Inter-annual variability of surface cyclone tracks, atmospheric circulation patterns, and precipitation patterns, in winter

Abstract

Three major teleconnection patterns prevailing at 500 hPa height, e.g., North Atlantic Oscillation (NAO), Pacific-North American (PNA) and Western Pacific (WP) patterns, are investigated in the northern Winter season associated with cyclone tracks and precipitation patterns. Cyclone position and tracks, objectively analyzed using NCAR Sea Level Pressure Grids (1964–1990) and ECMWF 1000 hPa height grids (1980–1990), are composited in reference to the extreme appearance of positive or negative teleconnection patterns around the Atlantic and Pacific. The correlations between the teleconnections and the inter-annual variability of precipitation are also investigated. Significant changes of major cyclone routes are commonly and clearly found in the two data sets as follows. In case of ±NAO patterns, major zonal cyclone tracks fluctuate meridionally, and cyclones tend to move eastward in the middle parts of North Atlantic, or they direct northeastward along the northwestern Atlantic to reach the Norwegian Sea. Significant variations of precipitation associated with these changes of cyclone tracks are found in southwestern and northwestern parts of the west coast of Europe. In the case of dominant ±PNA patterns, cyclones tend to direct eastward within 40°–50°N over the North Pacific and turn north to migrate to the Gulf of Alaska to Bristol Bay, or they move northeastward along the northwestern edge of Pacific to migrate to the Bering Sea or strike on the east coast of Canada. The former pattern corresponds to a strengthening of the eastern part of the Aleutian low, and the latter pattern provides the positive correlation with precipitation on the east coast of Japan and a part of the west coast of Canada. Dominant iWP patterns are responsible for the meridional fluctuations of apparent zonal distribution of cyclone tracks with its strike of a SSW-NNE direction over the Northern Pacific. The northward shift of this distribution provides the increase of the precipitation amount in the southwestern islands and central Pacific regions of Japan.