Numerical Study Of Dynamical Mechanisms And Meso-scale Characters Of High Wind Events At The Bohai Sea And The Northern Yellow Sea In The Winter And The Spring

High wind events at the Bohai Sea and the northern Yellow Sea are severe weather phenomena, and have been paid close attention by meteorologists. For a long time, people have emphasized statistical analyses of data and diagnostic study of dynamical mechanisms for high wind events in order to find their disciplinarians, and great progress has been made, but the numerical simulation study of high wind events in the areas is still a few. In this paper, two cases of high wind events in 7-8 December of 2002 and 2-3 March of 2003 was simulated using PSU/NCAR model MM5. The simulated results were contrasted to the observed facts. Based on the simulated results, multi-scale interactions and evolvement of the meso-scale systems were emphatically studied to reveal the dynamical mechanisms of high wind events.The historical data of high wind events at the Bohai Sea and the northern Yellow sea in 1980-1999 was statistically analyzed to get the total survey. The results presented that the prevailing wind for high wind events is northerly in whiter. But both the northern high wind and the southern high wind exist in lately autumn and early spring.The weather circulation patterns for two cases were investigated. It is found that the Mongolia plateau was controlled by Mongolia cold high pressure, the low pressure center was situated in the southern Yellow Sea area, and the westerly flow laid in the upper troposphere. The stronger cold air in the winter could reach the northern seashore of the Bohai Sea and the northern Yellow Sea and produce a distinct sea-land temperature difference, but the sea-land temperature difference wasn't obvious because of the weaker cold air hi spring.The cases were simulated to find the energy sources of high wind events. The results of the first case show that the momentum of the upper air jet was transmitted to the northern seashore by the descending branch of the north-south directional vertical circulation cell. The vertical circulation cell included two centers which were separately situated in the boundary layer and the upper troposphere, and two centers were coupled to maintain the vertical ascending motion extending to the top of the troposphere at the southern Yellow Sea and the descending motion extending to the surface in the northeast china. Besides the momentum of the upper air jet for the second case, the northerly airflow in the front of the Mongolia cold high was also transported to the northern seashore along or across the Yanshan Mountain. Therefore, it can be said that the energy of high wind events at the Bohai Sea and the northernYellow Sea came from not only the northern airflow in the front of Mongolia cold high in the lower layer but also the descending airflow of the upper levels.The simulated results were investigated to find why the wind speed in the sea areas was strengthened. In the cases, the component in 345 degree of the pressure gradient force which oriented from north to south was bigger at the Bohai Sea and the northern Yellow Sea than the one in the other areas .The force pushed the air of great momentum at the northern seashore to move speedily into the sea areas. The ascending motion in the ascending branch of the vertical circulation cell pumped the air in circumference. The cold air at northern seashore moved speedily into the sea areas along the northern airflow in the bottom of the vertical circular cell. The air possessing great momentum along the northern seashore in winter and in spring was strengthened to move into the sea areas when it was both pushed by the pressure gradient force and attracted by the ascending motion of the vertical circulation cell.The sensitivity experiment on SST was implemented to understand the effect of sea-land temperament difference on the wind in the sea areas. It is found in the sensitivity experiment of 2癈 SST increase that the SLP were depressed and the sea surface wind speed was slightly raised. The increasing sea-land temperament difference in winter accelerated the high wind speed in the sea areas. However, the...