Statistical Analyses of Snowfall Distribution in the Niigata Area and its Relationship to the Wind Distribution

Abstract

Analyses of precipitation amounts and surface winds observed at weather stations were conducted to investigate the effect of the topography on the snowfall distribution in Niigata. The topographic effect on the precipitation, particularly in the Niigata plain, has not been well discussed although Akiyama (1981a, 1981b) discussed the relationship between the snowfall distribution in Niigata and the synoptic scale condition. Using an empirical orthogonal function analysis, the winter precipitation distribution from 1988 to 2007 in Niigata was categorized as plain-type (P-type) and mountain-type (M-type). The P-type precipitation occurs under an upper trough over the Sea of Japan. The synoptic westerly wind, brought by the lower trough near the Japan Islands, and the deep convective mixed layer will be responsible for the precipitation in the plains of Niigata and Hokuriku. In addition, the Noto Peninsula and the mountain range to the east of the Hokuriku area seem to play an dynamical role in the precipitation in the Niigata plain. The M-type precipitation occurs under the upper trough over Japan. The synoptic scale condition brings northwesterly wind, which causes a topographic updraft at the mountain slope, resulting in precipitation dominated in the Niigata mountain range.