Abstract
There was a snowfall in the SeoulGyeonggi region for two days, from 1 to 2 March, 2005. The snowfall occurred by snow clouds which had been developed over Yellow Sea entering into the region. The clouds had an organized pattern of cloud street, wind-parallel cloud bands. The kinematic characteristics of snow clouds were investigated using Terminal Doppler Weather Radar(TDWR) observation data, atmospheric soundings, NOAA satellite infrared images, and weather charts. Our synoptic analysis shows that a trough was separated from the cyclone in the central region of China due to an expansion of Siberian high, and then during the passage of the trough over the Yellow Sea, the snow clouds were developed. The cloud street was observed in infrared satellite images and was also recognized on the PPIs of radar reflectivity. The kinematic characteristics of wind field under the snow clouds development were analyzed by Volume Velocity Processing(VVP) method(Waldteufel and Corbin, 1979). The wind field analysis indicates that maxima of convergence and vertical velocity were 2.0${\times}$$10^{-4}s^{-1}$ and 16 $cms^{-1}$, respectively. And there was cold advection in atmospheric layer of surface$\sim$1.3km height. The maximum advection of -0.42$^{\circ}C$ per hour occurred from 0430LST to 0800LST on 2 March. The present analysis shows that the cloud street was developed by the inflection point instability under the stable atmospheric condition. The bands extended over 100km in length and the inter-band spacing was about 9km. The inflection point height was changed with the wind directions. The inflection point height was about 1.3km, and the vertical wind shear had maximum value(2.1${\times}$$10^{-2}$-2.4${\times}$$10^{-2}s^{-1}$) at inflection point height. The present observational study suggests that the development of cloud street is possible even under the stable atmospheric condition through the inflection point instability.