The Band Structure of Snowfalls

Abstract

Horizontal distribution of the amounts of precipitation during local heavy snowfalls in the lower Ishikari Plain, Hokkaido, does show a band shape, its direction being from NW to SE or from W to E. In this paper, such a band is denominated as ″snowfall band ″. The first factor effective upon the occurrence of snowfall band in this area is the formation of cloudstreets in the northern area of the Sea of Japan. The formation of such cloudstreets can be explained as due to the convection in heated air flows with restoring force by the wind shear, as suggested by Kuettner. Some features of a snowfall band are described under four headings, i.e., a) synoptic situation and snowfall, b) cloudstreets, c) snow crystals, and d) colder air under clouds precipitating graupels.