Characteristics Analysis on a Snowstorm in Shandong Peninsula by Using Multiple Observation Data
Using multiple data of Doppler weather radar, windprofiling radar, automatic station, buoy station, conventional sounding and surface observation, the characteristics of occurrence and evolution of one snowstorm event in the east of Shandong Peninsula in December 2014 are analyzed. The results show that firstly, over the Bohai Sea, the 500 hPa temperature is -36℃ or so, the 850 hPa temperature is in the range of -18--16℃, the direction of the Bohai Sea surface wind is northwest and its velocity is more than 12 m·s-1 when the snowstorm occurred. The conventional sounding data show that the mixing layer is below 700 hPa and the atmosphere in the 1000-700 hPa mixing layer is almost saturated. The buoy station shows that the larger airsea temperature difference bewteen the Bohai Sea surface and 850 hPa, and the stronger coastal front in Shandong Peninsula are the critical causes for the snowstorm. Secondly, during the snowstorm, the radar reflectivity is between 30 and 45 dBz. The analysis on the radar echo vertical section of the reflectivity every 6 min reveals that a strong snow echo cell can maintain for one hour. The velocity of Doppler data shows that the distribution of heavy snow cells occurs in the east area of the conversence zone between NE and NW winds. The horizontal wind convergence of coldflow snowstorm mainly exists below 3 km. The wind profile radar data show that there is a lowlevel western breeze under 100 m before the formation of the snowband. The existence of weak northwestern wind in 150-700 m height and the convergence of lowlevel shear line are beneficial to strengthening the convection of snowstorm. When such weak northwestern wind layer disappears, the snowstorm ends.