Climatic Characteristics Of Sea Fog Frequency Over The Northern Atlantic

In this master thesis, the latest International Comprehensive Ocean-Atmosphere Data Set (ICOADS) is utilized to analyze the spatial and temporal distribution of sea fog frequency over the Northern Atlantic and the eastern coast of North America. By using different grid accuracy (2°×2°over the Northern Atlantic, 1°×1°over the eastern coast of North America), monthly "relative frequency" of sea fog occurrence is calculated in two regions aforementioned. Meanwhile, the meteorological and oceanographic factors which are significantly related to the process of sea fog are statistically analyzed100-year ICOADS data from 1909 to 2008 is used to analyze the distribution patterns of sea fog. For the Northern Atlantic, sea fog mainly occurs over middle and high latitude. Sea fog frequency over the western region is higher than that over the eastern region. Sea fog frequently occurs near Long Island to the east of Newfoundland which has a maximum value greater than 30%. Sea Fog also occurs over the region near the east of Iceland and Norwegian Sea, but there is almost no sea fog over the low latitude of the ocean. Sea fog over the Northern Atlantic mainly occurs from April to August and attains the peak value in July. In the eastern coast of the Northern America, the area affected by sea fog is from the north of New York to the Labrador Sea. There are two maximum value centers located over the regions south of Nova Scotia and the east of Newfoundland Island, respectively, and one minimum value center over the Gulf of St. Lawrence. Sea fog season usually starts from April and ends in August. The maximum sea fog frequency usually occurs in the period from June to July.The spatial and temporal distributions of sea fog frequency along five major sailing routes (New York-London, Miami-London, Gibraltar-New York, Miami-Boston, Miami-Halifax) are analyzed, aiming at choosing the best paths in order for ships to avoid entering into the heavy sea fog regions.By using 27-year ICOADS data from 1982 to 2008, some important meteorological and oceanographic factors which are closely related to sea fog occurrence, for instance wind direction, wind speed, the difference between the air temperature and dew point temperature, sea surface temperature, are examined. For the sea area from the Long Island to the east of Newfoundland, and the sea area from the Iceland to British Islands, the S-SW wind with speed of about 8 m/s are dominated when the atmospheric visibility is less than 1000 m,. The suitable Sea Surface Temperature(SST) ranges from 5℃to 15℃and no fog occurs when SST is greater than 25℃near Newfoundland and 20℃near Iceland. The difference between air temperature and sea surface temperature usually ranges within -1℃to 3℃, suggesting that the advection cooling is dominated for the sea fog formation.