Observational Analysis And Numerical Simulation Of Cloud Characteristics Of The Bohai Sea-effect Snowstorms

In this study, twelve sea-effect snowstorm events occurred during2001to2010over the Bohai Sea were investigated. Amount of available observational data wereused, including stationary satellites （GMS-5, GOES-9, MTSAT） infrared data, cloudprofiling radar data of CloudSat satellite, FNL atmospheric reanalysis data and routineobservation data. Cloud evolution characteristics, sea-effect of the Bohai Sea, andvertical structure and compositions of snowstorm clouds were analyzed. The resultsillustrates that （1） the snowstorm clouds with different origins usually grow rapidlyover the Bohai Sea, and among the clouds there are dense clouds with horizontal scaleof100-300km in form of strips or a bulk, which is closely corresponding to thesnowfalls;（2） the snowstorm clouds during their initial stages can be divided intothree main types according to their formingpositions, and their movements depend onthe winds at850hPa height, and they develop under the unstable conditions thatresult from the heat and moisture exchange between the warm Bohai Sea and cold airabove it;（3） the height of mature sea-effect snowstorm clouds can reach4km or so,and its ice-water mixture content has an average value of about303mg·m^-3, and itsmaximum is about600mg· m-3and mainly distributes at2km height, andadditionally the maximum and average values of ice effective radius is about120μmand91μm, respectively. Additionally, one sea-effect snowstorm during4-6, Dec2008is conducted toinvestigate the influence factors using the WRF （Weather research and forecast）model and its three-dimensional variational data （3DVAR） assimilation system, and aseries of sensitivity experiments are applied. The results show that,（1） The vaporsources of sea-effect snowstorm are the Bohai Sea and the northern Yellow Sea, andthe amassed moist air over the Bohai Sea results from the cold front, which alsoprovides water vapor condition for cloud formation;（2） The main components ofsea-effect snowstorm cloud are ice, snow crystal and cloud water, and the top ofmature sea-effect snowstorm clouds can reach the height of5km. In the clouds, upperand below the height of2km are mainly ice crystal and snow crystal, cloud waterparticle, respectively. The cloud over the land formed by Taihang Mountain Leelow-voltage can promote the development of sea-effect snowstorm cloud with the"seeding-feedback" effect;（3） Bohai sea-effect provides suitable conditions for thesustainment and development of offshore convergence zone and snowstorm cloud,and more remarkable in the mature stage, the latent heat from the water vaporcondensation released improves the upward movement that promote the furtherdevelopment of cloud;（4） Proper terrain affects the development of the sea-effectsnowstorm. Taihang Mountain has significant influence on the Bohai convergencezone sustainment, the location and intensity of snowfall. Shandong Peninsula topographic has positive effects on the terrestrial snowfall distribution and amount,the snow falls10%-15%more compared with without topography.