The Character, Mechanisms And Interannual Variation Of China Inshore Sea Fog

This paper summarized basic rules of China inshore sea fog using 37 coastal Chinese weather stations' foggy data, reanalysis data of NCEP and so on;Using correlative, compositive and regressive method, hydrology-weather conditions and main weather types which cause and maintain China inshore sea fog were studied, interannual variation, long term trend and their affecting factors of China inshore sea fog were also discussed. Main conclusions are as follows:1. There are distinct seasonal, territorial characteristics in China inshore sea fog: (1) The fog appears mainly from February to July, and April has the highest frequency, which reaches 4.1 days a month on average in the whole sea area. Since January, fog area moves from south to north along with the time. The spatio-temporal rule of the process numbers of sea fog is in accordance with foggy days'.(2) The annual trend of foggy hours is similar to foggy days', but the former has a bigger change rate than the latter in the transition of fog season to non-fog season;The most foggy hours focus on the south inshore of the Shandong peninsula represented by Chengshantou.(3) The summer has the most foggy days, but the foggy area is relative smaller;The spring has fewer foggy days than the summer, but the foggy area is the largest;The fall has the smallest number of foggy days and the foggy area is quite small;The winter has more foggy days and larger foggy area comparing to the fall.2. The formation and vanishing of sea fog along Chinese coasts do not have obvious rule as terrestrial fog. In general, area influenced strongly by terrestrial weather show larger daily variation in contrast to area under strong influence of marine weather;in the same oceanic-continental condition, the coasts along Chinese southern sea show larger daily variation comparing to the northern sea.3. On average, The duration of China inshore sea fog process is long in the winter and the spring, and short in the summer and the fall, The regional difference is less distinct than the foggy days' and foggy hours', and the long duration foggy processes concentrate on the coast of southern Shandong peninsula;The more consecutive foggy days region concentrate on the coast of southern Shandong peninsula and the coast of southern Zhejiang.4. The formation of sea fog is a result of coeffect of multi-factors, including lower SST, positive difference of air temperature and SST, bigger humidity, appropriate southward wind and the situation of height field of higher at east side and lower at west side of China inshore.5. The main weather situations which form and maintain China inshore sea fog are as follows:(1) Type of higher west and lower east, subtropical high edge, low pressure foreside and equal pressure field at Bohai sea and Yellow sea.(2) Type of cyclone, southwest low pressure and cold front at east China sea.(3) Type of cold front or stationary front foreside, in-sea high pressure and southwest low pressure at north part of south China sea.6. There is great difference among each sea area in interannual variation of China inshore sea fog, the maximum annual foggy day appears later in Chinese northern sea comparing to the southern sea, which is mainly caused by interannual variation of northwest Pacific Ocean subtropical high. The annual foggy day of the whole China sea area show a descent trend from 1964 to 2000, preceding Pacific Ocean subtropical high, Pacific Ocean polar vortex and Asia meridional cell are all indicative to forecast of China inshore sea fog.