南京市能见度变化趋势及其影响因素

Variation Trends of Atmospheric Visibility and Its Influence Factors in Nanjing

利用1980~2013年南京国家基本气象站的地面常规气象要素和能见度观测资料,剔除相对湿度和天气现象对能见度的影响,采用等级分析法、＂非常好＂能见度出现频率法、累积百分率法、Ridit中值分析等方法,分析了南京地区大气能见度的年际和季节变化趋势;并利用偏相关分析法分析了能见度与气温、气压、平均风速和相对湿度的相关关系。结果表明,能见度有明显日变化和季节变化,一天中,8：00最差,14：00最好;一年之中,能见度夏季最好,冬季最差。1980~1984年南京能见度呈上升趋势,1985~2004年呈波动下降趋势,2005~2013年则呈缓慢上升趋势;＂较差＂和＂一般＂能见度出现频率呈现上升趋势,＂较好＂能见度出现频率则明显下降。能见度水平逐年代下降但降幅减小;能见度等级分布的季节差异逐年代减小。能见度与平均风速呈正相关,与相对湿度呈负相关。由于南京地区气候条件的影响,能见度与气压和气温均存在季节性差异,能见度与气压在冬季呈较好的正相关,与气温夏季呈正相关、冬季呈负相关。

To well understand the trends of visibility in Nanjing during 1980~2013, relative humidity and other whether phenomenon were considered,and the following methods were used,namely,grades analysis,frequency of ＂very good＂ visibility,cumulative percentiles,ridit analysis and etc.,furthermore,partial correlation analysis was used to see correlation between visibility and some meteorological elements. The results showed that during one day, visibility was worst at 8：00 and best at 14：00,while it was best in summer and worst in winter during one year. And visibility has increased during 1980 ~1984,but declined during 1985~2004,and later went back slowly during 2005 ~2013. The frequency of ＂poor＂ and ＂common＂ visibility went up while ＂better＂ visibility declined dramatically. In addition, visibility was declining with decades along with the decreasing amplitude getting smaller. Furthermore,the visibility trades had distribution differences between four seasons diminished with decades. And visibility showed a positive correlation with average wind speed,and a negative correlation with relative humidity.Because of the local weather conditions in Nanjing,the correlation between visibility,pressure and temperature had seasonal differences,which showed that visibility showed a well positive correlation with pressure in winter and temperature in summer,and a negative correlation with temperature in winter.