The Study On Characteristics Of Sea-Land Breeze In Dalian Bay

In recent years, the problem of air pollution has been attached importance by all the world, and air quality is becoming the focus of people's attention with Dalian striving for internationalization and with the improvement of people's life. As a typical coastal city, its air pollution is affected greatly by Sea-Land breeze in Dalian.Macroscopical and detailed characteristics of Sea-Land breeze are analysed in this paper.As to macroscopical characteristics, the criterion of Sea-Land breeze Day in Dalian has been established according to the geographical position of Dalian Weather Station and the definition of Sea-Land breeze. Then the data from 1996 to 2001 collected by Dalian Weather Station is analyzed. The results indicate: (1) The appearance frequency of Sea-Land breeze Day is higher in Autumn and Winter; (2) The speed of sea breeze is stronger in Spring and Winter; (3) The average initial time of sea breeze is at about 11 o'clock and its speed is 3.47m/s. 5-6 hours later, the speed achieves maximum with 6.11m/s. At last, sea breeze turns to land breeze at 0 o'clock with 3.30m/s; (4) The yearly initial direction of sea breeze is WNW and NW, while the maximum direction is North.The experiment of low altitude exploration with Base-line windfmging in north coast of Dalian Bay has been carried out in order to study the detailed characteristics of Sea-Land breeze from May 7 to May 18, 2006. The time of observation is 2:00,5:00, 8:00, 11:00, 14:00,17:00, 20:00 and 23:00(lack 2:00, 5:00 and 23:00 in some days). Detailed characteristics is analyzed according to what has been observed. The results indicate: (1) The wind direction tends to change reversely at a height of 600m in the period of sea breeze, while the height is 450m in period of land breeze; (2) Wind speed increases quickly with the height less than 150m in the period of sea breeze while it increases placidly in the period of land breeze; (3) There is a layer with comparatively stable temperature below 400m, which suppresses the diffusion of pollutants; (4) According to the observation, inversion mainly appears in the region close to the ground, with a height about 150m in average in Dalian Bay; (5) The diffusional ability of atmosphere is higher in the afternoon than forenoon, and achieves its maximum at 12-14 o'clock for the pollution diffusivity.