Sensitivity of Snowfall Characteristics to Meteorological Conditions in the Yeongdong Region of Korea

This study investigates the characteristics of cold clouds and snowfall in both the Yeongdong coastal and mountainous regions under different meteorological conditions based on the integration of numerical modeling and three-hourly rawinsonde observations with snow crystal photographs for a snowfall event that occurred on 29−30 January 2016.We found that rimed particles predominantly observed turned into dendrite particles in the latter period of the episode when the 850 hPa temperature decreased at the coastal site,whereas the snow crystal habits at the mountainous site were largely needle or rimed needle.Rawinsonde soundings showed a well-defined,two-layered cloud structure along with distinctive wind-directional shear,and an inversion in the equivalent potential temperature above the low-level cloud layer.The first experiment with a decrease in lower-layer temperature showed that the low-level cloud thickness was reduced to less than 1.5 km,and the accumulated precipitation was decreased by 87%compared with the control experiment.The difference in precipitation amount between the single-layered experiment and control experiment(two-layered)was not so significant to attribute it to the effect of the seeder−feeder mechanism.The precipitation in the last experiment by weakening winddirectional shear was increased by 1.4 times greater than the control experiment specifically at the coastal site,with graupel particles accounting for the highest proportion(~62%).The current results would improve snowfall forecasts in complicated geographical environments such as Yeongdong in terms of snow crystal habit as well as snowfall amount in both time and space domains.

Characteristics of environmental factors associated with typhoon Kongrey(1825) over the Eastern Coastal Region of Korea

In this study,the characteristics of environmental factors associated with typhoon Kongrey were examined using radiosonde,wind-profiler,radar,and Automated Surface Observing System(ASOS)data in Uljin,which is located the eastern coast of Korea.The radiosonde data were obtained from intensive observation between 1500 LST 5 to 0000 LST 7 October 2018.Environmental factors such as Total Precipitable Water(TPW)and Strom Relative Environmental Helicity(SREH)were selected to examine their relations to typhoon-accompanied precipitation.The TPW peak with 60.54 mm appeared at 1200 LST 6 October,which is 6 h after the peak of typhoon precipitation.It was found that the TPW variation is largely associated with the effect of water vapor supply from the typhoon with nearest proximity to Uljin at 1500 LST 6 October.Mean SREH,which indicates mechanical instability,was 761 m2 s-2 during the period in which typhoon precipitation occurred.These environments would provide a good condition for the development of super-cell storms,causing heavy precipitation associated with typhoon.In addition,it was found that the correlation coefficient between SREH and typhoon rainfall is 0.8(p-value=0.02).