大气和海洋科学快报（英文版）2021，Vol.14Issue(1)：52-56,5.
基于北京325米气象塔观测的正,负湍流热扩散系数
Positive and negative turbulent heat diffusivity observed on a 325-m meteorological tower in Beijing
摘要
Abstract
Turbulent diffusion efficiently transports momentum,heat,and matter and affects their transfers between the atmosphere and the surface.As a key parameter in describing turbulent diffusion,the turbulent heat diffusivity KH has rarely been studied in the context of frequent urban pollution in recent years.In this study,KH under urban pollution conditions was directly calculated based on K-theory.The authors found an obvious diurnal variation in KH,with variations also in the vertical distributions between each case and over time.Interestingly,the height corresponding to the high occurrence frequency of negative KH rises gradually after sunrise,peaks at noon,falls near sunset,and concentrates around 140 m during most of the night.The KH magnitude and fluctuation are smaller in the pollutant accumulation stage (CS) at all levels than in the pollutant transport stage and pollutant removal stage.Turbulent diffusion may greatly affect PM2.5 concentrations at the CS because of the negative correlation between PM2.5 concentrations and the absolute value of KH at the CS accompanied by weak wind speeds.The applicability of K-theory is not very good during either day or at night.These problems are inherent in K-theory when characterizing complex systems,such as turbulent diffusion,and require new frameworks or parameterization schemes.These findings may provide valuable insight for establishing a new turbulence diffusion parameterization scheme for KH and promote the study of turbulent diffusion,air quality forecasting,and weather and climate modeling.关键词
湍流热扩散系数/逆梯度运输/大气边界層/城市污染Key words
Turbulent heat diffusivity/Counter gradient transportation/Atmospheric boundary layer/Urban pollution引用本文复制引用
Zhe Zhang,Yu Shi,Haijion Sun,Lei Liu,Fei Hu..基于北京325米气象塔观测的正,负湍流热扩散系数[J].大气和海洋科学快报（英文版）,2021,14(1):52-56,5.基金项目
This work was jointly supported by the National Natural Science Foundation of China[grant numbers 41975018 and 41675012]and the National Key Research and Development Program of China[grant number 2017YFC0209605]. （）
