The Relationship between Tropical Convection and Winter Weather over Japan

Abstract

The relationship among tropical convection, the weather over Japan and the atmospheric circulation in the Northern Hemisphere during winter was statistically examined with the use of monthly mean temperature data over Japan, outgoing longwave radiation (OLR), 500mb geopotential heights and the sea level pressure. It was found that the temperature over Japan is highly correlated with convective activity around the Philippines, i.e., when the convection around the Plilippines is active, the temperature over Japan is lower than normal. Conversely, when the convection is inactive, temperatures over Japan are above normal.
Convective activity around the Philippines is also correlated with the Northern Hemisphere 500 mb geopotential heights, especially in the region of east Asia. When convective activity around the Philippines is strong, the 500mb heights around Japan are lower while those around Siberia are higher. Weak convection means higher 500mb heights over Japan and low heights over Siberia. Sea level pressure in the northwest Pacific east of Japan is lower while that in Siberia is higher for active convection cases. The converse is true for inactive conviction. Conclusions from these results indicate that for active convection the strength of the east Asia winter monsoon becomes stronger resulting in a cold winter over Japan. Inactive convection weakens the east Asian winter monsoon creating a warm Japanese winter.
The results of composite analyses show that the global height anomaly patterns such as the Eurasian and Pacific/North American patterns can be found more clearly in the active convection cases than in the inactive cases.