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931.
932.
933.
Liu Shuhu Liu Heping Liang Fuming Wu Fenglei M. Y. Lecler Xu Mei Hong Zhongxiang Li Jun Liu Huizhi Na Jingyang 《Acta Meteorologica Sinica》1997,11(3):328-337
Described in this paper is an experiment on atmosphere-surface turbulent exchange and boundary layer turbulence properties conducted in July 1994 over the Kerqin Grassland,Jilin,China.The characteristics of the turbulent spectrum,and the relationships of the standard deviation of the turbulent velocity components and sensible heat flux with the atmospheric stability are studied using data from a sonic anemometer and a fast-response platinum resistance thermometer mounted on a 100 m tower.The results show that in the surface layer over a flat,uniform and open grassland,for a broad stability range(-22.12≤ZiL≤17.98),the velocity spectra obey the-2/3 power law in the inertial subrange,and 1 power law at low frequencies.Under near neutral stratification,σu/u*=1.20,σv/u*=1.23 and σw/u*=1.02.For Zi/L≤-0.2,the standard deviations of the turbulent velocity components follow a 1/3 power law.For Zi/L≤-0.1,the standard deviation of the temperature fluctuations follows a-1/3 power law,and as Zi/L≤-0.08,it exhibits nonlinear behavior.Sensible heat flux is well correlated to the stability parameter. 相似文献
934.
用差分光学吸收光谱(DOAS)方法,从曙暮光天顶散射可见光光谱资料反演了北京上空的O3和NO2柱含量,并对反演结果进行了验证和误差分析.斜柱含量的反演采用了线性和非线性最小二乘拟合方法,拟合时考虑了O3、NO2和H2O的吸收、Ring效应和散射的影响;斜柱含量除以空气质量因子转换成垂直柱含量.空气质量因子的计算使用伪球面DISORT辐射传输模式.O3和NO2总量的检验分别用北京的Dobson O3资料和卫星SAGE Ⅱ的NO2廓线资料.反演的O3总量与Dobson O3总量相比偏差小于10%;NO2总量与SAGE Ⅱ的偏差约20%. 相似文献
935.
CHARACTERISTICS OF TURBULENCE SPECTRA IN DIFFERENT WEATHER PROCESSES UNDER UNSTABLE CONDITIONS
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In this paper,the data chosen from measurements by supersonic anemometers in Tongxian County of Beijing in1990 are used to study characteristics of turbulence spectra in precipitation weather.Some turbulence parameters such asturbulence intensity,heat and momentum fluxes,friction velocity,M-O length and stability parameter are calculatedand their dependence on turbulence spectra in different stability conditions are analyzed.Some encouraging results areobtained and compared with others' results. 相似文献
936.
D. Anfossi G. Degrazia E. Ferrero S.E. Gryning M.G. Morselli S. Trini Castelli 《Boundary-Layer Meteorology》2000,95(2):249-270
Eulerian turbulence observations, madein the surface layer under unstable conditions (z/L > 0),by a sonic anemometer were used to estimatethe Lagrangian structure function constant O. Twomethods were considered. The first one makes use of arelationship, widely used in the Lagrangian stochasticdispersion models, relating O to the turbulent kineticenergy dissipation rate , wind velocity variance andLagrangian decorrelation time. The second one employsa novel equation, connecting O to the constant of thesecond-order Eulerian structure function. Beforeestimating O, the measurements were processed in orderto discard non-stationary cases at least to a firstapproximation and cases in which local isotropy couldnot be assumed. The dissipation was estimated eitherfrom the best fit of the energy spectrum in theinertial subrange or from the best fit of the third-orderlongitudinal Eulerian structure function. Thefirst method was preferred and applied to the subsequentpart of the analysis. Both methods predict thepartitioning of O in different spatial components as aconsequence of the directional dependence of theEulerian correlation functions due to the isotropy.The O values computed by both methods are presented anddiscussed. In conclusion, both methods providerealistic estimates of O that compare well withprevious estimations reported in the literature, evenif a preference is to be attributed to the second method. 相似文献
937.
An extention of our previous theory for trace gas absorption into freely-falling cloud and raindrops is presented. This theory describes the convective diffusion of a trace gas through air and into a water drop with internal circulation, the drop falling at its terminal velocity. Using flow fields for the circulating water inside and for the moving air outside the drop, obtained by numerical solutions to the Navier—Stokes equation of motion, we numerically solved the convective diffusion equation to determine the uptake of SO2 by water drops of various sizes, time exposure to the gas phase, and concentration of SO2 in the gas phase. It was found that for drops of radius larger than 1 mm and relatively low gas concentrations (10 ppb (v)), resistance to gas diffusion lies mainly in the gas phase; while for drops of radius less than 500 m and gas concentrations larger than those found in the atmosphere (1% (v)), the resistance to diffusion lies primarily in the liquid phase. With drop sizes and gas concentrations between these limits, the rate of SO2 uptake is controlled by a coupled resistance to diffusion inside and outside the drop. In addition to our general model, a simplified version was formulated which allows considerable savings in computer time for evaluation and improved ease of handling without significant loss of accuracy. A comparison between our simplified model and that of Barrie (1978) shows that the boundary-layer approach of Barrie may be a useful alternate approach to estimating trace gas absorption by water drops, provided appropriate values are chosen for the thickness of the boundary layers involved. 相似文献
938.
The turbulent flow inside dense canopies is characterized by wake production and short-circuiting of the energy cascade. How these processes affect passive scalar concentration variability in general and their spectral properties in particular remains a vexing problem. Progress on this problem is frustrated by the shortage of high resolution spatial concentration measurements, and by the lack of simplified analytical models that connect spectral modulations in the turbulent kinetic energy (TKE) cascade to scalar spectra. Here, we report the first planar two-dimensional scalar concentration spectra (ϕ
cc
) inside tall canopies derived from flow visualization experiments. These experiments were conducted within the deeper layers of a model canopy composed of densely arrayed cylinders welded to the bottom of a large recirculating water channel. We found that in the spectral region experiencing wake production, the ϕ
cc
exhibits directional scaling power laws. In the longitudinal direction (x), or the direction experiencing the largest drag force, the ϕ
cc
(k
x
) was steeper than and followed an approximate at wavenumbers larger than the injection scale of wake energy, where k
x
is the longitudinal wavenumber. In the lateral direction (y), the spectra scaled as up to the injection scale, and then decayed at an approximate
power law. This departure from the classical inertial subrange scaling (i.e., k
−5/3) was reproduced using a newly proposed analytical solution to a simplified scalar spectral budget equation. Near the velocity viscous dissipation range, the scalar spectra appear to approach an approximate k
−3, a tantalizing result consistent with dimensional analysis used in the inertial-diffusive range. Implications to subgrid modelling for large-eddy simulations (LES) inside canopies are briefly discussed. 相似文献
939.
广西秋季层状云微物理特征分析 总被引:1,自引:0,他引:1
利用2012年11—12月在广西进行的11架次飞机云物理探测资料对层状云宏微观物理结构特征进行研究,探讨层状云降水机制。结果表明:广西层状云微物理特征与我国其他地区的存在显著差异。层状云典型的微物理垂直结构为在云下层是由凝结作用生成云滴,随上升气流发展,云滴数浓度、平均直径和液态水含量随高度逐步增加,云滴谱拓宽,谱型向大尺度的方向扩展,至云中上层增大至最大值后随高度减小。冷暖混合云结构的高层云冷云部分的冰相粒子落入暖层后对其微物理结构产生影响,主要是使云滴谱展宽,CIP云滴平均直径垂直分布变幅增大,有利于暖层中碰并过程的启动和发展。层积云微物理水平分布呈现不连续跳跃式变化特征,存在对流泡结构,对流泡内各微物理量高于泡外,云滴谱型向大尺度移动,对流泡结构是层积云形成降水的重要机制。 相似文献
940.