Doppler radar study on the successive development of snowbands at a convergence line near the coastal region of Hokuriku District

摘要

During the field experiment of winter mesoscale convective systems over the Sea of Japan in 2001 (WMO-01), several snowbands associated with a cold front developed remarkably at 1030 km off the coast of Hokuriku district on 28 and 29 January 2001. Dual-Doppler radar analysis was made to investigate the mechanisms responsible for the successive development of the snowbands.Derived wind fields revealed that a mesoscale convergence line was formed between the prevailing westerly and shallow (similar to 1 km depth), cold southwesterly winds that blew from inland toward Toyama bay. As the downshear-tilting convective cells in the snowbands approached the convergence line, they became almost upright and their height increased from 4 km to 6similar to7 km. The edge of the southwesterly cold air temporarily became indistinct because of the entrainment of the air into the convective cells that developed aloft. However, the subsequent advection of the cold southwesterly reestablished the convergence line, and enabled the successive development of following snowbands.