共查询到20条相似文献，搜索用时 906 毫秒
1.
Impact Assessment of Urban Meteorology and the Atmospheric Environment Using Urban Sub-Domain Planning 总被引：3，自引：0，他引：3
For the purpose of (1) investigating the relationship between urban planning and the atmospheric environment, and (2) improving
the atmospheric environment through rational and scientific planning, an urban sub-domain scale model is developed in the
form of a three-dimensional non-hydrostatic model with k – ɛ closure. The distribution and azimuth of buildings, the screening of shortwave radiation by buildings, and the underlying
surface type as characteristics of the urban environment are included, the ground temperature is calculated using the force-restore
method, and the concentration equation is solved simultaneously. The model is evaluated using special field observations and
wind-tunnel experiment data, showing that model results meet the observational and experimental data generally well. Based
on the model, an index system and evaluation method is set up to assess the impact of urban meteorology and the atmospheric
environment using urban sub-domain planning. As an example, two layouts of a specific sub-domain in Beijing are assessed.
The impact assessment system of urban meteorology and the atmospheric environment using urban sub-domain planning, which includes
the urban sub-domain scale numerical model, index system and evaluation method, provides an effective approach to improve
the atmospheric environment through rational and scientific planning. 相似文献
2.
Michael D. Novak 《Boundary-Layer Meteorology》1991,56(1-2):141-161
A model that couples the surface energy balance equation, a surface hydraulic resistance equation, and the force-restore soil temperature model to a mixed-layer model of the planetary boundary layer is described. The mixed layer is separated from the soil by a relatively thin surface layer and is overlain by a stable free atmosphere with prescribed profiles of potential temperature and water vapour density. The model is in reasonably good agreement with daytime micrometeorological measurements made at a wet bare site at Agassiz, British Columbia, and a desert site at Pampa de La Joya, Peru. The sensitivity of the mixed-layer model to conditions in the free atmosphere, to the parameters describing the growth of the mixed layer, and to surface roughness lengths, surface hydraulic resistance, and windspeed is examined. 相似文献
3.
4.
Summary There are numerous approaches to the parameterization of the ground heat flux that use different input data, are valid for
different times of the day, and deliver results of different quality. Six of these approaches are tested in this study: three
approaches calculating the ground heat flux from net radiation, one approach using the turbulent sensible heat flux, one simplified
in situ measurement approach, and the force-restore method. On the basis of a data set recorded during the LITFASS-2003 experiment,
the strengths and weaknesses of the approaches are assessed. The quality of the best approaches (simplified measurement and
force-restore) approximates that of the measured data set. An approach calculating the ground heat flux from net radiation
and the diurnal amplitude of the soil surface temperature also delivers satisfactory daytime results. The remaining approaches
all have such serious drawbacks that they should only be applied with care. Altogether, this study demonstrates that ground
heat flux parameterization has the potential to produce results matching measured ones very well, if all conditions and restrictions
of the respective approaches are taken into account. 相似文献
5.
Simulation of surface urban heat islands under ‘IDEAL’ conditions at night part 1: Theory and tests against field data 总被引：1，自引：0，他引：1
G. T. Johnson T. R. Oke T. J. Lyons D. G. Steyn I. D. Watson J. A. Voogt 《Boundary-Layer Meteorology》1991,56(3):275-294
Observations show that the urban heat island in the atmospheric layer below roof level is most strongly developed during calm, cloudless conditions at night. This paper outlines two versions of a numerical model to describe the cooling of rural and street canyon surfaces under these conditions using surface thermal and radiative properties and the radiative geometry of the canyons. One version uses a full system of differential equations and the other the simpler force-restore approach. The two approaches are shown to be in general agreement and the output of the simpler model is shown to give a faithful representation of cooling of rural and urban surfaces, and therefore heat islands, when compared with field observations. 相似文献
6.
Ground soil heat flux, G 0, is a difficult-to-measure but important component of the surface energy budget. Over the past years, many methods were proposed to estimate G 0; however, the application of these methods was seldom validated and assessed under different weather conditions. In this study, three popular models (force-restore, conduction-convection, and harmonic) and one widely used method (plate calorimetric), which had well performance in publications, were investigated using field data to estimate daily G 0 on clear, cloudy, and rainy days, while the gradient calorimetric method was regarded as the reference for assessing the accuracy. The results showed that harmonic model was well reproducing the G 0 curve for clear days, but it yielded large errors on cloudy and rainy days. The force-restore model worked well only under rainfall condition, but it was poor to estimate G 0 under rain-free conditions. On the contrary, the conduction-convection model was acceptable to determine G 0 under rain-free conditions, but it generated large errors on rainfall days. More importantly, the plate calorimetric method was the best to estimate G 0 under different weather conditions compared with the three models, but the performance of this method is affected by the placement depth of the heat flux plate. As a result, the heat flux plate was recommended to be buried as close as possible to the surface under clear condition. But under cloudy and rainy conditions, the plate placed at depth of around 0.075 m yielded G 0 well. Overall, the findings of this paper provide guidelines to acquire more accurate estimation of G 0 under different weather conditions, which could improve the surface energy balance in field. 相似文献
7.
John D. Wilson 《Boundary-Layer Meteorology》2007,125(1):39-47
Well-mixed, first-order Lagrangian stochastic (LS) particle trajectory models are derived from several idealized (“toy”) turbulent
velocity distributions, and their performance is compared against the observations of Project Prairie Grass, i.e., the case
of a continuous point source of tracer near the ground, in the horizontally homogeneous and neutrally stratified surface layer.
Although in a context of limited information a Gaussian distribution is the preferred choice, and although the Gaussian corresponds
to the simplest of this set of LS models (namely, the Langevin equation), models stemming from other velocity distributions
give similar, albeit distinguishable, predictions. 相似文献
8.
Brian P. Reen David R. Stauffer Kenneth J. Davis Ankur R. Desai 《Boundary-Layer Meteorology》2006,120(2):275-314
The importance of soil moisture inputs and improved model physics in the prediction of the daytime boundary-layer structure during the Southern Great Plains Hydrology Experiment 1997 (SGP97) is investigated using the non-hydrostatic fifth-generation Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) Mesoscale Model MM5. This is Part II of a two-part study examining the relationship of surface heterogeneity to observed boundary-layer structure. Part I focuses on observations and utilizes a simple model while Part II uses observations and MM5 modelling. Soil moisture inputs tested include a lookup table based on soil type and season, output from an offline land-surface model (LSM) forced by atmospheric observations, and high-resolution ( 800 m) airborne microwave remotely sensed data. Model physics improvements are investigated by comparing an LSM directly coupled with the MM5 to a simpler force-restore method at the surface. The scale of land surface heterogeneities is compared to the scale of their effects on boundary-layer structure.The use of more detailed soil moisture fields allowed the MM5 to better represent the large-scale (hundreds of km) and small-scale (tens of km) horizontal gradients in surface-layer weather and, to a lesser degree, the atmospheric boundary-layer (ABL) height, which was evaluated against observations measured by differential absorption lidar (DIAL). The benefits of coupling an LSM to the MM5 were not readily evident in this summertime case, with the model having particular difficulty simulating the timing of maximum surface fluxes while underestimating the depth of the mixed layer. 相似文献
9.
We show that traditional Reynolds (block) averaging produces turbulence statistics whose time evolution is incompatible with the Navier–Stokes equation. Specifically, the zero integral scale that block averaging always produces leads to a trivial (zero-equals-zero) solution of the Navier–Stokes equation for autocovariances. We suggest alternative methods for analyzing turbulence time series that do not always generate a zero integral scale and, as a result, yield autocovariances whose time evolutions are compatible with the Navier–Stokes equation. 相似文献
10.
In terms of Kuo-Qianp-sigma incorporated coordinate five-level primitive equation spheric band (70°N–30°S) model with the Ural high’s effect introduced
into it as initial and boundary conditions, study is made of the high’s influence on Asian summer monsoon circulation and
dryness/wetness of eastern China based on case contrast and control experiments. Rusults show that as an excitation source,
the blocking high produces a SE–NW stationary wavetrain with its upper-air atnicyclonic divergent circulation (just over a
lower-level trough zone) precisely over the middle to lower reaches of the Changjiang River, enhancing East Asian westerly
jet, a situation that contributes to perturbation growth, causing an additional secondary meridional circulation at the jet
entrance, which intensifies the updraft in the monsoon area. As such, the high’s presence and its excited steady wavetrain
represent the large-scale key factors and acting mechanisms for the rainstorm over the Changjiang-Huaihe River catchment in
the eastern part of the land.
This study is supported by the National Basic Research of Major Key Projects of China. 相似文献
11.
上海城市精细化地表温度分布模拟 总被引：2，自引：0，他引：2
本文引入了一种模拟城市复杂下垫面地表温度的方法,该方法基于地表辐射参数化方案（NARP）计算城市净辐射通量,然后利用客观滞后模型OHM计算地表储热通量,再利用强迫恢复法计算表面温度。通过上海地区高分辨率卫星资料获取不同地表类型覆盖比例,以每个格点中各地表覆盖类型所占面积比例为权重计算格点的平均地表温度,并对2013年8月12日上海地区地表温度进行模拟。结果表明：上海城市下垫面与其他类型下垫面相比,地表温度白天升高较快,而夜间下降较慢。模拟结果与MODIS陆面温度及地面观测资料进行比较,模拟的上海地表温度分布结构更精细,与气象站观测值较接近。 相似文献
12.
13.
V. R. Fuks 《Russian Meteorology and Hydrology》2009,34(8):528-533
An approach is proposed for analysis and interpretation of satellite measurements of oceanographic fields (sea surface temperature,
turbidity, chlorophyll concentration, and altimetry data) herein referred to as “dynamic-stochastic analysis.” This approach
consists in (1) representing spatiotemporal variability of measured characteristics as a partial differential equation which
satisfies the basic conservation lows and which is solved for the rate of change of this characteristic; (2) interpretation
of this differential equation as a multiple regression equation, where the rate of characteristic change is the predictand
and all other spatial and spatiotemporal derivatives are predictors, and (3) estimation of the regression coefficients of
this equation and their physical interpretation. This analysis was applied to satellite altimetry measurements and measurements
of primary production in the Sea of Japan and White Sea. The results are considered in this paper. 相似文献
14.
Solutions to the sheared Fickian advection–diffusion equation in a half-space with arbitrary surface source are given using
a ‘transfer function’ method. The method uses Fourier transforms in two horizontal coordinates and time, along with complex
Airy functions in the vertical coordinate. Surface deposition and tracer decay are included in the formulation. ‘Puff’ and
steady ‘plume’ solutions are compared with Saffman’s moment formulae. The inclusion of a decay rate factor (α) allows the
average tracer age to be computed from steady state solutions for concentration C(x, y, z) according to Age = − dln C/dα. A comparison between the puff centroid formula of Saffman and plume Age computations confirms that shear causes tracer puffs
to accelerate horizontally as they diffuse upward into a different wind regime. In forward shear, tracer ages are younger
than in unsheared flow but the range of ages is greater due to the existence of a high fast pathway and a low slow pathway.
In reverse shear, concentrations, ages and the range of ages all rise markedly near the source. Large tracer age suggests
that some tracer has taken a very distant path involving a low-level outbound trip and a high-level return. The effect of
surface deposition is to reduce the influence of the distant path. In the case of reverse shear, deposition makes the tracer
younger. In a turning wind, the time needed to reach a given radius increases due to the curved path of the plume. 相似文献
15.
The turbulence closure in atmospheric boundary-layer modelling utilizing Reynolds Averaged Navier–Stokes (RANS) equations
at mesoscale as well as at local scale is lacking today a common approach. The standard kɛ model, although it has been successful for local scale problems especially in neutral conditions, is deficient for mesoscale
flows without modifications. The k–ɛ model is re-examined and a new general approach in developing two-equation turbulence models is proposed with the aim of
improving their reliability and consequently their range of applicability. This exercise has led to the replacement of the
ɛ-transport equation by the transport equation for the turbulence inverse length scale (wavenumber). The present version of
the model is restricted to neutrally stratified flows but applicable to both local scale and mesoscale flows. The model capabilities
are demonstrated by application to a series of one-dimensional planetary boundary-layer problems and a two-dimensional flow
over a square obstacle. For those applications, the present model gave considerably better results than the standard k–ɛ model. 相似文献
16.
Stable and Unstable Eigensolutions of Laplace’s Tidal Equations for Zonal Wavenumber Zero 总被引：1，自引：0，他引：1
Rolf Müller 《大气科学进展》1993,10(1):21-40
Laplace's tidal equations are of great importance in various fields of geophysics. Here, the special case of zonal symmetry (zonal wavenumber m = 0) is investigated, where degenerate sets of eigensolutions appear. New results are presented for the inclusion of dissipative processes and the case of unstable conditions. In both instances the (nonzero) eigenfrequencies are complex. In the latter case, additional stable (i.e. real) eigenfrequencies appear in the numerical results for the absolute value of the Lambparameter ε being larger than a critical value εc. Further, it is shown that any degeneracies are removed through the inclusion of dissipation. Moreover, asymptotic relations are derived employing the relation of Laplace's tidal equations for m = 0 to the spheroidal differential equation. The implications of these findings to numerical techniques are demonstrated and results of computations are presented. 相似文献
17.
近年来,一类由Itô随机微分方程驱动的奇异随机系统因其在实际领域中的广泛应用而备受关注.然而,系统方程同时包含奇异矩阵和扩散矩阵,大大增加了分析问题的复杂性.本文首先概述了奇异Itô随机系统几个重要基础问题的研究进展,主要包括:系统方程解的存在条件、广义Itô公式、容许性定义及稳定性问题.同时针对不同文献对上述问题的研究结果提出了自己的观点.最后对以上基础问题研究待解决的问题进行了展望. 相似文献
18.
A self-consistent two-equation closure treating buoyancy and plant drag effects has been developed, through consideration of the behaviour of the supplementary equation for the length-scale-determining variable in homogeneous turbulent flow. Being consistent with the canonical flow regimes of grid turbulence and wall-bounded flow, the closure is also valid for homogeneous shear flows commonly observed inside tall vegetative canopies and in non-neutral atmospheric conditions. Here we examine the most often used two-equation models, namely and E − ω (where is the dissipation rate of turbulent kinetic energy, E, and is the specific dissipation), comparing the suggested buoyancy-modified closure against Monin–Obukhov similarity theory. Assessment of the closure implementing both buoyancy and plant drag together has been done, comparing the results of the two models against each other. It has been found that the E − ω model gives a better reproduction of complex atmospheric boundary-layer flows, including less sensitivity to numerical artefacts, than does the model. Re-derivation of the equation from the ω equation, however, leads to the model implementation that produces results identical to the E − ω model. Overall, numerical results show that the closure performs well, opening new possibilities for application of such models to tasks related to the atmospheric boundary layer—where it is important to adequately account for the influences of both vegetation and atmospheric stability. 相似文献
19.
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
20.
Andrey Sogachev 《Boundary-Layer Meteorology》2009,130(3):423-435
The note presents a rational approach to modelling the source/sink due to vegetation or buoyancy effects that appear in the
turbulent kinetic energy, E, equation and a supplementary equation for a length-scale determining variable, φ, when two-equation closure is applied to canopy and atmospheric boundary-layer flows. The approach implements only standard
model coefficients C
φ1 and C
φ2 in the production and destruction terms of the φ equation, respectively. Numerical tests illustrate the practical applicability of the method, where, for example, simulations
with the E–ω model (where is the specific dissipation and is the dissipation rate of E) properly reproduce both the surface-layer wind profile estimated from the Monin-Obukhov similarity theory and the mixing-height
evolution observed above forested terrain in Southern Finland. 相似文献