Rapid increase of explosive cyclone activity over the midwinter North 1 Pacific in the late 1980 s 2 3

Akira Kuwano-Yoshida, Satoru Okajima, Hisashi Nakamura. 4 a Shirahama Oceanographic Observatory, Disaster Prevention Research Institute, Kyoto University, Shirahama, 5 Japan 6 b Shionomisaki Wind Effect Laboratory, Disaster Prevention Research Institute, Kyoto University, Kushimoto, 7 Japan 8 c Application Laboratory, Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan 9 d Climate Science Research Laboratory, Research Center for Advanced Science and Technology, The University 10 of Tokyo, Tokyo, Japan 11 12