Interannual Summer Temperature Variations over Japan and Their Relation to Large-Scale Atmospheric Circulation Field

Abstract

Dominant modes of surface air temperature (SAT) interannual variations in Japanese summer climate are detected by a rotated empirical orthogonal function analysis, and statistical relations between the dominant SAT modes and atmospheric circulation are investigated by regression analyses. Relations to the large-scale atmospheric circulation patterns that had been already known, are also examined. As a result, two dominant modes are detected that correspond well to the large-scale atmospheric circulation patterns, and relations between the SAT modes and atmospheric circulation can be interpreted statistically. The first mode represents SAT variations in the central part of Japan. The second mode represents those in the northern part. Greater than 75% of SAT variations can be explained by these two leading modes. The first mode accompanies variations of sunshine duration, and is related with the strength of the Tibetan High. The second mode involves quasi-six-year periodicity, and accompanies an appearance of the shallow type of the Okhotsk High, with the cold northeasterly winds that is related with the convective activity around the Philippine Islands.