Analyses on characteristics of sea-land breeze over Donghai island of Zhanjiang in February of 2011

The average wind characteristics and sea-land breeze characteristics are analyzed by using the data of wind profiler during February 2011 on Donghai island of Zhanjiang.The results show that: the prevailing wind direction is northeasterly on Donghai island during February 2011 at an altitude of 150 m and the total frequency of occurrences of three directions E,ENE,NE is 66.6%,in contrast,the total frequency of occurrences of westerly is only 1%.There is an obvious difference of occurrence frequency between westerly winds and easterly winds.The hourly changes of average monthly wind speed is restricted to small range about 1 m/s from 1:00 to 15:00;and fluctuation becomes larger during 15:00 to 20:00,the maximal speed of 2.1 m/s appears at 16:00.In February,only two days meet the conditions of sea-land breeze.In sea-land breeze day,the common duration of sea breeze is from 13:00 to 20:00,lasting 7 h,and land breeze's common duration is from 2:00 to 7:00,lasting 5 h.The mean speed of land breeze is 0.8 m/s,which are smaller than 2.1 m/s of sea breeze.The vertical height of land breeze is about 1 200 m during the sea-land breeze day,which differs slightly from sea breeze.The wind speeds of both sea breeze and land breeze have the similar trends of increasing first and then decreasing with increasing altitude.The maximal wind speed of sea breeze appears at 750 m,and that of land breeze appears at 500 m.The sea breeze circulation is much stronger than land breeze in the region of 500 to 750 m height.The wind direction basically remains unchanged above 2 km and that is the large-scale uniform systematic west wind circulation.