1. Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA;
2. Frontier Research Center for Global Change, Japan Agency for Marine-Earth Science and Technology Center, Yokohama, 236, Japan;
3. International Research Institute for Climate Prediction, Palisades, NY 10964, USA;
4. Department of Earth and Planetary Science, University of Tokyo, Tokyo, 113, Japan;
5. Liberal Arts Education Center, Tokai University, Hiratsuka, 259, Japan;
6. NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA;
7. Japan Meteorological Agency, Tokyo, 100, Japan