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1.
Two levels of triple-hot-film and sonic anemometers were deployed on a 5.5-m towerduring the Cooperative Atmospheric Surface Exchange Study (CASES-99) in October1999. Each triple-hot-film probe was collocated 50 mm from the sonic sensing path ona common boom. Various problems with using triple-hot-films in the atmosphere toresolve wind components are addressed including the derivation of a yaw angle correction using the collocated sensors. It was found that output voltage drift due to changes in environmental temperature could be monitored and corrected using an automated system. Non-unique solutions to heat transfer equations can be resolved using a collocated sonic anemometer. Multi-resolution decomposition of the hot-film data was used to estimate appropriate day and night averaging periods for turbulent flux measurements in and near the roughness sub-layer. Finally, triple-hot-film measurements of mean wind magnitude (M), turbulent kinetic energy (TKE), sensible heat flux (H), and local friction velocity (u*) are compared to those of the collocated CSAT3 sonic anemometers. Overall, the mean wind magnitudes measured by the triple-hot-film and the collocated sonic sensorswere close, consistent and independent of stability or proximity to the ground. The turbulent statistics, TKE, u*, and H, measured by the two sensor systems were reasonably close together at z = 5 m. However, the ratio of sonic measurement/hot-film measurement decreased toward the ground surface, especially during stable conditions. 相似文献
2.
Large eddy simulation and study of the urban boundary layer 总被引：7，自引：1，他引：6
3.
MM5模式中城市冠层参数化方案的设计及其数值试验 总被引：15，自引：5，他引：15
文中在综合国外一些较先进的中尺度模式城市作用参数化方案的基础上 ,从城市下垫面结构对城市边界层大气作用的物理机制及实际应用两方面出发 ,对城市下垫面结构和人为活动等因素对边界层结构的影响及中尺度模式中城市化作用的合理体现等问题进行了较全面的考虑 ,改进和设计出能够较全面、细致地描述城市结构对大气边界层动力、热力结构的影响 ,且适合中尺度模式结构特点的城市冠层参数化方案 (UCP) ,并实现了其与MM5模式的耦合。进行了耦合后的UCP方案及采用原城市作用方案的MM5模式对BECAPEX试验期间北京地区气象条件多重嵌套细尺度进行了模拟试验 ,并与观测结果对比 ,结果表明 :相比于MM 5模式中原有表示城市作用的参数化方案来讲 ,设计的UCP方案在很大程度上提高了MM 5模式对城市边界层热力和动力结构的模拟能力。 相似文献
4.
Full-scale observations from two urban sites in Basel, Switzerland were analysed to identify the magnitude of different processes
that create, relocate, and dissipate turbulent kinetic energy (TKE) in the urban atmosphere. Two towers equipped with a profile
of six ultrasonic anemometers each sampled the flow in the urban roughness sublayer, i.e. from street canyon base up to roughly
2.5 times the mean building height. This observational study suggests a conceptual division of the urban roughness sublayer
into three layers: (1) the layer above the highest roofs, where local buoyancy production and local shear production of TKE
are counterbalanced by local viscous dissipation rate and scaled turbulence statistics are close to to surface-layer values;
(2) the layer around mean building height with a distinct inflexional mean wind profile, a strong shear and wake production
of TKE, a more efficient turbulent exchange of momentum, and a notable export of TKE by transport processes; (3) the lower
street canyon with imported TKE by transport processes and negligible local production. Averaged integral velocity variances
vary significantly with height in the urban roughness sublayer and reflect the driving processes that create or relocate TKE
at a particular height. The observed profiles of the terms of the TKE budget and the velocity variances show many similarities
to observations within and above vegetation canopies. 相似文献
5.
Intercomparison of Planetary Boundary-Layer Parametrizations in the WRF Model for a Single Day from CASES-99 总被引：11，自引：6，他引：5
This study compares five planetary boundary-layer (PBL) parametrizations in the Weather Research and Forecasting (WRF) numerical
model for a single day from the Cooperative Atmosphere-Surface Exchange Study (CASES-99) field program. The five schemes include
two first-order closure schemes—the Yonsei University (YSU) PBL and Asymmetric Convective Model version 2 (ACM2), and three
turbulent kinetic energy (TKE) closure schemes—the Mellor–Yamada–Janjić (MYJ), quasi-normal scale elimination (QNSE), and
Bougeault–Lacarrére (BouLac) PBL. The comparison results reveal that discrepancies among thermodynamic surface variables from
different schemes are large at daytime, while the variables converge at nighttime with large deviations from those observed.
On the other hand, wind components are more divergent at nighttime with significant biases. Regarding PBL structures, a non-local
scheme with the entrainment flux proportional to the surface flux is favourable in unstable conditions. In stable conditions,
the local TKE closure schemes show better performance. The sensitivity of simulated variables to surface-layer parametrizations
is also investigated to assess relative contributions of the surface-layer parametrizations to typical features of each PBL
scheme. In the surface layer, temperature and moisture are more strongly influenced by surface-layer formulations than by
PBL mixing algorithms in both convective and stable regimes, while wind speed depends on vertical diffusion formulations in
the convective regime. Regarding PBL structures, surface-layer formulations only contribute to near-surface variability and
then PBL mean properties, whereas shapes of the profiles are determined by PBL mixing algorithms. 相似文献
6.
Very few attempts have so far been made to quantify the momentum and turbulent kinetic energy (TKE) budgets within real urban
canopies. In this study, sonic anemometer data obtained during the Joint Urban 2003 field campaign in Oklahoma City, U.S.A.
were used for calculating the momentum and TKE budgets within a real-world urban street canyon. Sonic anemometers were deployed
on multiple towers in the lower half of the canyon. Gradients in all three principal directions were included in the analyses.
The storage and buoyancy terms were found to have negligible contributions to both the momentum and TKE budgets. The momentum
budgets were generally found to be more complex than a simple balance of two physical processes. The horizontal terms were
found to have significant and sometimes dominant contributions to the momentum and TKE budgets. 相似文献
7.
湍流能量（TKE）闭合方案是近年来大气边界层（PBL）模式中技推崇的方法,它具有11－2阶精度。大气环流模式的计算容量和垂直网络限制,不允许PBL方案过份精细。本文对TKE方案进行简化及网络稀疏化试验。并用Wangara资料验证。验证结果表明：此方案引入PBL内仅设置5层的大气环流模式是可行的。地面以上400米内模式结果与实测吻合。但中、上部位温计算值偏高。关于本方案在大尺度模式中的应用尚须进一步研究。 相似文献
8.
Evidence of Organized Large Eddies by Ground-Based Doppler Lidar, Sonic Anemometer and Sodar 总被引：3，自引：0，他引：3
Philippe Drobinski Robert a. Brown Pierre H. Flamant Jacques Pelon 《Boundary-Layer Meteorology》1998,88(3):343-361
In an experiment investigating the planetary boundary layer (PBL) wind and temperature fields, and PBL inversion height recorded by various instruments, the results reveal the presence of organized large eddies (OLE) or rolls. The measurements by lidars, anemometers, soundings and sodar gave an overview of the characteristics of the rolls and sources of energy production that maintain them. The experimental results obtained on two consecutive days are compared to model outputs. The agreement is excellent, showing that thermal stratification and wind shear are important factors in the structure and dynamics of OLE. A heterodyne Doppler lidar (HDL) is shown to be a useful tool in the study of OLE. 相似文献
9.
An attempt is made to study the planetary boundary layer (PBL) characteristics during the winter period at Anand (22.4°N, 72.6°E), a semi-arid region, which is located in the western part of India. A one-dimensional turbulent kinetic energy (TKE) closure model is used for the study. The structure of the PBL,which consists of profiles of zonal and meridional components of wind,potential temperature and specific humidity, is simulated. A one-dimensional soil heat and moisture transport parameterization scheme is incorporated for the accurate representation of the energy exchange processes at the soil-atmosphere interface. The diurnal variation of fluxes of sensible heat, latent heat, shortwave radiation, net radiation and soil flux, soil temperature at different depths, Richardson number and TKE at the height of the constant flux layer is studied. The model predictions are compared with the available observations obtained from a special Land Surface Processes (LSP) experiment. 相似文献
10.
利用WRF模式结合不同的边界层参数化方案,对2007年7月3—5日发生在江淮流域的一次梅雨锋暴雨过程进行多组数值模拟试验。结果发现,边界层方案的选取对于降水的落区和强度模拟会产生较显著的影响;在降水率及地面要素的模拟上,各方案在降水中后期的模拟差异明显大于降水发生阶段;不同边界层方案的选取对于降水时段内的水平风场、垂直运动和假相当位温的垂直分布都产生影响,直接影响降水时空分布的模拟;不同方案都模拟出了在降水发生之后不同于晴空日变化的湍流动能垂直分布,经分析发现与局地较强的垂直风切变和近地面强湍流气团被抬升有关,而浮力项起着耗散作用;各方案的湍流交换特征与湍流动能特征基本吻合,相比于其他方案,MYJ方案在降水区域的湍流动能及湍流交换强度明显偏弱,对热通量的输送也偏弱;GBM方案在边界层内的湍流混合偏弱而在边界层以上湍流混合显著偏强,热通量输送在边界层以上的高度上误差明显,影响了对降水区域气象要素的模拟能力,仍需要进一步改进。 相似文献
11.
Youngseob Kim Karine Sartelet Jean-Christophe Raut Patrick Chazette 《Boundary-Layer Meteorology》2013,149(1):105-132
Meteorological modelling in the planetary boundary layer (PBL) over Greater Paris is performed using the Weather Research and Forecast (WRF) numerical model. The simulated meteorological fields are evaluated by comparison with mean diurnal observational data or mean vertical profiles of temperature, wind speed, humidity and boundary-layer height from 6 to 27 May 2005. Different PBL schemes, which parametrize the atmospheric turbulence in the PBL using different turbulence closure schemes, may be used in the WRF model. The sensitivity of the results to four PBL schemes (two non-local closure schemes and two local closure schemes) is estimated. Uncertainties in the PBL schemes are compared to the influence of the urban canopy model (UCM) and the updated Coordination of Information on the Environment (CORINE) land-use data. Using the UCM and the CORINE land-use data produces more realistic modelled meteorological fields. The wind speed, which is overestimated in the simulations without the UCM, is improved below 1,000 m height. Furthermore, the modelled PBL heights during nighttime are strongly modified, with an increase that may be as high as 200 %. At night, the impact of changing the PBL scheme is lower than the impact of using the UCM and the CORINE land-use data. 相似文献
12.
A TKE-dissipation model for the atmospheric boundary layer 总被引：1，自引：0，他引：1
Anders Andrén 《Boundary-Layer Meteorology》1991,56(3):207-221
The dissipation, , of turbulent kinetic energy (TKE) is a key parameter in atmospheric boundary-layer (ABL) models. Besides being a sink for momentum, it is often used together with the TKE to define an internal turbulence time scale for closure relations. A prognostic formulation for the dissipation of TKE is formulated, based on isotropic tensor modeling methods. The formulation is coupled to a level 2.5 second-order closure model and evaluated against measurements taken in horizontally homogeneous conditions, as well as against a tailored length-scale formulation. A formulation suitable for convective as well as neutral and stable ABLs is suggested.On leave from Department of Meteorology, Uppsala University, P.O. Box 516, S-751 20 Uppsala, Sweden.The National Center for Atmospheric Research is sponsored by the National Science Foundation. 相似文献
13.
A mesoscale planetary boundary layer (PBL) numerical model has been developed to study airflow over complex topography. Turbulence closures using the turbulent kinetic energy (TKE) and dissipation () equations are investigated in combination with the level 2.5 scheme of Mellor and Yamada (1982) to determine eddy diffusivities for momentum and heat. This modified E- closure is simpler than the level 3 one which requires more prognostic equations for moist turbulent transport.One-dimensional (1-D) model results show that the PBL mean flows under various stability conditions are not significantly sensitive to the modified Blackadar and Kolmogorov eddy mixing-length formulations used in this E- model, although the latter yields excessively large mixing lengths in the entrainment region of the upper PBL. Eddy mixing lengths in the Kolmogorov-type formulation can be better defined by introducing background dissipation. Using the same prognostic TKE equation, the 1-D model results are not significantly affected by different diagnostic formulations in the closures. The simulated results compare well with large-eddy simulations and those obtained using higher-order closure schemes including the level 3 one. The results are found to be insensitive to eddy Prandtl number, in contrast to the 2-D model results (see Part II). 相似文献
14.
The Coupling State of an Idealized Stable Boundary Layer 总被引：1，自引：1，他引：0
Otávio C. Acevedo Felipe D. Costa Gervásio A. Degrazia 《Boundary-Layer Meteorology》2012,145(1):211-228
The coupling state between the surface and the top of the stable boundary layer (SBL) is investigated using four different schemes to represent the turbulent exchange. An idealized SBL is assumed, with fixed wind speed and temperature at its top. At the surface, two cases are considered, first a constant temperature, 20 K lower than the SBL top, and later a constant 2 K h−1 cooling rate is assumed for 10 h after a neutral initial condition. The idealized conditions have been chosen to isolate the influence of the turbulence formulations on the coupling state, and the intense stratification has the purpose of enhancing such a response. The formulations compared are those that solve a prognostic equation for turbulent kinetic energy (TKE) and those that directly prescribe turbulence intensity as a function of atmospheric stability. Two TKE formulations are considered, with and without a dependence of the exchange coefficients on stability, while short and long tail stability functions (SFs) are also compared. In each case, the dependence on the wind speed at the SBL top is considered and it is shown that, for all formulations, the SBL experiences a transition from a decoupled state to a coupled state at an intermediate value of mechanical forcing. The vertical profiles of potential temperature, wind speed and turbulence intensity are shown as a function of the wind speed at the SBL top, both for the decoupled and coupled states. The formulation influence on the coupling state is analyzed and it is concluded that, in general, the simple TKE formulation has a better response, although it also tends to overestimate turbulent mixing. The consequences are discussed. 相似文献
15.
16.
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
17.
复杂地形上气象场对空气质量数值模拟
结果影响的研究 总被引：2，自引：2，他引：0
利用WRF模式三种边界层参数化方案(YSU、MYJ、ACM2)产生的气象场分别驱动多尺度空气质量模式CMAQ,对兰州市西固区冬季2005年1月27日至2月2日期间SO2和NO2浓度进行了数值模拟,将模拟结果与同期监测的污染物浓度进行对比分析,结果表明:WRF模式不同边界层参数化方案模拟输出的气象场驱动CMAQ模式所模拟的SO2和NO2浓度均可以反映出污染物的时空变化特征,CMAQ模式具有模拟复杂下垫面高分辨率污染物输送特征的能力;WRF模式的边界层参数化方案选为局地与非局地闭合方案(ACM2)时,模拟的气象场驱动CMAQ模式得到的空气污染物浓度分布特征最优,这主要是由于ACM2的湍流输送机制较为合理,模拟的边界层低层气象场更接近实际,从而可以较好地模拟污染物的输送特征;当CMAQ模式的垂直混合方案与WRF模式的湍流输送方案一致时(均采用ACM2方案),模式间的兼容性好. 相似文献
18.
The Role of Planetary Boundary-Layer Parameterizations in the Air Quality of an Urban Area with Complex Topography 总被引：3，自引：1，他引：2
Elizabeth Bossioli Maria Tombrou Aggeliki Dandou Eleni Athanasopoulou Kostas V. Varotsos 《Boundary-Layer Meteorology》2009,131(1):53-72
The effect of different planetary boundary-layer (PBL) parameterization schemes on the spatial distribution of atmospheric
pollution over the complex topography of the greater Athens area is investigated. Four PBL schemes originally implemented
in a numerical meteorological model and a fifth one simulating the urban effect are examined. Two different atmospheric conditions
are analyzed; a typical summer and a typical winter pollution episode. The relative importance of chemical and physical processes
of the pollution predictions is discussed using process analysis. It is revealed that, for primary pollutants, a local scheme
seems more adequate to represent the maximum observed concentrations while, completely different in structure, a non-local
scheme reproduces the mean observed values in the basin. Concerning secondary pollutants, peak concentration differences,
due to the different PBL schemes, are smoothed out. Nevertheless, the PBL scheme selection shapes the horizontal and the vertical
extension of maximum values. The non-local and semi non-local schemes are superior to the others, favouring strong vertical
mixing and transport towards the surface. The stronger turbulence accommodated effectively by the semi non-local urban scheme
enhances ozone production along the sea-breeze axis and preserves the high ozone concentrations during the nighttime hours
in the urban core. 相似文献
19.
Along-Coast Features of Bora-Related Turbulence 总被引：1，自引：1，他引：0
?eljko Ve?enaj Danijel Belu?i? Vanda Grubi?i? Branko Grisogono 《Boundary-Layer Meteorology》2012,143(3):527-545
The along-coast, offshore turbulence structure of the Bora flow that occurred on 7 November 1999 during the Mesoscale Alpine Programme (MAP) Intensive Observation Period 15 is examined. In this analysis we employ the aircraft and dropsonde data obtained over the Adriatic Sea, where the turbulence structure is determined by estimating turbulent kinetic energy (TKE) and its dissipation rate along the flight legs. The turbulence characteristics of Bora in the lee of the Dinaric Alps is greatly influenced by the mesoscale Bora flow structure over the Adriatic Sea, which in the cross-wind direction features an interchange of jets and wakes related to mountain gaps and peaks. In order to establish the origin of turbulence, the Weather Research and Forecasting—Advanced Research WRF (WRF-ARW) numerical model is used and its results are compared to the measurements. All five TKE-prediction parametrization schemes available in the model show reasonable agreement with the measured values. Since these parametrization schemes do not have horizontal advection included, they suggest that the along-flight structure of the Bora turbulence is principally generated by the local vertical wind shear. Further evidence is needed to support this hypothesis. 相似文献
20.
Based on some advanced urban parameterization schemes for mesoscale model,a new urban canopy parameterization (UCP) for MM5 is developed.The UCP takes into account the impacts of urban infrastructure and anthropogenic activity on the dynamic,thermal structures of urban surface layer and the urban surface energy budget in a more rational way according to conformation of MMS.The UCP is implemented in MM5 and validated by IOP data in 2001 winter BECAPEX and automatic meteorological station data in Beijing area.The results illustrate that UCP versus traditional urban parameterization in MM5,it can make MM5 reproduce main characteristics of winter UBL in Beijing,which include urban heat island and its diurnal evolvement,nocturnal elavated inversion in downtown area,and some dynamic stuctures such as TKE peak at the top of urban canopy,lower wind speed in urban surface layer and so on. 相似文献