26 December 2002
From the satellite data analysis, a researcher Youichi Tanimoto of Climate Variations Research Program, Frontier Research System for Global Change*, who is also an Associate Professor at Graduate School of Earth Environmental Science, Hokkaido University, and Professor Shang-Ping Xie and researcher Masami Nonaka, both from International Pacific Research Center, have discovered that the sea surface temperature distribution of Kuroshio current around southern coast of Japan has strong effects on the sea wind distribution. Also in the East China Sea and Yellow Sea, the sea bottom topography affects much its water temperature distributions in winter and even the development of low atmospheric pressure passing over Japan.
The discovery will be published on the December 28th issue of "Geophysical Research Letters", a publication of American Geophysical Union, as well as on the April 2003 issue of "Journal of Climate", a publication of American Meteorological Society.
* A joint project between National Space Development Agency of Japan and Japan Marine Science and Technology Center.
Kuroshio Current does not only have the large effect on the hydrological conditions around Japan, and is important for fishery and marine transportation, but also it affects large-scale climate around Japan, carrying much heat from the tropics. Although previously accepted theory assumes that the large-scale wind over Pacific Ocean drives the stream, it is also possible to assume that the stream drives the wind. However, the effect of Kuroshio Current on the wind had not been clearly understood. Also, the sea temperature distribution of East China Sea and Yellow Sea, which becomes upwind of Japan during winter, is thought to effect Japanese climate, but the mechanism of the distribution had competing theories and lacked the consensus.
ResultsThe analysis of the data from satellites, such as Tropical Rainfall Measuring Mission (TRMM), has lead to the discovery of the relationship that the change of Kuroshio Current near Southern Japanese Coast triggers a large sea surface temperature change and the fact that the wind is strong over the warm water and weak over the cold water (figures 1,2). It is presumable that this change in the wind has additional effects on the Kuroshio Current itself and the subsequent fishing ground. In the East China Sea and the Yellow Sea, the difference in the ocean depth causes the cooling effect by the winter time north wind to differ from place to place, which creates the unique temperature distribution that reflects the ocean bottom topography, and it also affects the sea surface wind and the cloud distribution (Attachment 1). In addition, numerical model showed that the temperature difference between warm Kuroshio Current in the west of Okinawa and the low water over continental shelf has a strong effect on the growth of cold pressure system.
The climate models used in the prediction of the El Nino phenomena and the global warming contain many uncertainties. Especially, the effect of the high to mid latitude ocean water on the climate is not well understood. By bringing these results into the climate model, it is possible to improve the accuracy of the climate change prediction.
Reference: Characteristic of satellite observation (Attachment 2)