Intercomparison of the climatological variations of Asian summer monsoon precipitation simulated by 10 GCMs


I.-S. Kang 1, K. Jin 1, B. Wang 2, K.-M. Lau 3, J. Shukla 4,

V. Krishnamurthy 4, S. D. Schubert 5, D. E. Wailser 6, W. F. Stern 7,

A. Kitoh 8, G. A. Meehl 9 , M. Kanamitsu 10, V. Ya. Galin 11,

V. Satyan 12, C.-K. Park13, and Y. Liu 14


1 School of Earth and Environment Sciences, Seoul National University, Seoul, Korea

2 International Pacific Research Center, University of Hawaii, Hawaii, U.S.A.

3 Climate and Radiation Branch, NASA/Goddard Space Flight Center, Greenbelt, Maryland, U.S.A.

4 Center for Ocean–Land–Atmosphere Studies, Institute of Global Environment and Society, Inc., Calverton, Maryland, U.S.A.

5 Data Assimilation Office, NASA/GSFC, Greenbelt, Maryland, U.S.A.

6 Institute for Terrestrial and Planetary Atmospheres, State University of New York, Stony Brook, New York, U.S.A.

7 Geophysical Fluid Dynamics Laboratory/NOAA, Princeton University, Princeton, N.J., U.S.A.

8 Meteorological Research Institute, Tsukuba, Ibaraki, Japan

9 National Center for Atmospheric Research, Boulder, Colorado, U.S.A.

10 National Centers for Environmental Prediction, Camp Springs, Maryland, U.S.A.

11 Institute of Numerical Mathematics of Russian Academy of Sciences, Moscow, Russia

12 Indian Institute of Tropical Meteorology, Pune, India

13 Climate Prediction Division, Korea Meteorological Administration, Seoul, Korea

14 Institute of Atmospheric Physics, Beijing, People’s Republic of China




Corresponding author address: In-Sik Kang, School of Earth Environment Sciences, Seoul National University, Seoul, 151-742, Korea   Email:

Tel: 82-2-880-6718,  Fax: 82-2-885-7357



This paper assesses the overall performance of state-of-the-art atmospheric GCMs in simulating the climatological variations of summer monsoon rainfall over the Asian-Western Pacific region and the systematic errors that are common to a group of GCMs. The GCM data utilized are obtained from 10 GCM groups participated in the CLIVAR/Monsoon GCM Intercomparison Project. The model composite shows that the overall spatial pattern of summer monsoon rainfall is similar to the observed, although the western Pacific rainfall is relatively weak. For the simulated precipitation over the western Pacific, the models can be classified into two categories. The first category of models simulates the precipitation more confined to the equatorial region and weaker precipitation in the subtropical western Pacific compared to the observed. The second category of models simulates large precipitation in the subtropical western Pacific but the region is shifted to the north by 5-10 degree. None of the models realistically reproduce the observed Mei-yu rain band in the region from the East China Sea to the mid Pacific. Most of the models produce a rain band in the continental side of East Asia.


The climatological variations of simulated summer rainfall are examined in terms of their amplitude and their principal EOF modes. All models simulate larger amplitudes of the climatological seasonal variation of Indian summer monsoon than the observed, whereas most models simulate smaller amplitudes in the western Pacific. The 10  model composite produces four leading EOF modes over the Asian-Western Pacific region, which are remarkably similar to the observed counterparts. The first and second eigenmodes, respectively, represent the smoothed seasonal march of broad scale monsoon and the onsets of the Indian and East Asian summer monsoon. The third and fourth modes relate to the climatological intraseasonal oscillation (CISO). In contrast to the model composite, several models fail to reproduce the first principal mode, and most models do not reproduce the observed modes higher than the second. The CISO of precipitation is also examined over the Indian monsoon and the East Asia-western Pacific monsoon regions separately.