DJF)

Summer(JJA)

Interdecadal variabilities of 9-yr running averaged precipitation in eastern China since 1900

Northern China

Yangtze River valley

Southern China

Sun, 2006

1980s

EASM Index: Standardized 850hPa and surface v-component (110 º- 125 ºE，20 º- 40 ºN)

NCEP/NCAR

ERA-40

Observed

1979-92

1993-04

1951-78

Decadal weakening of East Asian summer monsoon and southward shift of rainbelt in China

Wang, Ding, Jhun 2006 GRL

Decadal change of EASM rainfall (1948-2004) over whole East Asian domain

Post-1976 minus Pre-1976