Characteristics of heavy snowfall for the past decade in the Yeongdong region of Korea

The Yeongdong region has various meteorological phenomenon by virtue of complicated geographical characteristics with high Taeback Mountains running from the north to the south and an adjacent East Sea to the east. 17 snowfall episodes have been investigated for the past ten years in order to study its association with low-level stability and air-sea temperature difference over the East Sea. The basic mechanism to initiate snowfall around Yeongdong seems to be similar to that of lake-effect snowstorms around Great Lakes in the United States (Kristovich et al., 2003). Difference of equivalent potential temperature between 850 hPa and surface as well as difference between air and sea temperatures altogether gradually began to increase in the pre-snowfall period and reached their maximum values in the course of the period, whose air- sea temperature difference and snowfall intensity in case of the heavy snowfall events are almost larger than 20°C and 6 times greater than the weak snowfall events. Interestingly, snowfall appeared to begin in case of an air-sea temperature difference exceeding over 15°C. The results demonstrate that an instability-induced moisture supply to the lower atmosphere from the East sea, being cooled and saturated in the lower layer, East Sea-Effect Snowfall (SES), would make a low-level ice cloud which eventually moves inland by the easterly flow. Sometimes geographic induced convergence along the coastal line leads to a heavy snowstorm. The vertical profiles of sounding and ceilometer measurement show that low-level clouds existed below 2~3km with cloud base less than 1km, where northeasterly and northerly winds were consistent. Interestingly integrated water vapor obtained from the MWR and GNSS began to exceed above 10mm around 15 ~ 16hrs before the snowfall. There was a distinctive time lag between water vapor, liquid water path, and snowfall. Snow density of Gangneung (GN: a coastal site) and Daegwallyeong (DGR: a mountainous site) was examined for the past three decades (1981~2012). The snow density of GN (geometric mean: 89.3 kg/m3) is overall higher than DGR (65.1 kg/m3). This year, record-high 2m accumulated snowfall amount was observed during 6-14 February 2014 with a 9-day duration, when 35 vertical soundings has been launched and also snow particles has been taken on the ground in Gangneung in the name of ESSAY2014. Various forms of snow crystals were present such as stellar sector, spherical graupel, conical graupel, aggregation of rimed dendrite, etc in the cloud base lower than 1km and thickness less than 2km. During the snowfall period snowfall intensity sometimes was 2cm/hr. The snow density of GN and DGR are 94.3 kg/m3 and 64.5 kg/m3 during the ESSAY2014, similar to that of the past three decades. Detailed analysis of snowfall characteristics in Yeongdong will be discussed along with various forms of beautiful snow crystals at the meeting.