Comparative Study of Climate Models(Section for Visiting Professors)

Research related to climate variation is being performed at many research institutes and universities around the world. The Section for Comparative Study of Climate Models invites professors and associate professors from abroad to exchange ideas on recent scientific results relating to climate modeling and analysis and to carry out cooperative studies. We intend to improve the climate models from various points of view and to increase our understanding of climate variations through these collaborations.

Climate models have been developed at many research institutes and universities around the world and used for various studies of climate variations such as global warming due to increased greenhouse gases. However, model results differ widely due to differences in model resolution and treatment of various processes such as clouds, radiation, boundary layers, land surface conditions and so on. In order to improve climate models, it is very important not only to validate model results with real observations, but also to check individual processes in the models by comparing different model results.

Figure 1 shows slightly different horizontal distributions of monthly averaged precipitation in the tropics for July obtained by two different cumulus parameterization schemes. It shows that the model precipitation is slightly different between the two. We plan to improve the individual schemes for the treatment of the physical and chemical processes included in the model through these comparative studies.

High quality global observational data on various parameters which make up the climate system are needed in order to validate the climate models. For this reason international observational experiments are very valuable. One such experiment, TOGA-COARE, was carried out during 1992-1993 over the tropical western Pacific, and a variety of observational data regarding the interaction between atmosphere and ocean were obtained. Figure 2 shows time-height cross sections of east-west wind and water-vapor content near the equator during 11-27, November, 1992 observed by the research vessel "Hakuho-maru", Ocean Research Institute, University of Tokyo. Variations in east-west winds in the lower troposphere below about 4 km with a period of 4-5 days can be seen, probably due to the passage of disturbances. It is interesting to note that dry air penetrates into the lower troposphere at around 2 km height for 13-15 November and for 25-26 November. Analyses of TOGA-COARE data are currently being done by a large number of researchers in Japan and abroad.

WOCE (World Ocean Circulation Experiment) is currently being carried out to clarify the features of world ocean circulations. GEWEX (Global Water and Energy Experiment) will start in the late 1990's to understand the global water and energy cycles. Moreover, Japan is proposing GAME (GEWEX Asian Monsoon Experiment) to examine the important role of the Asian Monsoon in global water and energy cycles. Our Center will participate actively in these international observational programs and work together with foreign scientists.