GLOBAL CLIMATE CHANGE RESEARCH AT CCSR/UNIV. OF TOKYO Akimasa Sumi* Center for Climate System Research, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan Tel: (81 3) 5453 3951 Fax: (81 3) 5453 3964 Email:

ABSTRACT The Center for Climate System Research (CCSR) was established in 1991 to develop a climate model and promote research relating to the global climate change. We could succeed in development of the 1st generation climate model, and several research topics have been investigated by using the model. Research activities of the CCSR are summarized by Sumi (2000) and a few topics are presented in the following. RESEARCH TOPICS RELATING TO THE GLOBAL CLIMATE CHANGE 1. Global warming prediction Study

Global warming prediction study has been conducted as a central theme of our center. First, we conducted the experiments by using the green-house-gas-only model. Then, we conducted another experiment by using the revised model with an indirected effect of aerosol (Emori et al., 1999) and an indirect/direct effect of aerosol for IPCC 4 SRES scenario (Nozawa et al., 2000). These results will be included in the IPCC TAR. 2. Decadal climatic variability

Decadal climate variability is a hot-topic in the climate research. Watanabe and Kimoto (1999) have been investigating this topic and they proposed a mechanism of the coupling between the tropics and the mid-latitude. 3. Asia monsoon variability

Asian Monsoon is very interesting and important research topic for us. Especially, the strong El-Nino happened in 1997 and a heavy summer rainfall over the Yantzen River in China was observed in 1998. El-Nino effect on the Indian summer rainfall in 1997 was investigated by Shen and Kimoto (1999) and the 1998 summer rainfall case was examined by Kimoto et al. (1999). A strong influence of SST over the Indian Ocean was found in these studies MODEL DEVELOPMENT AND FUTURE OUTLOOK The 1st generation climate model was parallelized and can be run in T21, and T42 with NIES (National Institute of Environmental Studies). AGCM can be run in T106. Besides this, modelling for atmospheric chemistry has been intensively conducted. (1) The first stage of the stratospheric chemistry modelling has been done and numerical experiments for ozone depletion and effect of the Pinatubo eruption are being conduct. (2) The modelling for the tropospheric chemistry is being developed. For the OGCM, a new 1 x 1 degree model has been developed with the bottom boundary current, which gives good results.

We are now developing a new version of the Climate model, where no use of a flux correction is used. The details are as below: 1. Atmosphere

CCSR/NIES AGCM (paralleled code) is used. Direct effect of aerosol is included in the radiation. Indirect effect of aerosol for clouds is included as an option. A new surface model (MATSIRO) will be used. Gird advection scheme for moisture is used. 2. Ocean

CCSR OGCM will be used, which has a rigid lid,and parallelized. Advection scheme is UTOPIA and isopycnal diffusion is included. Gent-McWilliams diffusion and Noh and Kim mixed layer are optional. 3. Sea-ice

Simplified Hiber-type model will be used. We are pursuing a next-generation climate model, where high resolution AGCM and OGCM will be used. Resolution may be T106-T213 for AGCM and 1.0-0.1 for OGCM depending on availability of computer time. At the same time, physical processes should be updated with the finer resolution. Parametarization schemes for convection, radiation and boundary layer physics will be developed by comparing the results of the meso scale model with the large-scale model.

REFERENCES Emori, S., Nozawa, T., Abe-ouchi, A., Numaguti, A. and Nakajima, T. 1999. Coupled ocean-atmosphere model experiments of future climate change with an explicit treatment of sulfate aerosol scattering. J. Met. Soc. Japan 77: 1299-1307. Kimoto, M., Shen, X., Sumi, A., Numaguti, A. and Matsumoto, J. 1999. Simulation of the 1988 East Asian Summer Monsoon by the CCSR/NIES AGCM. CGER. Super Computer Activitiy report Vol. 8 (available from CGER/NIES in Tsukuba, Japan). Nozawa, T., Abe-ouchi, A. and Kimoto, M. 2000. Global warming experiments for IPCC-SRES, to be submitted. Shen, X. and Kimoto, M. 1999. Influence of El Nino on the 1997 Indian Summer Monsoon. J. Met. Soc. Japan 77: 1023-1037. Sumi, A. 2000. Climate Simulation Studies at CCSR. General Circulation Model Development, ed. by D.A. Randall, Academic Press, 489-507.

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