共查询到20条相似文献，搜索用时 31 毫秒
1.
利用考虑地形和水平扩散作用的正压涡度方程,在线性情况下,给出了描写对称运动和反对称运动(都是对赤道来说的)的方程和它们各自的解析解。分析这些解可以看出,不论对于对称运动或反对称运动,解都由三部份组成:一是与初始流场有关的Rossby波;一是以Rossby波波速传播的,与地形和水平扩散有关的行进波;另一是与地形和水平扩散有关的定常波。但是,如初始时刻运动是对称的,则地面拔海高度和水平扩散系数的反对称分布可以引起反对称运动,从而,引起非对称的运动。在定常情况下,则对称的流场,和地面拔海高度、水平扩散系数的对称分布有关,反对称的流场,和地面拔海高度、水平扩散系数的反对称分布有关。最后,还用数值试验,证明反对称地形可以引起反对称运动;还讨论了南北半球的相互影响的问题。 相似文献
2.
Atmospheric air pollution turbulent fluxes can be assumed to be proportional to the mean concentration gradient. This assumption, along with the equation of continuity, leads to the advection–diffusion equation. Moreover, large eddies are able to mix scalar quantities in a manner that is counter to the local gradient. In this work we present a semi-analytical solution for the three-dimensional steady-state advection–diffusion equation, considering non-local turbulence closure using the Generalized Integral Advection Diffusion Multilayer Technique (GIADMT). We report some examples of applications of the new solution for two different datasets and for a water tank experiment. 相似文献
3.
F. A. Gifford 《Boundary-Layer Meteorology》1984,30(1-4):159-175
The physical basis for the random force theory of atmospheric diffusion is briefly reviewed. The random force equation has usually been introduced as an atmospheric analogy to Brownian motion. Here it is derived by assuming a type of Rayleigh friction in the Lagrangian equations of atmospheric motion. Consequences, including the Lagrangian correlation and spectrum, the particle-particle intercorrelation, and cluster and plume dispersion and meandering, are derived and compared with atmospheric observations. The characteristic time-scale of atmospheric diffusion is shown to be governed by the Coriolis effect, a result in good agreement with meso- and large-scale observations. 相似文献
4.
5.
6.
EFFECTS OF OROGRAPHY AND HORIZONTAL DIFFUSION ON THE GENERATION OF THE ASYMMETRIC MOTION IN THE BAROTROPIC FILTERED MODEL ATMOSPHERE 
下载免费PDF全文
下载免费PDF全文 By utilizing the barotropic vorticity equation including effects of orography and horizontal diffusion,the linearized equations describing symmetric and antisymmetric motions and their analytic solutions are pre-sented.It can be found from the solutions that no matter what kind of motion may be,each solution consistsof three waves,namely,Rossby wave related to initial values,marching wave propagating at Rossby wavevelocity and stationary wave.The latter two are closely related to orography and horizontal diffusion.However,if the motion is symmetric at the initial instant,then the antisymmetric components of orographyand of horizontal diffusion are likely to lead to the generation of antisymmetric motion.In the steady state,the symmetric flow is connected with symmetric orography and horizontal diffusion and the antisymmetricflow with antisymmetric orography and horizontal diffusion.Further,in order to verify the above analysis,three numerical experiments have been made.The results show that antisymmetric orography can produceantisymmetric motion.Finally,the atmospheric interactions between Northern and Southern Hemispheresare discussed. 相似文献
7.
A model was developed for pollutant dispersion from a point source simulating the Hadera (Israel) power plant stack. The model is based on the NCAR mesoscale meteorological MM4 model that provides the wind fields and coefficients of turbulent diffusion. The model was implemented using an implicit numerical scheme with changing directions. A comparison between the model calculations and an analytical solution for the advection-diffusion equation shows good agreement. Relatively low numerical diffusion of the adopted advection scheme was noted. Results for the hilly region of central Israel are presented for a summer case. 相似文献
8.
多尺度大气湍流的扩散及扩散率 总被引：5，自引：3，他引：5
本文首先将大气湍流多尺度化,而将不同尺度的脉动量的Monte Carlo关系转换为Lange-vin方程,在平稳及均匀条件下可得一高阶常系数Lagrange自相关函数的常微分方程。其通解恰为一组衰减实指数函数的线性组合,系数为各尺度湍能对总湍能的比。以此可通过Taylor积分对野外实测扩散参数作出尺度分解。并可方便地将扩散参数表达为湍流参数的函数使其物理意义明确。 相似文献
9.
J. Egger 《Climate Dynamics》2001,18(1-2):169-177
A data set comprising the equatorial components of global atmospheric momentum and the related mountain and friction torques
is used to demonstrate the usefulness of a novel analysis technique in climate research. The technique consists in deriving
a Master equation in the phase plane of a pair of climate variables on the basis of time series of this pair. The Master equation
predicts changes of the pair's probability distribution in this phase plane. A mean velocity and a diffusion coefficient can
be derived from the coefficients of this equation. An analysis of the dynamics of the parameter pair is based on the Master
equation. The circulation of the angular momenta in the phase plane is anticyclonic with an attraction towards the origin.
The diffusion is strongest close to the center of the probability density distribution of the equatorial momenta. The anticyclonic
motion reflects the westward propagation of those Rossby waves which contribute to the mass term. It is found that the mountain
and orographic torques induce only a small fraction of the observed changes of the angular momenta. It is essentially the
impact of both the Earth's deviation from sphericity and its rotation, which induces the variability of the angular momenta.
The mass and wind terms are barely related to each other in contrast to the predictions of normal mode theory. Surprisingly,
however, the mountain torque and the wind terms are closely linked.
Received: 13 April 2000 / Accepted: 22 February 2001 相似文献
10.
本文就区域尺度大气污染物浓度预报，提出一种以天气气候学分型为基础，结合大气污染物输放散区域污染物浓度区域分布逐日预报模式；并用该模式作预报试验，结果表明：模式的预报结果能达到一定的正确率，具有实用价值。 相似文献
11.
12.
A 5-layer primitive equation Northern Hemisphere operational model in a modified σ-coordinate system is developed in BMC,
NMB. Finite difference schemes are constructed to conserve the total energy without imposing any constraints on the difference
scheme of hydrostatic equation and pressure gradient term.
The physical factors of orography, friction, horizontal diffusion and various non-adiabatic heatings are included.
The model has been under development since the beginning of 1980, and became operational in September 1981. Preliminary results
for selected series of 40 prognosis are summarized and the verifications are encouraging. 相似文献
13.
Mathematical model for hermitized atmospheric dispersion in low winds with eddy diffusivities as linear functions of down wind distance 总被引：1，自引：0，他引：1
Summary In the present paper, an attempt is made for generalized the atmospheric diffusion operator. This can be accomplished by employing
the realizability procedure, to identify a surface operator, that ensures self-adjointness’ of the atmospheric diffusion operator.
The dispersion modeling in low wind speeds assumes importance because of the high frequency of occurrence and episodic nature
of these poor diffusion conditions. A steady-state mathematical model for hermitized model has been calculated for the dispersion
of air pollutants in low winds by taking into account the diffusion in the three coordinate directions and advection along
the mean wind. The eddy diffusivities have been parameterized in terms of downwind distance for near source dispersion (Arya,
1995). The constants involved in this parameterization are the squares of intensities of turbulence. An analytical solution
for resulting advection-diffusion equation with the physically relevant boundary conditions has been obtained. The solution
has been used to simulate the field tracer data collected at IIT Delhi in low wind convective conditions. 相似文献
14.
Branko Grisogono 《Boundary-Layer Meteorology》1990,52(3):221-225
A simple equation of diffusion is derived from the longwave radiative flux transfer equation for the atmospheric stable nocturnal boundary layer. This simplification is valid with clear-sky conditions, light wind speeds and near the top of the inversion layer which has already been established.The known physical behavior of such a layer in the given conditions (the weak and slow destabilization, and spreading of the top of the inversion layer) is explained by this simple equation of mathematical physics instead of a complicated expression written in terms of the net longwave radiative flux divergence. 相似文献
15.
本文根据大气中NO_2形成HNO_3的主要化学反应求解带有化学反应的扩散方程而得到HNO_3生成量的空间分布。HNO_3气体形成后边扩散边被降水清洗带至地面。我们又求解了HNO_3气体的扩散方程,考虑降水清洗从而得到HNO_3被降水带至地面的湿沉降量,得到水平面上HNO_3在24h内的分布,可用来大致估计HNO_3污染程度及范围。 相似文献
16.
17.
B. V. Arkhipov V. N. Koterov V. V. Solbakov D. A. Shapochkin Yu. S. Yurezanskaya 《Russian Meteorology and Hydrology》2007,32(6):377-387
We consider features of the application of a discrete particle statistical method to solve the transport and diffusion equation in the case of the time-dependent (contaminant transport by turbulent flow) or nonlinear (thin slick spreading on the water surface) diffusion rate. For the problem of contaminant dispersion by turbulent flow, an algorithm is developed for discrete particle technique application in the case of the diffusion rate change governed by “4/3 law,” and a good agreement of numerical and analytical results is demonstrated. For the problem of oil slick spreading, as described by the quasi-linear transport-diffusion equation, an algorithm of the particle random walk is developed, in which the walk step dispersion depends on the unknown function. The solution using a discrete particle technique for both volley and continuous discharge is in good agreement with analytical and/or numerical solutions using the grid method (the latter is practically equivalent to the analytical solution due to small time and space steps for a one-dimensional axisymmetric case). 相似文献
18.
使用近年来PBL内实测平均风,湍流统计量和拉氏时间尺度随高度变化的结果,对用最简单的二阶闭合假设导出的三维定常物质连续方程作数值解,分析讨论了风速、风向和湍流统计特征量的垂直切变以及粗糙长度z_0对PBL内浓度分布的影响。本文的结果对PBL内湍流扩散本质的认识及污染模式的建立均有益处。 相似文献
19.
在寻求层状云中催化剂扩散议程的解时，一般都假定风速为常值，但实际上风速是随高度变化的。该文在云中催化剂的数值模式中考虑了风速随高度的变化，用差分格式求其解，并进行了个例计算和比较分析。 相似文献
20.
John G. Papageorgiou 《Boundary-Layer Meteorology》1988,45(1-2):9-29
A 3-D sea breeze model has been developed to study the sea breeze and the pollutant dispersion over a coastal area. Topography is also included. Similarity theory is adopted while a turbulent kinetic energy equation is used to study turbulence and to parameterize eddy diffusion. The integration is repeated in diurnal cycles and the results — meteorological and pollutant — are compared with data from the Athens area. 相似文献