ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 37 Issue 11 > 2011,37(11):1343-1351. DOI:10.7519/j.issn.1000-0526.2011.11.003 Prev Next
A Dynamic Diagnosis of the 091031 First Snowfall in Beijing with Some New Intensive Soundings
- Article
- Figures
- Metrics
- Preview PDF
- Reference
- Related
- Cited by
- Materials
Abstract:
Usually, the time of the first snowfall in Beijing is about on November 28. During the period of the nighttime of October 31, 2009 to daytime of November 1, 2009, there was a weather process which never occurs over the past 22 years. In this process, the precipitation firstly acted as rain, then converted to sleet and finally in the form of snow. Analysis shows that, over the north region of the Yellow River in middle and east parts of North China, the lower troposphere was controlled by northwest flows for 6 hours even to 12 hours before this snowfall, thus the transport and accumulation of water vapor were not obvious. This snowfall process is infrequent for Beijing in such a dry condition in October. The dynamic calculation and analysis of this snowfall process were conducted with the MICAPS data of CMA, windprofiler, radiometric and surface automatic weather station observations in Beijing. The result shows that, the dynamic action of the southward outbreak of strong cold air from Baikal Lake in upper troposphere was the main reason for this snowfall process. A 500 hPa positive vorticity advection area, a middle and upper tropospheric divergence center and a middle and lower tropospheric convergence center were vertically distributed over Beijing, which support the favorable environment for vertical motion; the coactions of the warm and humid sourheast winds near the ground in piedmonts and plains, the cold and humid east winds in the boundary layer, the west winds in tropospheric bottom, which were seen in windprofiler, and the topographic effect in western Beijing will generate an uplift and local convection to enhance snowfall in southwest Beijing. This paper proposes a conceptual model about how the wind distribution in windprofiler in the piedmonts and plains of Beijing and the topographic effect will generate the uplift motion and local convection. The water vapor condition of this snowfall is from the shortterm growth of humidity by nearsurface southerly winds and southeast winds, and the local moisture convergence in the lower troposphere.
Keywords:
Project Supported:
Clc Number:
Mobile website
