| Strong wind (particularly strong crosswind) is one of main meteorological disasters that influence the safe driving of the vehicle on expressways. In order to improve forecast accuracy and reduce the loss,it’s very import to comprehensive comprehend the occurrence regularity, formation and maintain mechanism of strong wind and strong crosswind.1. In this paper, in this paper, the systematical observed data from the Automatic Monitoring System of Traffic Weather on the typical expressways in Jiangsu Province from 2012 to 2015 was used to analyze the temporal and spatial pattern of strong wind and strong crosswind. Consequently, the wind pressure on typical expressway in Jiangsu was classified to reveal the spatial distribution characteristics of wind pressure.The results showed as follows: (1)the daily and seasonal variation pattern of the strong crosswind similar to the pattern of the strong wind. The occurrence time sections of their highest frequency were 12:00 to 14:00 pm, the months of their highest frequency were July. (2) The highest frequency of strong windand strong crosswind all appear in Coastal expressway; the Suqian-Huaian-Yancheng expressway is the lowest. The frequency of the north wind was highest. The extreme strong wind direction with the highest frequency was 22.5°.(3)Except for the Suqian-Huaian-Yancheng Expressway in autumn, 2012,the monthly extreme strong wind speeds of all four expressways from 2012 to 2015 exceeded 10 m/s and their maximum value reached 22.6m/s. (4) considering comprehensively the factors of wind direction variation and wind speed variation,according from large to small the wind pressures were divided into 10 grads. Among the classification results of the wind pressure, the highest frequency of wind pressures was Coastal Expressway. (5)The geographical environment had the different impacts on the strong wind, strong crosswind and the wind pressure levels in the different sections of these expressways. Among them,the effects of the topographic relief, the distribution of water system, the distance from the sea were remarkable.2.Weather Research and Forecasting Model were used to the simulations and diagnostic analysis of a strong crosswind event caused by strong cold air during 9th to 10th, March in 2013. The results showed as follows: (1) the strong winds was appeared by strong cold air control the upper air and the cold anticyclone was developed and moved eastward (2) the effective coordination of divergence field at high and low level and the cold front crossing was one of the import reasons that this strong wind occurs. (3) the frontal gale was formed by the warm and cold drafts converge, The vehicle was more dangerous when the road is wet and slippery. (4)CAPE was low and CIN was high, The convective exchange is small in this strong wind process. (5) there was a small range of cold and warm advection interaction in the middle of strong wind. The underlying atmosphere was controlled by cold advection and the upper atmosphere was controlled by warm advection after the cold front, the atmosphere was relatively stable and maintained.3 .Weather Research and Forecasting Model were used to the simulations and diagnostic analysis of a strong crosswind event caused by Typhoon during 7th to 10th, August in 2012. The results showed as follows: (1) the simulation results of strong wind are very satisfactory and the process mainly affects southern Jiangsu. (2)The convergence divergence value of typhoon center is very high when Typhoon landing. And the value was reduced as Typhoon moves. (3) the water vapor under the 400hPa was abundant, the relative humidity was over 80%. The weakening of precipitation lags behind the wind.. (4) In the process of the typhoon, the high CAPE area represents the range of the rainstorm area in the future. The time variation of CAPE value can provide a good inspiration for the forecast of rainstorm.(5)According to the warm advection and the cold advection, the rising of the central air flow could be easily distinguished.4. Weather Research and Forecasting Model were used to the simulations and diagnostic analysis of a strong crosswind event caused by Typhoon during 31th, July in 2013, The results showed as follows: (1) The wind range is more dispersed,The simulation results are not good, but the correlation coefficient is still above 0.6. (2)the strong wind process occurred for lower level convergence and upper level divergence, the range of strong convective was small but had serious impact. (3) The vertical structure of water vapor is distributed in the upper and lower humidity,which was easy to form convective unstable stratification.the strong convective weather was triggered. (4) High CAPE and low CIN provides a favorable energy environment, is an important condition caused by strong wind weather (5) Unstable stratification of cold air in the upper level and warm air in the lower level, promoted the formation of convective systems,and produced momentum transfer, the ground wind speed will be increased. |
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