虹桥机场能见度变化特征分析

分析了上海虹桥机场近18年(1987～2004年)能见度的年际变化、季节变化和日变化特征,发现虹桥机场能见度呈逐年下降趋势,但是能见度低于着陆标准的年发生频数却趋于减少,能见度的季节变化特征非常明显,夏季能见度最佳,冬季最差,出现低能见度的频数最高.一天中早晨4～8点的能见度最差,不利于飞机降落,而13～18点的能见度条件较好.小波分析的结果表明虹桥机场能见度变化以年周期和天气尺度周期(2.5～9.8天)最为显著,其次为准双周振荡(10～20天).一年中七八月份能见度最佳,一月能见度最差,转折点一般出现在春末夏初和秋末冬初.虹桥机场的能见度变化和大雾时数以及颗粒物关系密切,呈反位相变化特征.

ANALYSIS OF CHARACTERISTICS OF VISIBILITY VARIATION IN HONGQIAO AIRPORT

The annual,seasonal and daily variation of visibility was analyzed for Honqiao Airport from 1987 to 2004.Results showed that it decreased annually,and showed evident seasonal variation characteristics that visibility was the best in summer but worst in winter and low visibility mostly appeared in winter.The happening frequency of low visibility in Hongqiao Airport below aircraft landing standard decreased form 1987 to 2004.The best period in a day for airplane landing in Hongqiao airport is from 13:00 to 18:00(local time),while the worst is form 4:00 to 8:00.By wavelet transform analysis,it is found that visibility of Hongqiao Airport varies most significantly at annual and synoptic scales,and biweekly oscillation of 10-20-day period is also significant in summer.Visibility is the best in July and August but worst in January,with the turning point appearing at the end of spring to early summer,and the end of autumn to early winter.Visibility of Hongqiao Airport is closely correlated with fog hours and particles,and the variation between them is significantly negative.