Synoptic climatology of winter daily temperature extremes in Sapporo, northern Japan

Abstract

Extreme winter daily temperature is an important parameter for determining winter precipitation. This study used a principal component analysis and k-means clustering to characterize the circulation patterns of extreme daily temperatures for 19 winter seasons in Sapporo, Hokkaido, Japan. Climatological anomaly maps were constructed for sea level pressure (SLP) and the 500-hPa geopotential height for the identified minimum (Tmin10; 239 days) and maximum (Tmax90; 236 days) daily temperature extremes. The Tmax90 SLP anomaly pattern was the opposite (west–east orientation) of the Tmin10 pattern. The circulation patterns that predominantly contributed to winter rainfall were derived from cyclones over the Sea of Japan via instability created by abundant heat and moisture over the ocean and a strong positive 500-hPa height anomaly over Hokkaido.