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1.
Walmsley's (1992) proposal for a new PBL Resistance Law required blending between surface- and matched-layer logarithmic velocity profiles. Here it is suggested that blending should be restricted to the matched layer, in contrast to Walmsley's original formulation in which blending was done in the surface layer. This modification does not have any noticeable effect on the wind speed profile and only minimal impact on the wind shear, but it yields more realistic profiles of wind direction. In particular, all the adjustment of wind direction takes place above the surface layer. 相似文献
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An efficient, pianetary boundary layer (PBL) model is developed and validated with empirical data for applications in general circulation models (GCMs). The purpose of this PBL model is to establish the turbulent surface fluxes as a function of the principal external PBL parameters in a numerically efficient way. It consists of a surface layer and a mixed layer matched together with the conditions of constant momentum and heat flux at the interface. An algebraic solution to the mean momentum equations describes the mixed-layer velocity profile and thus determines the surface wind vector. The velocity profile is globally valid by incorporating the effect of variable Coriolis force without becoming singular at the equator. Turbulent diffusion depends on atmospheric stability and is modeled in the surface layer by a drag law and with first-order closure in the mixed layer. Radiative cooling in the stably stratified PBL is considered in a simple manner. The coupled system is solved by an iterative method. In order to preserve the computational efficiency of the large-scale model, the PBL model is implemented into the GISS GCM by means of look-up tables with the bulk PBL Richardson number, PBL depth, neutral drag coefficient, and latitude as independent variables.A validation of the PBL model with observed data in the form of Rossby number similarity theory shows that the internal feedback mechanisms are represented correctly. The model, however, underpredicted the sensible heat-flux. A subsequent correction in the turbulence parameterization yields better agreement with the empirical data. The behavior of the principal internal PBL quantities is presented for a range of thermal stabilities and latitudes. 相似文献
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S. S. Zilitinkevich 《Boundary-Layer Meteorology》1989,49(1-2):1-5
A logarithmic + polynomial approximation is proposed for the vertical temperature profile in a neutrally or stably stratified planetary boundary layer (PBL) in conditions of quasi-stationarity. Using this approximation with the asymptotic logarithmic + linear law of the Monin-Obukhov similarity theory for the near-surface layer and with the Zilitinkevich formula for the PBL thickness allows one to derive an analytical expression for the function C in the heat transfer law, which permits simple parameterization of the thermal interaction between the atmosphere and the underlying medium in terms of external parameters, such as the geostrophic wind velocity and the temperature difference across the PBL. 相似文献
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S. S. Zilitinkevich 《Boundary-Layer Meteorology》1989,46(4):367-387
The logarithmic + polynomial approximation is suggested for vertical profiles of velocity components in a planetary boundary layer (PBL) at neutral and stable stratification. The resistance law functions A and B are determined on the basis of this approximation, using integral relations derived from the momentum equations, the Monin-Obukhov asymptotic formula for the wind profile in a stably stratified near-surface layer and the known expressions for the PBL depth. This result gives a realistic and convenient method for calculating the surface friction velocity and direction and the total dissipation rate of mean flow kinetic energy in terms of geostrophic velocity, buoyancy flux at the surface, the roughness parameter and the Coriolis parameter. In the course of these derivations a review is given of current views on the main problems of the neutral and stable PBL. 相似文献
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塔克拉玛干沙漠腹地大气边界层参数化方案的模拟评估 总被引：1，自引：0，他引：1
沙尘起沙、沉降、传输均受到沙漠地区大气边界层条件的制约。沙漠地区观测资料匮乏,限制大气边界层模拟效果的检验和评估。利用WRFV3.7.1中尺度数值模式中5种边界层参数化方案(ACM2、BL、MYJ、MYNN2.5、YSU),模拟2014年4月塔克拉玛干沙漠大气边界层特征,并与塔中80 m塔及风廓线雷达晴朗天气下的观测资料对比分析。结果表明:5种方案均能模拟出近地面气温及地表温度,边界层高度,感热、潜热、地表热通量的变化趋势,但未能模拟出边界层风速的日变化趋势,温风湿廓线能较好的反映晴日沙漠地区边界层结构的变化特征,但未模拟出风速随高度变化趋势。沙漠地区下垫面干燥,热容量低,晴天极易形成对流不稳定边界层,非局地湍流参数化方案,ACM2方案是沙漠地区大气边界层模拟较为合理的选择。 相似文献
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A quantitative method for estimating Pasquill stability class from windspeed and sensible heat flux density 总被引：1，自引：0，他引：1
A simple exponential expression, based upon a form of the Kazanski-Monin stability parameter, modified to account explicitly for effects of surface roughness, and semi-empirically derived from both qualitative and quantitative observations, is presented that relates windspeed and sensible heat flux density to Pasquill stability class. The method, though simple in mathematical form, gives results consistent with physical intuition and reproduces, quantitatively, the essential features of previously published nomograms with an added capability for treating all stability classes and any surface roughness from 0.10 to 100 cm. For the stable classes, a new expression for the wind profile stability factor, predicted by similarity theory, is introduced that produces results more consistent than the more common linear form. 相似文献
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A numerical model of a non-stationary atmospheric planetary boundary layer (PEL) over a horizontally homogeneous flat surface is derived on the basis of similarity theory. The two most typical turbulence regimes are reproduced: one corresponding to a convectively growing PBL and another corresponding to a stably stratified quasi-equilibrium PBL. The PBL is treated as a unit. Hence, its evolution is characterized by temporal changes of intrinsic parameters, such as the PBL depth, the vertically averaged values of potential temperature, specific humidity and components of wind velocity, the near-surface values of heat, water vapor and momentum fluxes. The internal structure of the PBL is considered self-similar. This allows one to represent the interaction between the air flow and the underlying surface by means of universal heat/mass transfer and resistance laws. Numerical experiments on the diurnal variations of meteorological fields in the lower 2 km layer confirm the ability of the model to reproduce the main features of the phenomena, known from observations.On leave from: Insitute of Limnology, Academy of Sciences of the Russia, SU-196199, St. Petersburg, Russia. 相似文献
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W. C. Ulrich 《Meteorology and Atmospheric Physics》1993,52(1-2):69-89
Summary A simple one dimensional wind model, designed for diffusion calculations in flat environments with obstructions, is proposed. It covers the surface layer and up to a maximum height of 500 m with three levels. The lowest level is the internal boundary layer, in which the influence of the immediate environment is manifest. The second is the surface layer in which the wind profile is characterized by the fetch conditions further upstream. The third is the spiral layer, where the wind turns with height. The actual depth of the surface layer is estimated by the model. In both the surface layer and the internal boundary layer, Monin-Obukhov theory is applied. The spiral layer is represented by a classical Ekman-Taylor solution matched at the top of the surface layer. This conceptual model is then tested with data from a meteorological mast at Garching (near Munich, Germany).With 11 Figures 相似文献
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Shih-Ang Hsu 《Boundary-Layer Meteorology》1972,2(3):284-289
Under persistent onshore trade-wind conditions, the wind profile was measured in the surface layer on a mud flat of the tidal stream of Estero de Data, Gulf of Guayaquil, Ecuador. It was found that the logarithmic wind relation fitted the observations very well and that the inferred shear velocity was a linear function of wind speed in the range of wind velocity studied. 相似文献
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以北京市观象台2010年8月、2011年8月每日3次 (08:00, 14:00, 20:00,北京时,下同) L波段探空秒间隔数据为实况,对BJ-RUC系统 (rapid updated cycle system for the Beijing area) 分析和预报边界层性能进行了初步评估。结果表明:BJ-RUC系统对北京地区夏季白天边界层的细致特征具有较好的预报能力,但也存在明显的系统性误差。08:00边界层偏冷; 14:00和20:00 1 km以下的边界层则显著偏暖, 边界层内明显偏湿。整体上模式对边界层内温度、湿度的预报误差均高于自由大气。该系统对北京地区边界层内早晨 (08:00) 从夜间山风向白天谷风环流过渡、午后 (14:00) 到日落后 (20:00)1500 m以下盛行西南偏南气流的日变化特征具有较强的预报能力。系统预报的14:00边界层顶高度与评估时段内实际对流边界层高度的变化趋势一致。但预报的对流边界层顶偏高,这与BJ-RUC系统采用YSU边界层参数化方案的垂直混合更强有关。 相似文献
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使用WRF中尺度数值模式, 分别选用两种不同的边界层参数化方案 (MYJ, YSU) 和3种陆面参数化方案 (SLAB, Noah, RUC), 对2004年7月1日08:00—7月4日20:00 (北京时) 北京地区夏季边界层结构进行1 km的高分辨模拟。对比分析了近地面层风场、温度场以及边界层的日变化特征, 结果发现:WRF模式基本模拟出了北京夏季边界层的日变化特征; 在边界层方案中, MYJ方案描述的边界层结构较YSU方案合理; Noah陆面模式较好地反映了城市的热岛效应; 无降水时, 风速及边界层高度对于陆面过程不敏感, 而降水发生后, 陆面过程对于边界层结构的影响增大; 各方案模拟的城区风速明显偏大, 这是因为没有充分考虑城市建筑物的阻力作用。 相似文献
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湍流频散对边界层风廓线的影响 总被引：2，自引：0，他引：2
应用包括湍流粘性和频散的新的Reynolds平均动量方程，分析了边界层的垂直风速廓线，发现包含湍流频散的地面层的风速廓线对经典的风廓线指数规律有一个对数规律的修改；而且在不稳定层结下比在稳定层结下，湍流的频散效应更为显；在中性条件下，指数规律退化为对数规律并且Karman常数被另外一个常数所代替，而这个新常数也可以通过相似理论来获得。 相似文献
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Long-Term Mean Wind Profiles Based on Similarity Theory 总被引：1，自引：1，他引：0
We provide general forms for long-term mean wind profiles from similarity-based wind profiles, beginning with a probabilistic
adaptation of Monin–Obukhov similarity theory. We develop an analytical formulation for the stability distributions prevailing
in the atmospheric surface layer, which in turn facilitates the derivation of a long-term mean wind profile based on Monin–Obukhov
similarity theory. The modelled stability distributions exhibit good agreement with measurements from sites having different
local conditions. The long-term wind profile formulation is further extended to include the influence of the depth of the
atmospheric boundary layer (h), which becomes relevant for heights above h/3, and the resultant long-term ‘tall’ profile form also matches observations. 相似文献
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In considering the weak non-linear effect, and using the small parameter expansion method, the analyt-ical expressions of the wind distribution within PBL (planetary boundary layer) and the vertical velocity at the top of the PBL are obtained when the PBL is divided into three layers and different eddy transfer coefficients K are adopted for the three layers. The conditions of barotropy and neutrality for the PBL are extended to that of baroclinity and non-neutral stratification. An example of a steady circular vortex is used to display the characteristics of the horizontal wind within the PBL and the vertical velocity at the top of the PBL. Some new results have been obtained, indicating that the magnitude of the speed in the lower height calculated by the present model is larger than that by the model in which k is a constant within the whole boundary layer, for example, in the classical Ekman boundary layer model and the model by Wu (1984). The angle between the wind at the top of the PBL and the wind near the surface calculated by the present model is less than that calculated by the single K model. These results are in agreement with the observations. 相似文献
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We test a flexible, idealized mean wind profile for the loweratmosphere that can easily be matched to whatever windobservations may be available. Its intended function is to providea `best guess' wind profile from limited observations, e.g., foruse in dispersion models, and to this end, following earlierauthors, we have matched a Monin–Obukhov layer to a baroclinic Ekman layer.To demonstrate the flexibility of the two-layer wind profile, weoptimize its free parameters to provide best interpolative fits toa sample of multi-level wind profiles. These include model windprofiles extracted from the Canadian Global EnvironmentalMulti-scale weather model (GEM), as well as experimental profilesfrom the Wangara experiment, and from an over-ocean dispersionexperiment (LROD). In most cases the two-layer profile fit issatisfactory. 相似文献
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Jon Wieringa 《Boundary-Layer Meteorology》1989,47(1-4):85-110
Annual wind distributions from six masts are used to investigate the annual variability of hourly-average wind. A variability extremum occurs at the height where the average diurnal cycle of wind reverses its phase from a nocturnal minimum to a nocturnal maximum. A simple profile model shows that in non-complex terrain, this reversal height varies approximately between 50 m at coasts and 90 m inland. The Weibull distribution shape factor k has a maximum at the reversal height, and with decreasing height, k decreases approximately as a linear function of height. Therefore estimation of wind distribution shape from surface data is possible in the surface layer. In the upper PBL, however, such estimation is not very feasible, because no simple methods are available to estimate the reversal height from routine surface observations.Also: Dept. of Applied Physics, Technical University, Delft, Netherlands. 相似文献
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Comparing mixing-length models of the diabatic wind profile over homogeneous terrain 总被引：1，自引：0，他引：1
Alfredo Peña Sven-Erik Gryning Charlotte Bay Hasager 《Theoretical and Applied Climatology》2010,100(3-4):325-335
Models of the diabatic wind profile over homogeneous terrain for the entire atmospheric boundary layer are developed using mixing-length theory and are compared to wind speed observations up to 300 m at the National Test Station for Wind Turbines at Høvsøre, Denmark. The measurements are performed within a wide range of atmospheric stability conditions, which allows a comparison of the models with the average wind profile computed in seven stability classes, showing a better agreement than compared to the traditional surface-layer wind profile. The wind profile is measured by combining cup anemometer and lidar observations, showing good agreement at the overlapping heights. The height of the boundary layer, a parameter required for the wind profile models, is estimated under neutral and stable conditions using surface-layer turbulence measurements, and under unstable conditions based on the aerosol backscatter profile from ceilometer observations. 相似文献