The Two-dimensional Numerical Experiments And Forecast Of Seafog

Seafog is a hazard phenomena resulting from air-sea interaction that has significant influences on many aspects such as navigation, fishery work, harbor activity, plants growing near the sea shore, as well as the health for the mankind. So the related study is always an issue getting high attentions for many countries by seashore. In this thesis, after a systematic overview to the influence of seafog, the basic character of its occurrence near the sea of China, as well as studies on it, the formation mechanism of the seafog is preliminary investigated by using a two-dimentional model and the statistical prediction model is done for the seafog appearing costal region of Fujian Province during the Spring.What the roles of advection, turbulence and radiation processes take on the formation of seafog is a key for us to understand the seafog formation mechanism. Such issue is investigated in this thesis, based on an equation of relative humidity and a two-dimensional numerical model. It is shown that the main "promotion force" is longwave radiation cooling. The turbulence process cools the lower layer atmosphere at the initial stage of the advection process but turn to warm as time elapse (warm means not benefit for the formation of seafog). Turbulence and radiation exhibit opposite sign of influences for the lower layer atmosphere (the same sign occurs only at the earlier stage of the process of seafog formation), but the magnitudes of them are the same order; for the upper atmosphere, the effect of turbulence and that of radiation have the same sign, but radiation process dominates. Turbulence and radiation are the main factors determining whether seafog can be formed or not, the direct effect of advection is relatively small. The magnitudes of influence of advection, turbulence, and radiation (and the whole of them) decrease with time. The roles of wind and sea surface temperature on the effects of advection, turbulence and radiation, as well as on the formation of seafog are also investigated.The methods of Discriminant Analysis and Regression Estimation of Event Probability (REEP) are used to forecast the seafog occurring around the coastal region of Fujian Province during the Spring. The choice of factors used is based on the study of the mechanism of seafog formation and from the work experiences in forecast. A satisfactory result is got. What's more,since the forecast process is a conventional one, it plays a very important role in forecast.The above study will provide a better understanding to the occurrence character of seafog, as well as the occurring conditions of it and the mechanism involved in.