Winter weather in Japan controlled by large-scale atmospheric and small-scale oceanic phenomena

Wednesday, 17 December 2014
Yuta Ando1,2, Masayo Ogi3, Yoshihiro Tachibana1, Kunihiko Kodera1,4 and Koji Yamazaki2,5, (1)Mie University, Climate and Ecosystem Dynamics Division, Tsu, Japan, (2)NIPR National Institute of Polar Research, Arctic Environment Research Center, Tokyo, Japan, (3)University of Manitoba, Centre for Earth Observation Science, Winnipeg, MB, Canada, (4)Nagoya University, Solar-Terrestrial Environment Laboratory, Nagoya, Japan, (5)Hokkaido University, Graduate School of Environmental Earth Science, Sapporo, Japan
The important components of atmospheric circulation in the winter over the Northern Hemisphere are the Arctic Oscillation (AO) and Western Pacific (WP) pattern. Although in general negative AO and WP phases cause Siberia, East Asia, and Japan to be abnormally cold, Japan was relatively warm in October 2012 even though both the AO and WP were strongly negative. The temperature of the Sea of Japan reached a high in October 2012, and it was found that heating by these very warm waters, despite the small size of the Sea of Japan, overwhelmed the cooling effect of the strongly negative AO and WP in October. Linear regression analyses except the forcing of atmospheric circulations showed that Japan tends to be warm in years when the Sea of Japan is warm. Consequently, the temperature over Japan is statistically controlled by interannual variations of small-scale oceanic phenomena as well as by large-scale atmospheric patterns. Previous studies have ignored such small-scale oceanic influences on island temperatures.