[Objective] The research aimed to study the physical mechanism of snowstorm which was generated by the south cyclone. [Method] By using the routine meteorological observation data, satellite data and MM5 mode output d...[Objective] The research aimed to study the physical mechanism of snowstorm which was generated by the south cyclone. [Method] By using the routine meteorological observation data, satellite data and MM5 mode output data, the snowstorm weather in the east of Heilongjiang Province during March 4-6, 2007 was analyzed. The physical mechanism of snowstorm which was generated by the south cyclone was discussed. [Result] Jianghuai cyclone advanced northward to generate the snowstorm. In the middle and high latitudes, the good cold air must coordinate with it. Meanwhile, the south cyclone provided the good high temperature condition and the rich water vapor condition for the snowstorm generation. The snowstorm generation must have the close coordination of airflows in the high and low levels, and the strong convergence ascending movement was generated. The vertical movement made that the atmospheric energy could be transformed. When the snowstorm was generated, there was the strong vertical ascending movement in the high altitude. The snowstorm falling zone was in the north side of big value zone. The variation of TBB cloud top temperature intensity as the time had the good guidance role for forecasting the starting time of strong snowfall. The convergence center of water vapor flux divergence and the zone where the temperature drew point difference in 925 hPa layer ≤ 4 ℃ had the good corresponding relationships with the snowstorm falling zone and the snowfall strong center. It provided the good reference index for forecasting the falling zone and strong center of snowstorm. Under the restriction of moist potential vorticity conservation, for the leaning of θe surface, the atmospheric horizontal wind was vertical, or the wet baroclinicity increased, which could cause the significant development of vertical vorticity. The bigger θe surface leaning was, the stronger the cyclonic vorticity was. It was easy to cause the strong precipitation weather. When the high-altitude dry cold air invaded and glided along θe ridg展开更多
In January 2008, South China experienced extremely low temperatures, heavy snowstorms, and severe frosts (2008 Frost Disaster, for short), which led to (partial) failures of observations from ground stations and groun...In January 2008, South China experienced extremely low temperatures, heavy snowstorms, and severe frosts (2008 Frost Disaster, for short), which led to (partial) failures of observations from ground stations and ground radars resulting in a lack of necessary emergency information. To compensate for the failure of ground observations and to provide timely disaster information, the National Satellite Meteorological Center of China (NSMC) established a snow storm monitoring system for the 2008 Frost Disaster, which was based on the WRF Three Dimension Variational Assimilation and Forecast system (with NOAH as the land surface sub-process model) cooperatively developed by NSMC and the National Center for Atmospheric Research (NCAR), US. This system made full use of ATOVS and NCEP data to provide estimates of snow water equivalent every 6 hours during the storm. In this study, the ATOVS assimilation based snowstorm monitoring scheme was explored in detail, while the modeled results with and without ATOVS assimilation were compared against related observations. Results showed that the coupling of ATOVS assimilation into the proposed monitoring system evidently delineates weather characteristics of the snowstorm process more accurately, and demonstrated the feasibility of the system for snowstorm monitoring and forecasting. Through theoretical analyses and case discussion, this study proposes a reliable and practicable scheme to provide timely and accurate information on snow spatial distribution and temporal development for disaster mitigation, and illustrates a new application of ATOVS data.展开更多
文摘[Objective] The research aimed to study the physical mechanism of snowstorm which was generated by the south cyclone. [Method] By using the routine meteorological observation data, satellite data and MM5 mode output data, the snowstorm weather in the east of Heilongjiang Province during March 4-6, 2007 was analyzed. The physical mechanism of snowstorm which was generated by the south cyclone was discussed. [Result] Jianghuai cyclone advanced northward to generate the snowstorm. In the middle and high latitudes, the good cold air must coordinate with it. Meanwhile, the south cyclone provided the good high temperature condition and the rich water vapor condition for the snowstorm generation. The snowstorm generation must have the close coordination of airflows in the high and low levels, and the strong convergence ascending movement was generated. The vertical movement made that the atmospheric energy could be transformed. When the snowstorm was generated, there was the strong vertical ascending movement in the high altitude. The snowstorm falling zone was in the north side of big value zone. The variation of TBB cloud top temperature intensity as the time had the good guidance role for forecasting the starting time of strong snowfall. The convergence center of water vapor flux divergence and the zone where the temperature drew point difference in 925 hPa layer ≤ 4 ℃ had the good corresponding relationships with the snowstorm falling zone and the snowfall strong center. It provided the good reference index for forecasting the falling zone and strong center of snowstorm. Under the restriction of moist potential vorticity conservation, for the leaning of θe surface, the atmospheric horizontal wind was vertical, or the wet baroclinicity increased, which could cause the significant development of vertical vorticity. The bigger θe surface leaning was, the stronger the cyclonic vorticity was. It was easy to cause the strong precipitation weather. When the high-altitude dry cold air invaded and glided along θe ridg
基金supported by National Natural Science Foundation of China (Grant Nos.40705037 and 40801175)the Open Fund by Numerical Model Innovation Base of China Meteorological Administration (Agreement 2006-12)the R & D Special Fund for Public Welfare Industry (Meteorology GYHY(QX)2007-6-9)
文摘In January 2008, South China experienced extremely low temperatures, heavy snowstorms, and severe frosts (2008 Frost Disaster, for short), which led to (partial) failures of observations from ground stations and ground radars resulting in a lack of necessary emergency information. To compensate for the failure of ground observations and to provide timely disaster information, the National Satellite Meteorological Center of China (NSMC) established a snow storm monitoring system for the 2008 Frost Disaster, which was based on the WRF Three Dimension Variational Assimilation and Forecast system (with NOAH as the land surface sub-process model) cooperatively developed by NSMC and the National Center for Atmospheric Research (NCAR), US. This system made full use of ATOVS and NCEP data to provide estimates of snow water equivalent every 6 hours during the storm. In this study, the ATOVS assimilation based snowstorm monitoring scheme was explored in detail, while the modeled results with and without ATOVS assimilation were compared against related observations. Results showed that the coupling of ATOVS assimilation into the proposed monitoring system evidently delineates weather characteristics of the snowstorm process more accurately, and demonstrated the feasibility of the system for snowstorm monitoring and forecasting. Through theoretical analyses and case discussion, this study proposes a reliable and practicable scheme to provide timely and accurate information on snow spatial distribution and temporal development for disaster mitigation, and illustrates a new application of ATOVS data.
