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Simulation of Asian monsoon climate by RMIP Models
Shuyu Wang, Jinming Feng, Zhe Xiong and Congbing Fu
Institute of Atmospheric Physics, CAS, Beijing 100029, China, wsy@tea.ac.cn
1. Introduction
Regional climate model has shown its great abilities to add
regional details in climate and climate change signals, which
are forced by mesco-scale forcings such as topography,
inland water body, the coastline, land use/land cover
changes, ect. However, more systematic evaluation of RCM
to adequately assess its performance and uncertainty in
reproducing the regional climate information is required. To
fully assess the regional climate model’s advantages and
disadvantages in simulating the Asian monsoonal climate,
and to provide better confidence in projecting regional
climate change, the Regional Climate Model
Intercomparison Project (RMIP) for East Asia has been
established to study the performance of an ensemble of
regional climate models (RCMs) when simulating Asian
climate. Started in 2000, RMIP is under the joint support of
Asia-Pacific Network for Global Change Research (APN),
the Global Change System for Analysis, Research and
Training (START), the Chinese Academy of Sciences
(CAS), and other national projects. RMIP seeks to improve
further the RCM simulations of East Asian climate by
evaluating their strengths and weaknesses in a common
framework (Fu et al., 2000).
equatorial flow, the Indian South West Monsoon flow,
ITCZ over South China Sea and the tropical western
Pacific, the western Pacific subtropical High and tropical
easterly flow and the Meiyu Front zones.
As a weak East Asian Monsoon year of 1998, the weak
monsoon circulation produces too much precipitation over
Yangtze River valley, which caused severe flooding. Most
models captured the extreme heavy rainfall in 1998,
though the models simulated intensities are different from
that of observation (Fig.1). The results also show that
models tend to overestimate the precipitation at the higher
latitude.
RMIP are carried out to improve RCMs simulation of East
Asian climate by evaluating their strengths and weaknesses
in a common framework. The specific objectives of RMIP
are: (1) to assess the current status of East Asian regional
climate simulation; (2) to provide a scientific basis for
further RCM improvement; (3) to provide scenarios of East
Asian regional climate change in the 21 st century based on
an ensemble of RCMs that are nested with GCMs.
A two-phase simulation program has been conducted to
meet these objectives.
Phase-one, the 18-month simulation (March 1997- August
1998) covers a full annual cycle and contains two climatic
extremes, i.e., the East Asian drought in summer 1997 and
the floods in the Yangtze and Songhua River Valleys of
China, as well as in Korea and Japan during summer 1998.
The tasks of phase-one are to examine the models’
capabilities to reproduce the seasonal cycle of East Asian
Monsoon Climate, and to capture the basic character of two
extreme climatic events. Totally nine models, including
eight RCMs and one conformal-cubic Atmospheric Model,
from five countries have taken part into the RMIP’s phase
one simulation. 1998 is the weak summer monsoon year,
and the results phase one are used to examine the models’
performances on simulating this abnormal monsoon year.
Phase-two is 10-year continuous simulation (January 1989 -
December 1998) was conducted to assess the models’
abilities to reproduce the statistical behavior of the average
Asian model climate.
2. RMIP models’ simulation of weak monsoon
year of 1998
The main components of East Asian Summer Monsoon
System includes the Australian cold anticyclone, the cross
Figure 1. the total summer precipitation (mm) by
RMIP Models.
3. Mean Monsoon Climate by RMIP models
The East Asian summer monsoon begins following the
onset of the South and East Asia monsoons. Fig.2 shows
the spatial distribution of 10-year mean summer total
precipitation from RMIP Phase-Two results. All models
reproduce the main monsoon rainfall center over Yangtze
Valley of China, but either overestimate or underestimate
the rainfall amount compared with observations.