【作者】 姚文清；

【导师】 徐祥德； 周明煜；

【作者基本信息】 中国气象科学研究院 ， 气象学， 2005， 博士

【摘要】 人类的生存环境与大气边界层息息相关。进入20世纪以来,由于工业、交通的发展,尤其是城市化进程的加剧,城市边界层特征变得日趋复杂,影响因素诸多,使其物理化学过程难以认识。为了保护人类生存环境,建立城市环境良性循环的结构,进而调控城市大气污染状况,对城市边界层大气动力和大气化学特征及其相互作用机理的研究已成为直接影响社会、经济发展的重大课题。北京作为我国的首都,其城市化环境问题尤为突出和重要。本文利用“BECAPEX”大气环境科学试验北京气象塔15层梯度观测资料、三层超声风温仪观测资料以及系留气艇垂直探测资料,通过对北京城市边界层大气过程垂直动力特征的综合研究,揭示北京城市边界层不同层次湍流特征及北京地区与其它不同城市和不同类型下垫面地区湍流特征的差异,研究了不同城市灾害性天气过程沙尘天气和城市大雾天气过程的城市边界层垂直动力结构尤其是湍流垂直结构的特征及其与污染物浓度变化的关系,同时通过修正数值模式中城市下垫面动力学参数改善了模式对边界层结构的模拟效果,并进一步研究了城市下垫面特征的变化对边界层动力、热力及湍流的影响特征。初步揭示了北京城市边界层湍流动力结构模型。 主要结论概括如下: (1) 对北京城市边界层垂直方向不同层次湍流特征的综合研究结果表明:在不稳定层结条件下,北京城市边界层47m和120m高度上无因次湍流速度方差(σ_u/u*、,σ_v/u*、σ_w/u*)与空气动力学稳定度参数(z’/L)之间关系符合1/3次律,无因次温度方差(σ_T/T*)符合-1/3次律,并给出相应的拟合公式。而280m高度上资料离散度较大,缺乏拟合基础;47m和120m高度的湍流通量特征比较相近,280m明显低于其它两层,在白天,近地层包含了47m和120m,而280m则已在近地层之上;在稳定层结条件下,47m高度大气边界层可按稳定度参数.z’/L分成二分区,z’/L<0.1为弱稳定区,此时相似规律可适用,z’/L>0.1为强稳定区,在此区内无因次速度方差随稳定度增大有增大趋势,而无因次温度方差则保持不变,相似规律不适用。120m和280m高度则无上述规律。 (2) 北京城市边界层各高度无因次速度方差的大小都表现为,σ_u/u*最大,σ_v/u*次之,σ_w/u*最小。在垂直方向上,σ_u/u*随高度增加而增大,σ_v/u*、σ_w/u*随高度变化都表现为在47m和120m的值比较接近,280m处的值高于其它两层的值。城更多还原

【Abstract】 The environment of human subsistence has a close relation with atmospheric boundary layer processes. Since 20’s century, for the development of industry and traffic, especially for the quicken-up of urban trend, the characteristics of urban boundary layer (UBL) become more and more complex. Due to its too many impact factors, it is very difficult to recognize the mechanism of physical and chemical processes of UBL. So in order to protect the environment of human subsistence and set up a benign circulation structure of urban environment to control urban air pollution, study on UBL air dynamical structure characteristics and their coupling mechanism with chemical process has became an exigent project that will effect the development of society and economy. As our capital, Beijing’s urban environment problem is more important and noticeable. By utilizing vertical observational data of "BECAPEX" (Beijing City Air Pollution Observation field experiment), including 15 levels gradient data, 3 levels ultra-sonic data, tethersonde profiler data and so on, the integrated studies on Beijing UBL processes vertical structure features are carried out. Characteristics of Beijing UBL turbulent vertical structure and its difference with other cities and underlying surface are disclosed. The UBL vertical dynamical structure characteristics especially its turbulent vertical structure features and their relations with pollutant concentration during different urban catastrophic events as sand/dust weather and city fog process are studied. Meanwhile, by amending aerodynamic parameters in numerical model, the simulation capacity of it is improved. Furthermore, the effects of change in urban underlying surface on UBL dynamical, thermal and turbulent structure are investigated. So the basic turbulence dynamical pattern of Beijing UBL is disclosed through all above studies. The main conclusions are as follows:(1) Integrated studies on turbulence vertical structure of Beijing UBL suggest: Under unstable condition, the normalized turbulent wind standard deviation (σ_u/μ*σ_v/μ* σ_w/μ* ) and turbulent temperature standard deviation (σ_T/T*)at height of 47 and 120m follow the Monin-Obukhov similarity theory and its normalized function are given out as well. But data at height of 280m is scattered and does not follow the M-0 theory. At day time the near surface layer includes heights of 47 and 120m while 280m has beyond it. Under stable condition, according to the value of dimensionless stability parameter (z’ /L), the stable near surface layer of 47m could be divided into two regions. When z’/L<0.1 it is weak stable region where the M-0 similarity theory can be applicable. The other is strong stable region when z ’/L>0.1. In this region the normalized turbulent wind standard deviation increase with stability but the normalized turbulent temperature standard deviation remain constant and thesimilarity theory can not be applied. And this phenomenon can not be found at height of 47 and 120m at stable condition.(2) At all height of Beijing UBL, comparison of normalized turbulent wind standard deviation in different direction show that the value of σ_u/μ* is largest, then it is σ_v/μ*, σ_w/μ* is the smallest. As to vertical direction, σ_u/μ* increase as height increase. To σ_v/μ* and σ_w/μ*, their values at 47 and 120m are very close while the value at 280m is larger than that two layers. The urban underlying surface leads to the decreased normalized turbulent wind standard deviation but increased turbulent intensity in near surface of Beijing. And the impact is more remarkable in horizontal direction then in vertical direction.(3) The drag coefficient (Co) of Beijing underlying surface increases as z’/L increases but decreases as height increases. Under near-neutral condition, C_D at the height of 47m is between 0.1-1, for 120m it is 0.01-0.1, and for 280m it is 0.001-0.1 and centered near 0.01. Compared to that of the different underlying surface, C_D in near surface of Beijing has increased considerably.(4) The particle air更多还原