Synoptic characteristics of heavy snowfalls at Busan of Korea caused by polar lows over the East/Japan Sea

The results of the present study prove that snowfall occurred due to the polar low (PL) in the Korean Peninsula and six cases of snowfall exceeding a snow depth of 2 cm over the past 16 years in Busan, South Korea. A strong northwesterly air current with a cold outbreak at the lower level passed through the Korean Peninsula and penetrated into the East/Japan Sea causing the generation and characteristics of a PL. However, a northeasterly air current due to a synoptic low (SL) in East Japan approached the east coast via the East/Japan Sea, which generated a wind field with mesoscale cyclonic circulation. In the center of this cyclone, a strong positive vorticity region was revealed from the lower level to the upper level. The air temperature in the center of the PL was warmer than the surrounding areas at the lower level. As the PL developed and the air temperature decreased, a rapid tropopause drop followed due to the effect of the cold core along with the cutoff low at the mid-level or the higher level. As a result, the stratification became more unstable. The PL moved into Busan as the cold core at the upper level rapidly moved to the lower latitudes, which formed an unstable region around Busan. The PL decayed because the cutoff low, the cold core, and the positive vorticity region at the upper level quickly moved to the east, thereby causing the stratification to stabilize. Also, because the approach to the Japanese Archipelago caused an increase in surface friction, the original structure could no longer be maintained.