ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 37 Issue 11 > 2011,37(11):1380-1388. DOI:10.7519/j.issn.1000-0526.2011.11.008 Prev Next
Numerical Simulation and Analysis on a Heavy Snow of ReturnFlow Events in Beijing
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Abstract:
The typical returnflow events with heavy snow during 2-3 January, 2010 by using Beijing local highresolution rapid update cycle mesoscale model system (BJRUC) are simulated. The characteristics of synoptic system in each layer and key snowfall factor are analyzed. The results show that the BJRUC model can well simulate the snowfall distribution, position and time change, and the main situations of heavy snowfall which are caused by the cold air returnflow in the lowlevel， and the 850-700 hPa layer lowvortex system. But the snowfall center has still some deficiency. When the vertical ascending motion is produced in lower atmosphere by the cold returnflow encountering terrain, the snowfall is not high. During the snowfall, the dynamic lifting which is caused by the cold returnflow combining with the ascending motion of the foreside of low vortex, forms a deeply and violent ascending motion, that is the key factor to cause the heavy snow. The durative and cold returnflow with high humidity transports water vapor in the lower atmosphere. The humidity in the lowermid troposphere is increased by the southwestern air flow. The returnflow increases thickness of wetlayer, reaching above 600 hPa. It plays an important role in producing the heavy snow. The start and intensity of snow fall are related to the moment of the direction change to southern wind and the south wind speed.
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