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1.
A model of the planetary boundary layer over a snow surface has been developed. It contains the vertical heat exchange processes due to radiation, conduction, and atmospheric turbulence. Parametrization of the boundary layer is based on similarity functions developed by Hoffert and Sud (1976), which involve a dimensionless variable, ζ, dependent on boundary-layer height and a localized Monin-Obukhov length. The model also contains the atmospheric surface layer and the snowpack itself, where snowmelt and snow evaporation are calculated. The results indicate a strong dependence of surface temperatures, especially at night, on the bursts of turbulence which result from the frictional damping of surface-layer winds during periods of high stability, as described by Businger (1973). The model also shows the cooling and drying effect of the snow on the atmosphere, which may be the mechanism for air mass transformation in sub-Arctic regions. 相似文献
2.
A mesoscale atmospheric numerical model is coupled with a physically based snow-pack model and with a snow-drift model. The snow model is verified for the French Alps by comparing its simulations to observations performed at the Col de Porte in the Chartreuse Massif. The snow erosion threshold depends on snow-pack properties such as density, dendricity, sphericity and particle size. The atmospheric turbulence scheme is modified in order to take into account stabilization effects due to airborne blown snow particles. In particular, vertically integrated stability functions for the stable boundary layer are completed by including the threshold friction velocity for snow erosion. The snow-drift model is calibrated by simulating the conditions observed during the Byrd snow project, held in West Antarctica in 1962. Finally, sensitivity experiments to the snow-surface properties show the importance of their accurate representation when modelling the contribution of deflation to the Antarctic surface mass balance. 相似文献
3.
Numerical Simulation Experiment of Land Surface Physical Processes and Local Climate Effect in Forest Underlying Surface 总被引：1，自引：0，他引：1 
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下载免费PDF全文 LIU Shuhu PAN Ying DENG Yi MA Mingmin JIANG Haimei LIN Hongtao JIANG Haoyu LIANG Fuming LIU Heping WANG Jianhua 《Acta Meteorologica Sinica》2006,20(1):72-85
Based on the basic principles of atmospheric boundary layer and plant canopy micrometeorology, a forest underlying surface land surface physical process model and a two-dimensional atmospheric boundary layer numerical model are developed and numerical simulation experiments of biosphere and physiological processes of vegetation and soil volumetric water content have been done on land surface processes with local climate effect. The numerical simulation results are in good agreement with realistic observations, which can be used to obtain reasonable simulations for diurnal variations of canopy temperature, air temperature in canopy, ground surface temperature, and temporal and spatial distributions of potential temperature and vertical wind velocity as well as relative humidity and turbulence exchange coefficient over non-homogeneous underlying surfaces. It indicates that the model developed can be used to study the interaction between land surface process and atmospheric boundary layer over various underlying surfaces and can be extended to local climate studies. This work will settle a solid foundation for coupling climate models with the biosphere. 相似文献
4.
S.D. Wright 《Boundary-Layer Meteorology》1998,89(2):175-195
The adaptation of the atmospheric boundary layer to a change in the underlying surface roughness is an interesting problem and hence much research, theoretical, experimental, and numerical, has been undertaken. Within the atmospheric boundary layer an accurate numerical model for the turbulent properties of the atmospheric boundary layer needs to be implemented if physically realistic results are to be obtained. Here, the adaptation of the atmospheric boundary layer to a change in surface roughness is investigated using a first-order turbulence closure model, a one-and-a-half-order turbulence closure model and a second-order turbulence closure model. Perturbations to the geostrophic wind and the pressure gradients are included and it is shown that the second-order turbulence closure model, namely the standard k - model, is inferior to a lower-order closure model if a modification to limit the turbulent eddy size within the atmospheric boundary layer is not included within the model. 相似文献
5.
M. W. Rotach R. Vogt C. Bernhofer E. Batchvarova A. Christen A. Clappier B. Feddersen S.-E. Gryning G. Martucci H. Mayer V. Mitev T. R. Oke E. Parlow H. Richner M. Roth Y.-A. Roulet D. Ruffieux J. A. Salmond M. Schatzmann J. A. Voogt 《Theoretical and Applied Climatology》2005,81(3-4):231-261
Summary The Basel UrBan Boundary Layer Experiment (BUBBLE) was a year-long experimental effort to investigate in detail the boundary layer structure in the City of Basel, Switzerland. At several sites over different surface types (urban, sub-urban and rural reference) towers up to at least twice the main obstacle height provided turbulence observations at many levels. In addition, a Wind Profiler and a Lidar near the city center were profiling the entire lower troposphere. During an intensive observation period (IOP) of one month duration, several sub-studies on street canyon energetics and satellite ground truth, as well as on urban turbulence and profiling (sodar, RASS, tethered balloon) were performed. Also tracer experiments with near-roof-level release and sampling were performed. In parallel to the experimental activities within BUBBLE, a meso-scale numerical atmospheric model, which contains a surface exchange parameterization, especially designed for urban areas was evaluated and further developed. Finally, the area of the full-scale tracer experiment which also contains several sites of other special projects during the IOP (street canyon energetics, satellite ground truth) is modeled using a very detailed physical scale-model in a wind tunnel. In the present paper details of all these activities are presented together with first results. 相似文献
6.
森林下垫面陆面物理过程及局地气候效应的数值模拟试验 总被引：5，自引：0，他引：5
文中基于大气边界层和植被冠层微气象学基本原理 ,建立了一个森林植被效应的陆面物理过程和二维大气边界层数值模式。并应用该模式进行了植被和土壤含水量等生物和生理过程在陆面过程和局地气候效应方面的数值模拟试验。所得数值模拟试验结果与实际情况相吻合。结果表明 ,应用该模式可获得植被温度、植被冠层内空气温度、地表温度日变化特征 ;森林下垫面大气边界层风速、位温、比湿、湍流交换系数的时空分布和日变化特征。该模式还可应用于不同下垫面 ,模拟陆面物理过程与大气边界层相互作用机制及其局地气候效应的研究 ,这将为气候模式与生物圈的耦合研究奠定一个良好的基础。 相似文献
7.
This paper uses a Modified Soil-Plant-Atmosphere Scheme (MSPAS) to study the interaction betweenland surface and atmospheric boundary layer processes. The scheme is composed of two main parts:atmospheric boundary layer processes and land surface processes. Compared with SiB and BATS, which arefamous for their detailed parameterizations of physical variables, this simplified model is more convenientand saves much more computation time. Though simple, the feasibility of the model is well proved inthis paper. The numerical simulation results from MSPAS show good agreement with reality. The schemeis used to obtain reasonable simulations for diurnal variations of heat balance, potential temperature ofboundary layer, and wind field, and spatial distributions of temperature, specific humidity, vertical velocity,turbulence kinetic energy, and turbulence exchange coefficient over desert and oasis. In addition, MSPAS isused to simulate the interaction between desert and oasis at night, and again it obtains reasonable results.This indicates that MSPAS can be used to study the interaction between land surface processes and theatmospheric boundary layer over various underlying surfaces and can be extended for regional climate andnumerical weather prediction study. 相似文献
8.
为研究不同人为热源引入方案对城市边界层结构模拟性能的影响，以杭州地区为例，在区域边界层模式（RBLM）中引入一种新人为热源处理方案，即对城市中的人为热排放分层考虑，将低层的人为热源加入地表能量平衡方程，将高层人为热源分布与建筑物高度和密度联系起来，加入热量方程中，同时考虑了人为热源强度的日变化。数值试验结果表明，这是一种比较合理的处理方案。人为热源引入方案对城市边界层结构的影响表现在:气温、湍流动能增加，并通过湍流交换输送到较高层大气；大气不稳定度增加，混合层高度最高抬升了400 m；城市地区上升速度增加，热岛环流加强；白天人为热源一般为太阳辐射的10%～20%，对地气交换的影响较小。夜间没有了太阳辐射能量，对地气交换的影响比日间更明显；冬季低层湍流活动加强，湍能约增加40%，大气层结稳定度降低。 相似文献
9.
Large eddy simulation has encountered difficulties in handling turbulence in the atmospheric surface layer due to deficiencies in sub-grid scale models. This paper addresses the possibility of resolving the turbulence in the upper part of the surface layer by a low-aspect ratio of grid spacing. Results show that resolved-scale shear stresses dominate over the sub-grid scale components so that effects due to the sub-grid scale model can be ignored in this region. The effects of the lower boundary condition on the resolved-scale turbulence in the upper part of the surface layer are discussed. It is concluded that the normalized mean velocity shear and resolved turbulence in the upper part of the surface layer are not affected by the specification of the lower boundary condition. In addition, the present work proposes a new independent model parameter, the Smagorinsky Reynolds Number (ReSM), and demonstrates that this number determines the resolved turbulence in the upper part of the surface layer. 相似文献
10.
11.
深凹地形边界层风场与湍流场结构及扩散规律的数值研究 总被引：1，自引：0，他引：1
建立了一个模拟小尺度复杂地形边界层平均流场和湍流场结构分布特征的三维非静力细网格高阶矩湍流闭合模式,并将此模式与一个拉格朗日粒子随机游动大气扩散数值模式相联结,以边界层气象模式的输出作为扩散模式的输入,构成了一个大气扩和模拟系统,成功地模拟了某地实际深凹露天矿区和理想凹坑地形两种情况下的平均流场、雷诺应力和湍流通量场,分析了其分布特征,并模拟了矿坑内污染物的散布规律 相似文献
12.
在非局地闭合大气边界层模拟研究基础上,选取黑河实验研究资料（HEIFE）,利用二维模式对绿洲和沙漠交界地区的内边界层结构进行了模拟研究,模式考虑了两种下垫面条件下动力、热力特性的不同,并加入了湿度及水汽通量的预报。模拟结果表明:二维非局地闭合模式能得到合理的TIBL结构的基本特征,包括平均场、湍流场等,并能模拟给出一些由下垫面特性形成的大气现象,如沙漠地区逆湿现象的生消过程、绿洲的冷岛效应、绿洲与沙漠因热力差异而形成的局部环流形势等细致结构,符合沙漠站白天观测事实的典型特征。 相似文献
13.
A set of global atmospheric simulations has been performed with the ARPEGE-Climat model in order to quantify the contribution of realistic snow conditions to seasonal atmospheric predictability in addition to that of a perfect sea surface temperature (SST) forcing. The focus is on the springtime boreal hemisphere where the combination of a significant snow cover variability and an increasing solar radiation favour the potential snow influence on the surface energy budget. The study covers the whole 1950?C2000 period through the use of an original snow mass reanalysis based on an off-line land surface model and possibly constrained by satellite snow cover observations. Two ensembles of 10-member AMIP-type experiments have been first performed with relaxed versus free snow boundary conditions. The nudging towards the monthly snow mass reanalysis significantly improves both potential and actual predictability of springtime surface air temperature over Central Europe and North America. Yet, the impact is confined to the lower troposphere and there is no clear improvement in the predictability of the large-scale atmospheric circulation. Further constraining the prescribed snow boundary conditions with satellite observations does not change much the results. Finally, using the snow reanalysis only for initializing the model on March 1st also leads to a positive impact on predicted low-level temperatures but with a weaker amplitude and persistence. A conditional skill approach as well as some selected case studies provide some guidelines for interpreting these results and suggest that an underestimated snow cover variability and a misrepresentation of ENSO teleconnections may hamper the benefit of an improved snow initialization in the ARPEGE-Climat model. 相似文献
14.
苏州东山冬季大气边界层结构特征及其对污染物浓度的影响 总被引：5，自引：1，他引：5
利用2015年1月15—27日在苏州东山气象观测站系留气艇观测数据以及细颗粒物浓度观测资料,对东山大气边界层结构特征及其对污染物垂直结构分布的影响进行分析研究。结果表明:苏州东山地区冬季空气污染过程的边界层结构演变比较典型,夜间稳定边界层高度约为200 m,白天最大边界层高度可达1 000 m。边界层内污染物垂直结构分布易受边界层高度的影响,较低的大气边界层高度可使细颗粒物在近地层持续累积;反之,边界层高度较高,湍流发展旺盛,颗粒物垂直分布均匀。夜间大气边界层稳定,逆温结构多发,导致近地面出现细颗粒物堆积。风的垂直结构对细颗粒物空间分布也存在显著影响,在风速较小的低空层细颗粒分布较多,而风速较大的中高层的分布较少。 相似文献
15.
In this paper, we consider boundary-layer effects on atmospheric fronts. For this purpose we developed a dry, hydrostatic, two-dimensional numerical model with turbulence parameterized with the 1/2 -order eddy viscosity closure of Mellor and Yamada. In the surface layer we use Monin–Obukhov similarity and there is an interactive soil model to obtain lower boundary conditions for the atmospheric model. First, effects of turbulence are studied without thermal forcing at the surface and comparisons are made between inviscid and turbulent conditions. Sensitivity studies with respect to surface roughness are also performed. Subsequently we study effects of surface thermal forcing on fronts. The results show that, during summer, fronts display strong diurnal variation. Vertical velocities increase significantly during the day while gradients in temperature and vorticity across the front strengthen in the evening and at night. In winter the diurnal variation is much less pronounced. We attempt to find physical mechanisms responsible for such frontal behaviour and we compare our results with available observations. 相似文献
16.
大气边界层阵风相干结构的产生条件 总被引：1，自引：0，他引：1
壁湍流相干结构的发现是近代湍流研究的重大进展之一,从20世纪50年代开始,在大气边界层湍流中也发现了相干结构——对流云街,并进行了系统的研究。近些年来,人们发现在近地层湍流中也存在相干结构。利用北京325 m气象塔对城市下垫面中大风和小风天气的风速分析,发现较有规律的周期3~6 min的阵风,且有明显的相干结构,而对不同下垫面的阵风研究,均发现存在这种相干结构,这种阵风相干结构对通量输送有不可忽视的作用。本文利用2012年4月甘肃省民勤县巴丹吉林沙漠观测塔的超声风速和平均场风速、温度观测资料,对阵风相干结构的产生条件进行了分析。采用傅立叶变换,将三维超声风速按频率分成基流(周期10分钟以上)、阵风扰动(周期1到10分钟)、湍流脉动(周期小于1分钟)三部分,结合平均场的资料分析发现:阵风相干结构出现在静力中性、不稳定甚至略微稳定的条件下,或者说机械作用主导的大气边界层,阵风区就会出现相干结构,热力作用对其有抑制和干扰的作用。从而,阵风的相干结构和壁面相干结构都出现在中性条件下,是机械湍流的现象,都主导着动量能量的输运。阵风区的相干结构并不等同于对流云街,他们出现在不同的大气稳定度条件下且尺度不同。 相似文献
17.
Note on turbulence statistics in z-less stratification 总被引：1，自引：0，他引：1
Jinkyu Hong 《Asia-Pacific Journal of Atmospheric Sciences》2010,46(1):113-117
In boundary layer meteorology, surface layer similarity theory plays a critical role in measuring and modeling biospheric fluxes. In stable boundary layer, surface layer similarity called z-less stratification has been one of main research topics for over than two decades and the issue has yet to be settled in micrometeorology. In this scientific discussion on z-less turbulence, different turbulence statistics were used inconsistently and it was argued that z-less turbulence was valid if only any turbulence statistics were constant with different atmospheric stabilities. Consequently, such inconsistently tested turbulence statistics and misconception on z-less turbulence hinder us from correctly understanding turbulence structure in the stable boundary layer. This note revisits z-less turbulence and emphasizes that different dimensionless turbulence statistics generally do not exhibit a common behavior in the limit of z-less stratification. 相似文献
18.
Impact of the Diurnal Cycle of the Atmospheric Boundary Layer on Wind-Turbine Wakes: A Numerical Modelling Study 总被引：1，自引：1，他引：0
The wake characteristics of a wind turbine for different regimes occurring throughout the diurnal cycle are investigated systematically by means of large-eddy simulation. Idealized diurnal cycle simulations of the atmospheric boundary layer are performed with the geophysical flow solver EULAG over both homogeneous and heterogeneous terrain. Under homogeneous conditions, the diurnal cycle significantly affects the low-level wind shear and atmospheric turbulence. A strong vertical wind shear and veering with height occur in the nocturnal stable boundary layer and in the morning boundary layer, whereas atmospheric turbulence is much larger in the convective boundary layer and in the evening boundary layer. The increased shear under heterogeneous conditions changes these wind characteristics, counteracting the formation of the night-time Ekman spiral. The convective, stable, evening, and morning regimes of the atmospheric boundary layer over a homogeneous surface as well as the convective and stable regimes over a heterogeneous surface are used to study the flow in a wind-turbine wake. Synchronized turbulent inflow data from the idealized atmospheric boundary-layer simulations with periodic horizontal boundary conditions are applied to the wind-turbine simulations with open streamwise boundary conditions. The resulting wake is strongly influenced by the stability of the atmosphere. In both cases, the flow in the wake recovers more rapidly under convective conditions during the day than under stable conditions at night. The simulated wakes produced for the night-time situation completely differ between heterogeneous and homogeneous surface conditions. The wake characteristics of the transitional periods are influenced by the flow regime prior to the transition. Furthermore, there are different wake deflections over the height of the rotor, which reflect the incoming wind direction. 相似文献
19.
非均匀网格的过渡湍流理论及其在大气边界层数值模拟中的应用 总被引：1，自引：1，他引：1
本文将Stull提出的均匀网格下的过渡湍流理论推广到非均匀网格情形，推广的非均匀网格的过渡湍流理论满足Stull提出的对过渡矩阵系数的要求并具有清晰的物理意义。然后，将非均匀网格的过渡湍流理论应用于一维大气边界层数值模式中，对Wangara资料进行了模拟，并与均匀网格情形进行了对比。计算表明，非均匀网格的过渡湍流模式能很好地模拟Wangara大气边界层平均量与湍流量的变化；本文非均匀网格的过渡湍流理论的推广是可行的，它可能会在大气边界层数值模拟及其他方面（如：中尺度模式）得到应用。 相似文献
20.
The dispersion of heavy particles subjected to a turbulent forcing is often simulated with Lagrangian stochastic models. Although
these models have been employed successfully over land, the implementation of traditional LS models in the marine boundary
layer is significantly more challenging. We present an adaptation of traditional Lagrangian stochastic models to the atmospheric
marine boundary layer with a particular focus on the representation of the scalar turbulence for temperature and humidity.
In this new model, the atmosphere can be stratified and the bottom boundary is represented by a realistic wavy surface that
moves and deforms. Hence, the correlation function for the turbulent flow following a particle is extended to the inhomogenous,
anisotropic case. The results reproduce behaviour for scalar Lagrangian turbulence in a stratified airflow that departs only
slightly from the expected behaviour in isotropic turbulence. When solving for the surface temperature and the radius of evaporating
heavy water droplets in the airflow, the modelled turbulent forcing on the particle also behaves remarkably well. We anticipate
that this model will prove especially useful in the context of sea-spray dispersion and its associated sensible heat, latent
heat, and gas fluxes between spray droplets and the atmosphere. 相似文献