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Inter-comparison of Asian monsoon simulated by RCMs in Phase II of
RMIP for Asia
Jinming Feng, Congbin Fu, Shuyu Wang, Jianping Tang, D. Lee, Y. Sato, H. Kato, J. Mcgregor et al.
Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China. fengjm@tea.ac.cn
1. Abstract
In phase II of the Regional Climate Model Inter-comparison
Project (RMIP) for Asia, the regional climate has been
simulated for July 1988 through December 1998 by five
regional climate models and one global variable resolution
model. Comparison of the 10-year simulated precipitation
with the observations was carried out. The results show that
most models have the capacity to reproduce the basic spatial
pattern of precipitation for Asia, and the main rainbelt can
be reproduced by most models, but there are distinctions in
the location and the intensity. Most models overestimate the
precipitation over most continental regions. Interannual
variability of the precipitation can also be basically
simulated, while differences exist between various models
and the observations. The biases in the stream field are
important reasons behind the simulation errors of the
Regional Climate Models (RCMs). The cumulus scheme
and land surface process have large influences on the
precipitation simulation. Generally, the Grell cumulus
scheme produces more precipitation than the Kuo-Anthes
scheme.
2. Design of experiments
In order to understand the performance of RCMs on
simulating Asian, especially East Asian climate, the
Regional Climate Model Inter-comparison Project (RMIP)
for Asia was launched by START Regional Center for
Temperate East Asia in 2000 (Fu et al., 2005). There are six
participant models in phase II of RMIP, of which five are
RCMs and one is a global variable-resolution model. They
include: RIEMS (Fu et al., 2000), NJU MM5, MRI
JSM_BAIM, RegCM2b, SNU RCM, CSIRO CCAM. The
experiment domain is the same as phase I, which contains a
large part of the Asian continent, western Pacific, Bay of
Bengal and the South China Sea (Fig. 1). The horizontal
resolution of the models is 60 km, with a 151×111 grid in
the east-west and north-south directions. The simulation
period is from July 1988 to December 1998. The driving
fields come from NCEP-II reanalysis data, with a 15-grid
buffer zone. The NCAR terrain data are used in the model
integration with a horizontal resolution of 0.5°×0.5°, in
addition to satellite land surface data supplied by NASA.
The same driving field, topography, land surface vegetation,
simulation domain and horizontal resolution ensure the
comparability of the simulation results.
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45°E 60°E 75°E 90°E 105°E120°E 135°E 150°E 165°E
Fig.1. Simulation domain for RMIP
3. Some results
The driving fields come from the NCEP-II reanalysis data,
but these reanalysis data have some biases. The spatial
distribution of the NCEP-II bias has some similarities with
the results of most models over the continental region,
such as the positive bias over most areas of Mongolia and
the southwest of China, and the negative bias over the
north of India, etc. Because of the few observation stations
in Northwest China and the Tibetan Plateau, the observed
data used to validate the models almost come from the
CRU precipitation data, so a larger bias may exist. Hence,
maybe the biases of the large-scale forcing fields and the
deficiency of the validation data are one of the possible
reasons for the biases of the simulation.
In summer, the southeastern and southwestern monsoons
prevail in the East Asian continent. The strong summer
monsoon transports the abundant vapor northwardly from
the Bay of Bengal and West Pacific, thereby generating a
large amount of precipitation in South China, Changjiang-
Huaihe and later in North China. For the summer monsoon
current located to the south of 30ºN, it is underestimated
by MRI compared to the NCEP-II data. So the
precipitation simulated by MRI is much smaller in
summer, while it is greater in the other models. The
summer monsoon current simulated by RIEMS is much
stronger and the region of strong monsoon current is
extended further northward. This is the main reason that
RIEMS simulates much more precipitation in the summer.
The summer monsoon current simulated by SNU is close
to NCEP-II, and the bias of the simulated precipitation is
smaller relatively. Hence, the biases of the monsoon
current are important reasons for the simulation errors of
RCMs.
4. Some conclusions
Most models overestimate the precipitation in most
continental regions. The seasonal variation of precipitation
can be simulated, but there are large differences in the
regional precipitation among the models.
The biases of the stream fields are important reasons
behind the simulation errors of RCMs. Also, the deviation
of the large-scale driving fields may be one reason for the
simulation biases. The cumulus parameterization scheme
and land surface process have a large influence on the
precipitation simulation.
Most models can basically simulate the trend of the
interannual variation of precipitation, but there are large
differences in the magnitude of precipitation among the
models.
References
Fu, C. B., and coauthors, Regional Climate Model
Intercomparison Project for Asia. Bull. Amer. Meteor.
Soc., 86, 257-266., 2005.
Fu Congbin, Wei Heilin, and Qian Yun, Documentation
on a Regional Integrated Environment Model System
(RIEMS version 1). TEACOM Science Report No.1,
START Regional Committee for Temperate East Asia,
Beijing, China, 1-26, 2000.