Climate Changes in the 21st Century Over the Asia-Pacific Region
Simulated by the NCAR CSM and PCM
Aiguo Dai, G. A. Meehl, W. M. Washington, and T. M. L. Wigley
National Center for Atmospheric Research
P. O. Box 3000
Boulder, CO 80307
The Climate System Model (CSM) and the Parallel Climate Model (PCM), two coupled
global climate models without flux adjustments recently developed at NCAR, were
used to simulate the 20th century climate using historical greenhouse gas and
sulfate aerosol forcing. These simulations were extended through the 21st
century under two newly developed scenarios,a business-as-usual case (BAU,
CO2 = 710 ppmv in 2100) and a CO2 stabilization case
(STA550, CO2 = 540 ppmv in 2100). In this paper, we analyze the
simulated changes in temperature, precipitation, and soil moisture over the
Asia-Pacific region (10oN-60oN, 55oE-155o
E), with a focus on the East Asian summer monsoon rainfall and climate changes
over the upper basin of Yangtze River.
Under the BAU scenario, both the models produce surface warming of about
3-5oC in winter and 2-3oC in summer over most Asia. Under
the STA550 scenario, the warming is reduced by 0.5-1.0oC in winter
and by 0.5oC in summer. The warming is fairly uniform at the low
latitudes and does not induce significant changes in the zonal mean Hadley
circulation over the Asia-Pacific region. While the BAU simulated regional
precipitation changes are noisy, the PCM ensemble mean precipitation shows
10-30% increases north of ~30oN and ~10% decreases south of
~30oN over the Asia-Pacific region in winter and 10-20% increases in
summer precipitation over most of the region. Soil moisture changes are small
over most Asia. The CSM simulation suggest ~30% increases in river runoff into
the Three Gorges Dam, but the PCM ensemble simulations show small changes in the
runoff.
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Hongjun Zhang:
zhangho@ucar.edu