Numerical Simulation And Mesoscale Characteristics Analysis About A Snow Storm In Shandong Peninsula In December 2005

A severe snow storm occurred on 3 December 2005 in Shandong Peninsula is simulated with a mesoscale model MM5V3.6, and detailed diagnostic analyses are performed upon the mesoscale gravity-wave (MGW) event. This process of heavy snowfall is a typical mesoscale snow storm process. The nonlinear balance equation (NBE) is evaluated for its usefulness in the diagnostic of the flow imbalance, and analyses indicates that the important role of the geostrophic adjustment and topographic forcing in gravity-wave event of the snow storm. Through a series of sensitivity experiments, further illustrating the impacts of the land-sea thermal difference, and the topographic forcing.Research shows that The MGW's wavelength is about 120 km, and the propagation speed is about 7 m·s^-1. In the favorable large-scale circulation situation, The Taihang Mountains and the flow imbalance are important to initiate the MGW, the thermal force of the ocean in winter is the key mechanism in resulting the local snow storm. The NBE diagnostic shows clear evidence of the MGW initiation region and propagation direction. An analyses in wave structure and maintaining mechanism suggests that the MGW in this snow storm satisfies the necessary conditions for wave ducting and Wave-CISK. This complex sequence of nonlinear interactions produced a long-lived, large-amplitude gravity-wave that created hazardous winter weather. The results of Land-sea sensitivity experiment shows that the Bohai Sea supports the development of the fluctuations; the terrain sensitivity experiment about Shandong Peninsula shows that the special topographic features of Shandong Peninsula induce the heavy snowfall in the northern coastal and weak snowfall in the southern region of Shandong Peninsula.