ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Doppler Radar Echo Features of Cold Airflow Snowstorms in Shandong Peninsula
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Abstract:
Several cold airflow snowstorms emerging in northern coast of Shandong Peninsula from 3 to 7 December 2005 and from 4 to 6 December 2008 were analyzed with Doppler radar data from Yantai and conventional observational data. The results show that the northeast cold vortex in mid troposphere influenced the Shandong Peninsula before and during the snowfall, respectively. Frequently strong cold air in the lower troposphere causes a great airsea temperature difference which is the main reason to induce thermal instability of atmosphere. The water vapor was transported to the snowfall area from the Bohai Sea and northern Huanghai Sea in the lower troposphere and boundary layer. Snowstorms occurred in updraft area with convergence in low troposphere and divergence in mid troposphere. Updraft layer is much more lower than summer heavy rain. The forming and maintaining of mesoscale coastal front along coast line of northern Shandong Peninsula played an important role in the genesis of snowstorms. Echo top and strong echo (above 30 dBz) height have good corresponding relationship with the lowlevel divergence, 0-2 km wind shear and airsea temperature difference. The strong convergence at 850 and 925 hPa, high 0-2 km shear and large lowlevel temperature difference were conducive to echo development. Doppler radar products show that the initial echo generated in southern Bohai Strait and the heavy snow band extended from Bohai Strait toward Shandong Peninsula, the composite reflectivity was about 25 to 35 dBz, echo top was about 3 km. In the velocity field, the coastal front along coast line of northern Shandong Peninsula was very obvious during the heavy snowfall. The swing of coastal front determines the heavy snowfall region which would be in the middle part of northern coast of Shandong Peninsula when the coastal front closes to the coast line, and would be in the east of northern coast of Shandong Peninsula when the coastal front is distant from the coast line.
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