城市边界层动量和保守物通量的特征

利用2005年1-5月北京325 m气象塔47 m高度的湍流脉动资料(风速、温度、水汽和CO2),对城市边界层冠层内的湍流运动统计特征(相似关系、高阶矩、通量和谱等)进行了分析。其中,谱分析的结果表明,城市冠层内稳定度对湍流谱的影响比较小,而水平风速的影响比较大。因此,速度和温度的相似关系在夜间稳定条件下也成立。但是,由于水汽和CO2还受其他因素的影响,相似关系并不适用。更高阶矩的研究表明它们的陡峭度与偏斜度之间存在平方关系。而水汽和CO2之间也存在差异,它们的通量日变化特征明显不同,CO2通量的日变化更能体现人类活动的影响。同时,感热通量、潜热通量和CO2通量存在季节变化,尤其是潜热通量季节差异很大。

Characteristics of Momentum and Scalar Flux in the Urban Boundary Layer

Turbulent statistics(normalized standard deviations,higher order moments,fluxes and spectra and cospectra) in the urban boundary layer are analyzed with data collected from the Beijing 325 m meteorological tower from January to May,2005.Characteristics of spectra and cospectra indicate little influence of stability and more influence of horizontal wind speed on turbulent spectra.Therefore, the similarity relationships of velocity components and temperature is suitable for stable conditions.However,the similarity theory seems not to be fit for water vapor and carbon dioxide for they are affected by other factors.There are square relationships between their kurtosis and skewness.Furthermore,as for daily fluxes,carbon dioxide is different from water vapor,and daily carbon dioxide fluxes reflect the influence of human behavior.Furthermore,sensible heat fluxes,latent heat fluxes and carbon dioxide fluxes change with season.In particular,variance of latent heat fluxes can be very significant.