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11.
E. Batchvarova S.-E. Gryning M. W. Rotach A. Christen 《Boundary-Layer Meteorology》2002,103(3):509-509
Authors Index
Author Index volume 103 相似文献12.
An Urban Surface Exchange Parameterisation for Mesoscale Models 总被引：9，自引：11，他引：9
A scheme to represent the impact of urban buildings on airflow in mesoscale atmospheric models is presented. In the scheme, the buildings are not explicitly resolved, but their effects on the grid-averaged variables are parameterised. An urban quarter is characterised by a horizontal building size, a street canyon width and a building density as a function of height. The module computes the impact of the horizontal (roof and canyon floor) and vertical (walls) surfaces on the wind speed, temperature and turbulent kinetic energy. The computation of the shortwave and longwave radiation, needed to compute the temperature of the urban surfaces, takes into account the shadowing and radiation trapping effects induced by the urban canyons. The computation of the turbulent length scales in the TKE equation is also modified to take into account the presence of the buildings.The parameterisation is introduced into a mesoscale model and tested in a bidimensional case of a city over flat terrain. The new parameterisation is shown to be able to reproduce the most important features observed in urban areas better than the traditional approach which is based only on the modification of the roughness length, thereby retaining the Monin–Obukhov similarity theory. The new surface exchange parameterisation is furthermore shown to have a strong impact on the dispersion characteristics of air pollutants in urban areas. 相似文献
13.
Mathias W. Rotach 《Boundary-Layer Meteorology》2001,99(3):379-410
14.
Haid Maren Gohm Alexander Umek Lukas Ward Helen C. Rotach Mathias W. 《Boundary-Layer Meteorology》2022,182(3):335-362
Boundary-Layer Meteorology - We present a comprehensive analysis of four south föhn events observed during the Penetration and Interruption of Alpine Foehn (PIANO) field campaign in the Inn... 相似文献
15.
Boundary layer characteristics and turbulent exchange mechanisms in highly complex terrain 总被引：2，自引：0，他引：2
Mathias W. Rotach Marco Andretta Pierluigi Calanca Andreas P. Weigel Alexandra Weiss 《Acta Geophysica》2008,56(1):194-219
The Mesoscale Alpine Programme’s Riviera project investigated the turbulence structure and related exchange processes in an
Alpine valley by combining a detailed experimental campaign with high-resolution numerical modelling. The present contribution
reviews published material on the Riviera Valley’s boundary layer structure and discusses new material on the near-surface
turbulence structure. The general conclusion of the project is that despite the large spatial variability of turbulence characteristics
and the crucial influence of topography at all scales, the physical processes can accurately be understood and modelled. Nevertheless,
many of the “text book characteristics” like the interaction between the valley and slope wind systems or the erosion of the
nocturnal valley inversion need reconsideration, at least for small non-ideal valleys like the Riviera Valley. The project
has identified new areas of research such as post-processing methods for turbulence variables in complex terrain and new approaches
for the surface energy balance when advection is non-negligible. The exchange of moisture and heat between the valley atmosphere
and the free troposphere is dominated by local “secondary” circulations due to the curvature of the valley axis. Because many
curved valleys exist, and operational models still have rather poor resolution, parameterization of these processes may be
required. 相似文献
16.
Boundary-Layer Meteorology - When wind blows over the ocean, short wind-waves (of wavelength smaller than 10 m) are generated, rapidly reaching an equilibrium with the overlying turbulence (at... 相似文献
17.
On the turbulence structure in the stable boundary layer over the Greenland ice sheet 总被引：2，自引：1，他引：1
Turbulence measurements from a 30 m tower in the stably stratifiedboundary layer over the Greenland ice sheet are analyzed. The observationsinclude profile and eddy-correlation measurements at various levels. Atfirst, the analysis of the turbulence data from the lowest level (2 m aboveground) shows that the linear form of the non-dimensional wind profile(m) is in good agreement with the observations for z/L <0.4, whereL represents the Obukhov length. A linear regression yieldsm=1+5.8z/L. The non-dimensional temperature profile (h) at the2m level shows no tendency to increase with increasing stability. The datafrom the upper levels of the tower are analyzed in terms of both localscaling and surface-layer scaling. The m and the h values show atendency to level off at large stability (z/>0.4) where represents the local Obukhov length. Hence, the linear form of the functions is no longer appropriate under such conditions. The bestcorrespondence to the data can be achieved when using the expression ofBeljaars and Holtslag for m and h. The vertical profiles of theturbulent fluxes, the wind velocity variances and temperature variance arealso determined. The momentum flux profile and the profiles of wind speedvariances are in general agreement with other observations if a welldeveloped low-level wind maximum occurs, and the height of this maximum isused as a height scale. 相似文献
18.
A new scaling approach, based on the convective velocity obtained from the sun-exposed eastern slopes and thus suited for
steep and narrow Alpine valleys, is investigated with respect to pollutant dispersion. The capability of the new method is
demonstrated with the operational emergency response system of MeteoSwiss, which consists of the COSMO (COnsortium for Small-scale
MOdelling) numerical weather prediction model coupled with a Lagrangian particle dispersion model (LPDM). The new scaling
approach is introduced to the interface between COSMO and LPDM, and is compared to results of a classical similarity theory
approach and to the operational coupling type, which uses the turbulent kinetic energy (TKE) from the COSMO model directly.
For the validation of the modelling system, the TRANSALP-89 tracer experiment is used, which was conducted in highly complex
terrain in southern Switzerland. The ability of the COSMO model to simulate the valley wind system is assessed with several
meteorological surface stations, and the dispersion simulation is evaluated with the measurements from 25 surface samplers.
The sensitivity of the modelling system towards the soil moisture, horizontal grid resolution, and boundary-layer height determination
is investigated, and it is shown that, if the flow field is correctly reproduced, the new scaling approach improves the tracer
concentration simulation when compared to classical coupling methods. 相似文献
19.
R. Vogt A. Christen M. W. Rotach M. Roth A. N. V. Satyanarayana 《Theoretical and Applied Climatology》2006,84(1-3):117-126
Summary In Summer 2002 eddy covariance flux measurements of CO2 were performed over a dense urban surface. The month-long measurements were carried out in the framework of the Basel Urban
Boundary Layer Experiment (BUBBLE). Two Li7500 open path analysers were installed at z/zH = 1.0 and 2.2 above a street canyon with zH the average building height of 14.6 m and z the height above street level. Additionally, profiles of CO2 concentration were sampled at 10 heights from street level up to 2 zH. The minimum and maximum of the average diurnal course of CO2 concentration at 2 zH were 362 and 423 ppmv in late afternoon and early morning, respectively. Daytime CO2 concentrations were not correlated to local sources, e.g. the minimum occurred together with the maximum in traffic load.
During night-time CO2 is in general accumulated, except when inversion development is suppressed by frontal passages. CO2 concentrations were always decreasing with height and correspondingly, the fluxes – on average – always directed upward.
At z/zH = 2.2 low values of about 3 μmol m−2 s−1 were measured during the second half of the night. During daytime average values reached up to 14 μmol m−2 s−1. The CO2 fluxes are well correlated with the traffic load, with their maxima occurring together in late afternoon. Daytime minimum
CO2 concentrations fell below regional background values. Besides vertical mixing and entrainment, it is suggested that this
is also due to advection of rural air with reduced CO2 concentration. Comparison with other urban observations shows a large range of differences among urban sites in terms of
both CO2 fluxes and concentrations.
Present affiliation: Swiss Federal Office for Meteorology and Climatology, MeteoSwiss, Zürich, Switzerland 相似文献
20.
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