Dynamic Character Analysis Of A MesoScale Snow Storm Event In Shandong Peninsula

In Shandong Peninsula, the snow storm in 3-4 January 2003 was a typical meso-scale weather process,but it was misforcasted by weather numerical-model(T213 et.)and operational weather service.On the Peninsula,there are WNW-ESE direction Laishan Mountain(~37.2?N),which is a low-altitude(500m ASL) ridge,and Bohai sea and North Yellow sea in the north of the Peninsula . By analyzing the satellite cloud maps,observation data and simulation results with MM5v3.6,it is found that when very cold airmass flows out over the sea ,it was strongly heated and moistened, relative humity got higher and higher ,at last the airmass was nearly sturatde, then weak conditional symmetric instability was seen near the surface ,thus shallow convection appeared. The simulated results showed that in the favorable large-scale air circulation, both thermodynamic instability and dynamic forcing by the Laishan Mountains, produce meso-scale coast front and meso-scale gravity wave .and the mesoscale system excit the release of the energy of the symmetric instability.As a result .shallow convection was seen and thus an obvious increace of snowfall intensity was observed .In the papar, the maintenance and generation of the gravity wave is discussed.