基于小波变换的兰州市近十年空气污染指数变化

对兰州市近10年逐日空气污染指数的时间序列采用一维连续Morlet小波进行小波变换分析,研究了该市大气污染时间序列的多尺度变化特征、主周期和影响因素.结果表明:兰州市近10年空气污染指数在不同时问尺度上具有不同的"高一低"交替演化规律,且以300 d左右的变化为主周期,100 d左右的变化为次周期;受地形条件的影响,大...

Waveletanalysis of air pollution index changes in Lanzhou during the last decade

To demonstrate the multiscale variations,primary period and influencing factors in Lanzhou,we analyzed the time series of daily air pollution index during the last decade using the continuous Morlet wavelet transformation.The results showed that the air pollution index varied at diverse time-scales with periodic "high-low" fluctuations.The primary period of the daily variations was around 300 days and the secondary period was around 100 days.Due to topographical conditions,the air pollution was serious in winter and light in summer in most scales.Asecondary peak often occurred in spring which was affected by the sand-dust of the Gansu Corridor,the inflection points of serious to light pollution index each year were the vernal and autumnal equinoxes.The general status of air pollution tended to be better during the last 10 years in Lanzhou.However,the serious air pollution sometimes worsened with the rapid economic development.Therefore,wavelet analysis is an effective method to study the variation of time series of air pollution index,and the multiscale variations of other pollutants.