Structure and maintenance process of stationary double snowbands along the coastal region

Abstract

When a cold air outbreak occurred over the Sea of Japan, double snowbands stayed along the coastal region of the Kanazawa Plain from 15 to 16 January 2001: Snowband 1 on the seaward side, and Snowband 2 on the landward side. Their structures are studied mainly using Doppler and dual-polarization radars, and their maintenance processes are discussed. The double snowbands were maintained for about 20 hours. Snowband 1 had a stronger reflectivity and a higher echo top than Snowband 2. The cells in Snowband 2 were generated in the weak echo extending from Snowband 1 toward the land. Around the snowbands, a southeasterly land breeze, with a thickness of 400 m was present. A convergence between the land breeze and the northwesterly monsoon wind formed a strong updraft. Convective cells in Snowband 1 developed in association with the strong updraft. In Snowband 2, a weak convergence produced a weak updraft. The dual-polarization radar data showed that Snowband 1 was composed of spherical graupels, including conical ones. On the other hand, flat-shaped snow crystals were converted to snow aggregates along the trajectory of the particles within Snowband 2. Graupels were seen in the pictures taken below Snowband 1, while only snow aggregates were observed below Snowband 2. These facts indicate that the strong updraft at the land-breeze front contributed to the formation of graupels through the riming process in Snowband 1, on the other hand, snow aggregates developed through the deposition and aggregation processes in the weak updraft in Snowband 2. Some snow crystals, which contributed to the formation of snow aggregates in Snowband 2, were supplied from Snowband 1. © 2005, Meteorological Society of Japan.