ORCID Profile
0000-0001-6972-4371
Current Organisation
Monash University
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Interdisciplinary Engineering | Computational Fluid Dynamics | Infrastructure Engineering and Asset Management | Fluidisation and Fluid Mechanics
Oil and Gas Extraction | Expanding Knowledge in Engineering |
Publisher: Elsevier BV
Date: 06-1998
Publisher: American Geophysical Union (AGU)
Date: 10-1999
DOI: 10.1029/1999WR900197
Publisher: American Meteorological Society
Date: 09-2004
Publisher: American Geophysical Union (AGU)
Date: 05-1986
Publisher: American Geophysical Union (AGU)
Date: 11-1995
DOI: 10.1029/95WR00003
Publisher: American Geophysical Union (AGU)
Date: 16-07-2002
DOI: 10.1029/2002EO000225
Publisher: Copernicus GmbH
Date: 03-02-2011
Abstract: Abstract. A new method for measuring air temperature profiles in the atmospheric boundary layer at high spatial and temporal resolution is presented. The measurements are based on Raman scattering distributed temperature sensing (DTS) with a fiber optic cable attached to a tethered balloon. These data were used to estimate the height of the stable nocturnal boundary layer. The experiment was successfully deployed during a two-day c aign in September 2009, providing evidence that DTS is well suited for this atmospheric application. Observed stable temperature profiles exhibit an exponential shape confirming similarity concepts of the temperature inversion close to the surface. The atmospheric mixing height (MH) was estimated to vary between 5 m and 50 m as a result of the nocturnal boundary layer evolution. This value is in good agreement with the MH derived from concurrent Radon-222 (222Rn) measurements and in previous studies.
Publisher: American Geophysical Union (AGU)
Date: 11-11-2021
DOI: 10.1029/2021GL093746
Abstract: Taylor’s frozen turbulence hypothesis (FTH) is investigated in the roughness sublayer of a sloped vineyard canopy using a spatial array of fine‐wire thermocouples and ultrasonic anemometers. The Ellipse Approximation (EA) method is applied to the measured space‐time temperature correlation function to delineate sweeping effects from advection velocity. Sweeping effects are explained primarily by the turbulence kinetic energy. Upon the removal of sweeping effects, the advection velocity is found to be commensurate with the mean velocity.
Publisher: Springer Science and Business Media LLC
Date: 13-12-2012
Publisher: Cambridge University Press
Date: 21-10-2004
Publisher: American Meteorological Society
Date: 09-1996
Publisher: American Geophysical Union (AGU)
Date: 06-2006
DOI: 10.1029/2005WR004651
Publisher: American Meteorological Society
Date: 22-11-2013
Abstract: The flux of water vapor due to advection is measured using high-resolution Raman lidar that was orientated horizontally across a land–lake transition. At the same time, a full surface energy balance is performed to assess the impact of scalar advection on energy budget closure. The flux of water vapor due to advection is then estimated with analytical solutions to the humidity transport equation that show excellent agreement with the field measurements. Although the magnitude of the advection was not sufficient to account for the total energy deficit for this field site, the analytical approach is used to explore situations where advection would be the dominant transport mechanism. The authors find that advection is at maximum when the measurement height is 0.036 times the distance to a land surface transition. The framework proposed in this paper can be used to predict the potential impact of advection on surface flux measurements prior to field deployment and can be used as a data analysis algorithm to calculate the flux of water vapor due to advection from field measurements.
Publisher: Springer Paris
Date: 2012
Publisher: American Geophysical Union (AGU)
Date: 10-2000
DOI: 10.1029/2000WR900123
Publisher: American Geophysical Union (AGU)
Date: 06-2008
DOI: 10.1029/2007WR006361
Publisher: Elsevier BV
Date: 09-2011
Publisher: Elsevier BV
Date: 05-2013
Publisher: Elsevier BV
Date: 08-2017
Publisher: American Geophysical Union (AGU)
Date: 04-1993
DOI: 10.1029/93WR00094
Publisher: Elsevier BV
Date: 03-1992
Publisher: Elsevier BV
Date: 10-1999
Publisher: Elsevier BV
Date: 2013
Publisher: American Geophysical Union (AGU)
Date: 21-07-2004
DOI: 10.1029/2003JD004047
Publisher: American Geophysical Union (AGU)
Date: 09-2013
DOI: 10.1002/WRCR.20417
Publisher: Elsevier BV
Date: 05-2013
Publisher: American Geophysical Union (AGU)
Date: 12-1992
DOI: 10.1029/92WR01860
Publisher: Elsevier BV
Date: 02-1999
Publisher: Elsevier BV
Date: 11-2001
Publisher: American Geophysical Union (AGU)
Date: 2005
DOI: 10.1029/2004WR003899
Publisher: SPIE
Date: 06-10-2005
DOI: 10.1117/12.629376
Publisher: Springer Science and Business Media LLC
Date: 09-05-2009
Publisher: Elsevier BV
Date: 08-2002
Publisher: Springer Science and Business Media LLC
Date: 2000
Publisher: Springer Netherlands
Date: 1999
Publisher: Springer Science and Business Media LLC
Date: 10-1995
DOI: 10.1007/BF00615336
Publisher: Springer Science and Business Media LLC
Date: 06-1994
DOI: 10.1007/BF00613278
Publisher: Elsevier
Date: 1994
Publisher: Elsevier BV
Date: 07-2006
Publisher: American Geophysical Union (AGU)
Date: 09-2011
DOI: 10.1029/2011WR010529
Publisher: Elsevier BV
Date: 06-2008
Publisher: American Meteorological Society
Date: 10-2003
Publisher: Elsevier BV
Date: 11-1999
Publisher: Springer Science and Business Media LLC
Date: 07-2004
Publisher: American Geophysical Union (AGU)
Date: 1992
DOI: 10.1029/91WR02324
Publisher: Elsevier BV
Date: 08-1988
Publisher: American Geophysical Union (AGU)
Date: 02-2005
DOI: 10.1029/2005EO050009
Publisher: Elsevier BV
Date: 12-2008
Publisher: Springer Science and Business Media LLC
Date: 1995
DOI: 10.1007/BF00712392
Publisher: Wiley
Date: 04-03-2012
DOI: 10.1002/ECO.1257
Publisher: Springer Science and Business Media LLC
Date: 10-09-2009
Publisher: American Geophysical Union (AGU)
Date: 11-1994
DOI: 10.1029/94WR01673
Publisher: American Geophysical Union (AGU)
Date: 08-1992
DOI: 10.1029/92WR00705
Publisher: Springer Science and Business Media LLC
Date: 05-08-2008
Publisher: Elsevier BV
Date: 12-2013
Publisher: American Geophysical Union (AGU)
Date: 05-2007
DOI: 10.1029/2006WR005583
Publisher: American Geophysical Union (AGU)
Date: 12-2006
DOI: 10.1029/2006GL027979
Publisher: American Geophysical Union (AGU)
Date: 11-1998
DOI: 10.1029/98WR01834
Publisher: American Meteorological Society
Date: 07-2004
Publisher: Wiley
Date: 11-2012
DOI: 10.2136/VZJ2011.0199
Publisher: Elsevier BV
Date: 10-2005
Publisher: American Geophysical Union (AGU)
Date: 11-2004
DOI: 10.1029/2004GL020053
Publisher: Elsevier BV
Date: 06-2000
Publisher: American Meteorological Society
Date: 2007
DOI: 10.1175/JAS3826.1
Abstract: A parameterization for surface roughness and blending height at regional scales, under neutral atmospheric stability, is studied and tested. The analysis is based on a suite of large-eddy simulations (LES) over surfaces with varying roughness height and multiple variability scales. The LES are based on the scale-dependent Lagrangian dynamic subgrid-scale model, and the surface roughnesses at the ground are imposed using the rough-wall logarithmic law. Several patterns of roughness distribution are considered, including random tiling of patches with a wide distribution of length scales. An integral length scale, based on the one-dimensional structure function of the spatially variable roughness height, is used to define the characteristic surface variability scale, which is a critical input in many regional parameterization schemes. Properties of the simulated flow are discussed with special emphasis on the turbulence properties over patches of unequal roughness. The simulations are then used to assess a generalized form of the parameterization for the blending height and the equivalent surface roughness at regional scales that has been developed earlier for regular patterns of surface roughness (regular stripes). The results are also compared with other parameterizations proposed in the literature. Good agreement is found between the simulations and the regional-scale parameterization for the surface roughness and the blending height when this parameterization is combined with the characteristic surface variability scale proposed in this paper.
Publisher: Springer Science and Business Media LLC
Date: 11-1998
DOI: 10.1038/23845
Publisher: American Geophysical Union (AGU)
Date: 07-1999
DOI: 10.1029/1999WR900094
Publisher: IEEE
Date: 04-2008
DOI: 10.1109/IPSN.2008.28
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 1993
DOI: 10.1109/36.210446
Publisher: Informa UK Limited
Date: 10-2006
Publisher: Optica Publishing Group
Date: 10-05-2004
DOI: 10.1364/AO.43.002948
Abstract: A new method based on a two-angle approach is developed to determine the lidar solution constant from scanning elastic lidar data, hence providing a relative calibration for each lidar scan. Once the solution constant is determined, the vertical profiles of atmospheric extinction can be calculated. With this calibration method a minimization technique is used that replaces the linear regression used in a known two-angle approach that requires only local atmospheric homogeneity over a restricted altitude calibration range rather than overall horizontal homogeneity. Lidar signals from at least one pair of elevation angles are used, averaged in time when the system is operated in a permanent two-angle mode, or an arbitrary number of signal pairs is used, when a two-dimensional lidar scan is being processed. The method is tested extensively with synthetic data. The calibration method is a robust tool for determining the solution constant to the lidar equation and for obtaining vertical profiles of atmospheric extinction.
Publisher: American Geophysical Union (AGU)
Date: 09-1992
DOI: 10.1029/92WR01241
Publisher: American Geophysical Union (AGU)
Date: 28-11-2021
DOI: 10.1029/2021GL095479
Abstract: Katabatic flows are notoriously difficult to model for a variety of reasons. Notably, the assumptions underpinning Monin‐Obukhov similarity theory (MOST) are inherently violated by the sloping terrain, causing the traditional flux‐gradient relations used in numerical weather prediction models to break down. Focusing on turbulent momentum transport, we show significant flux ergence, further violating MOST assumptions, and that the traditional parameterizations fail even with local scaling for katabatic flow. In response, we propose a modified local‐MOST stability‐correction function, informed by near‐surface turbulence observations collected over two mountainous slopes with inclination angles ( ) of and . The proposed relation includes directly, making data from both slopes collapse with unprecedented agreement. RMSE between measured fluxes and estimates from the proposed and Businger et al. (1971, 0.1175/1520-0469(1971)028 :FPRITA .0.CO ) relations show significant improvement. Results can be used to inform future development of wall‐model and turbulence closures in the katabatic flow layer.
Publisher: Elsevier BV
Date: 04-2015
Publisher: American Geophysical Union (AGU)
Date: 02-2007
DOI: 10.1029/2006WR005177
Publisher: American Meteorological Society
Date: 08-2007
DOI: 10.1175/JAS3989.1
Abstract: Particle image velocimetry (PIV) measurements just within and above a mature corn canopy have been performed to clarify the small-scale spatial structure of the turbulence. The smallest resolved scales are about 15 times the Kolmogorov length scale (η ≈ 0.4 mm), the Taylor microscales are about 100η, and the Taylor scale Reynolds numbers range between R λ = 2000 and 3000. The vertical profiles of mean flow and turbulence parameters match those found in previous studies. Frequency spectra, obtained using the data as time series, are combined with instantaneous spatial spectra to resolve more than five orders of magnitude of length scales. They display an inertial range spanning three decades. However, the small-scale turbulence in the dissipation range exhibits anisotropy at all measurement heights, in spite of apparent agreement with conditions for reaching local isotropy, following a high-Reynolds-number wind tunnel study. Directly calculated subgrid-scale (SGS) energy flux, determined by spatially filtering the PIV data, increases significantly with decreasing filter size, providing support for the existence of a spectral shortcut that bypasses the cascading process and injects energy directly into small scales. The highest measured SGS flux is about 40% of the estimated energy cascading rate as determined from a −5/3 fit to the spectra. Terms appearing in the turbulent kinetic energy budget that can be calculated from the PIV data are in agreement with previous results. Evidence of a very strong correlation between dissipation rate and out-of-plane component of the vorticity is demonstrated by a striking similarity between their time series.
Publisher: Elsevier BV
Date: 08-2002
Publisher: American Geophysical Union (AGU)
Date: 05-2012
DOI: 10.1029/2012WR012061
Publisher: American Geophysical Union (AGU)
Date: 2013
DOI: 10.1029/2012WR012181
Publisher: American Meteorological Society
Date: 08-1994
Publisher: American Geophysical Union (AGU)
Date: 06-2009
DOI: 10.1029/2008WR007544
Publisher: Springer Science and Business Media LLC
Date: 10-02-2012
Publisher: Springer Science and Business Media LLC
Date: 09-1998
Publisher: American Geophysical Union (AGU)
Date: 28-06-2013
DOI: 10.1002/GRL.50642
Publisher: American Geophysical Union (AGU)
Date: 06-1996
DOI: 10.1029/96WR00287
Publisher: Springer Science and Business Media LLC
Date: 05-07-2008
Publisher: American Geophysical Union (AGU)
Date: 10-2013
DOI: 10.1002/2013EO400012
Publisher: Elsevier BV
Date: 08-2000
Publisher: Cambridge University Press (CUP)
Date: 10-11-0003
DOI: 10.1017/S0022112010004015
Abstract: A field experiment – the Snow Horizontal Array Turbulence Study (SnoHATS) – has been performed over an extensive glacier in Switzerland in order to study small-scale turbulence in the stable atmospheric surface layer, and to investigate the role, dynamics and modelling of the subgrid scales (SGSs) in the context of large-eddy simulations. The a priori data analysis aims at comparing the role and behaviour of the SGSs under stable conditions with previous studies under neutral or unstable conditions. It is found that the SGSs in a stable surface layer remain an important sink of temperature variance and turbulent kinetic energy from the resolved scales and carry a significant portion of the fluxes when the filter scale is larger than the distance to the wall. The fraction of SGS fluxes (out of the total fluxes) is found to be independent of stability. In addition, the stress–strain alignment is similar to the alignment under neutral and unstable conditions. The model coefficients vary considerably with stability but in a manner consistent with previous findings, which also showed that scale-dependent dynamic models can capture this variation. Furthermore, the variation of the coefficients for both momentum and heat SGS fluxes can be shown to be better explained by stability parameters based on vertical gradients, rather than vertical fluxes. These findings suggest that small-scale turbulence dynamics and SGS modelling under stable conditions share many important properties with neutral and convective conditions, and that a unified approach is thus possible. This paper concludes with a discussion of some other challenges for stable boundary-layer simulations that are not encountered in the neutral or unstable cases.
Publisher: Springer Science and Business Media LLC
Date: 23-07-0004
Publisher: American Meteorological Society
Date: 31-10-2013
Abstract: A new wall shear stress model to be used as a wall boundary condition for large-eddy simulations of the atmospheric boundary layer is proposed. The new model computes the wall shear stress and the vertical derivatives of the streamwise velocity component by means of a modified, instantaneous, and local law-of-the-wall formulation. By formulating a correction for the modeled shear stress, using experimental findings of a logarithmic region in the streamwise turbulent fluctuations, the need for a filter is eliminated. This allows one to model the wall shear stress locally, and at the same time accurately recover the correct average value. The proposed model has been applied to both unique high Reynolds number experimental data and a suite of large-eddy simulations, and compared to previous models. It is shown that the proposed model performs equally well or better than the previous filtered models. A nonfiltered model, such as the one proposed, is an essential first step in developing a universal wall shear stress model that can be used for flow over heterogeneous surfaces, studies of diurnal cycles, or analyses of flow over complex terrain.
Publisher: Springer Science and Business Media LLC
Date: 2003
Publisher: American Geophysical Union (AGU)
Date: 07-1993
DOI: 10.1029/93WR00569
Publisher: American Geophysical Union (AGU)
Date: 05-2013
DOI: 10.1002/WRCR.20227
Publisher: Elsevier BV
Date: 03-2008
Publisher: American Society of Civil Engineers (ASCE)
Date: 12-2015
Publisher: Springer Science and Business Media LLC
Date: 2005
Publisher: American Geophysical Union (AGU)
Date: 12-2006
DOI: 10.1029/2006WR005326
Publisher: IOP Publishing
Date: 10-1995
Publisher: American Meteorological Society
Date: 2005
Publisher: Association for Computing Machinery (ACM)
Date: 02-2010
Abstract: SensorScope is a turnkey solution for environmental monitoring systems, based on a wireless sensor network and resulting from a collaboration between environmental and network researchers. Given the interest in climate change, environmental monitoring is a domain where sensor networks will have great impact by providing high resolution spatio-temporal data for long periods of time. SensorScope is such a system, which has already been successfully deployed multiple times in various environments (e.g., mountainous, urban). Here, we describe the overall hardware and software architectures and especially focus on the sensor network itself. We also describe one of our most prominent deployments, on top of a rock glacier in Switzerland, which resulted in the description of a micro-climate phenomenon leading to cold air release from a rock-covered glacier in a region of high alpine risks. Another focus of this paper is the description of what happened behind the scenes to turn SensorScope from a laboratory experiment into successful outdoor deployments in harsh environments. Illustrated by various ex les, we point out many lessons learned while working on the project. We indicate the importance of simple code, well suited to the application, as well as the value of close interaction with end-users in planning and running the network and finally exploiting the data.
Publisher: AIP Publishing
Date: 19-01-2005
DOI: 10.1063/1.1839152
Abstract: A scale-dependent dynamic subgrid model based on Lagrangian time averaging is proposed and tested in large eddy simulations (LES) of high-Reynolds number boundary layer flows over homogeneous and heterogeneous rough surfaces. The model is based on the Lagrangian dynamic Smagorinsky model in which required averages are accumulated in time, following fluid trajectories of the resolved velocity field. The model allows for scale dependence of the coefficient by including a second test-filtering operation to determine how the coefficient changes as a function of scale. The model also uses the empirical observation that when scale dependence occurs (such as when the filter scale approaches the limits of the inertial range), the classic dynamic model yields the coefficient value appropriate for the test-filter scale. Validation tests in LES of high Reynolds number, rough wall, boundary layer flow are performed at various resolutions. Results are compared with other eddy-viscosity subgrid-scale models. Unlike the Smagorinsky–Lilly model with wall-d ing (which is overdissipative) or the scale-invariant dynamic model (which is underdissipative), the scale-dependent Lagrangian dynamic model is shown to have good dissipation characteristics. The model is also tested against detailed atmospheric boundary layer data that include measurements of the response of the flow to abrupt transitions in wall roughness. For such flows over variable surfaces, the plane-averaged version of the dynamic model is not appropriate and the Lagrangian averaging is desirable. The simulated wall stress overshoot and relaxation after a jump in surface roughness and the velocity profiles at several downstream distances from the jump are compared to the experimental data. Results show that the dynamic Smagorinsky coefficient close to the wall is very sensitive to the underlying local surface roughness, thus justifying the use of the Lagrangian formulation. In addition, the Lagrangian formulation reproduces experimental data more accurately than the planar-averaged formulation in simulations over heterogeneous rough walls.
Publisher: American Meteorological Society
Date: 06-2007
DOI: 10.1175/JAS3930.1
Abstract: Phenomena such as large-scale shear, buoyancy, and the proximity to the ground surface significantly affect interactions among scales in atmospheric boundary layer turbulent flows. Hence, these phenomena impact parameters that enter subgrid-scale (SGS) parameterizations used in large eddy simulations (LES) of the atmospheric boundary layer. The effects of these phenomena upon SGS parameters have, to date, been studied mostly as functions of the global state of the flow. For instance, the Smagorinsky coefficient has been measured as a function of the mean shear and stability condition of the atmosphere as determined from the average surface heat and momentum fluxes. However, in LES the global average field values are often difficult to determine a priori and the SGS parameters ideally must be expressed as a function of local flow variables that characterize the instantaneous flow phenomena. With the goal of improving the Smagorinsky closure, in this study several dimensionless parameters characterizing the local structure and important dynamical characteristics of the flow are defined. These local parameters include enstrophy, vortex stretching, self- lification of strain rate, and normalized temperature gradient and all are defined in such a way that they remain bounded under all circumstances. The dependence of the Smagorinsky coefficient on these local parameters is studied a priori from field data measured in the atmospheric surface layer and, as a reference point, from direct numerical simulation of neutrally buoyant, isotropic turbulence. To capture the local effects in a statistically meaningful fashion, conditional averaging is used. Results show various important and interrelated trends, such as significant increases of the coefficient in regions of large strain-rate self- lification and vortex stretching. Results also show that the joint dependence on the parameters is rather complicated and cannot be described by products of functions that depend on single parameters. Dependence on locally defined parameters is expected to improve the SGS model by sensitizing it to local flow conditions and by enabling possible generalizations of the dynamic model based on conditional averaging.
Publisher: Springer Netherlands
Date: 2010
Publisher: American Chemical Society (ACS)
Date: 18-03-2006
DOI: 10.1021/ES051708M
Abstract: Modeling air pollutant transport and dispersion in urban environments is especially challenging due to complex ground topography. In this study, we describe a large eddy simulation (LES) tool including a new dynamic subgrid closure and boundary treatment to model urban dispersion problems. The numerical model is developed, validated, and extended to a realistic urban layout. In such applications fairly coarse grids must be used in which each building can be represented using relatively few grid-points only. By carrying out LES of flow around a square cylinder and of flow over surface-mounted cubes, the coarsest resolution required to resolve the bluff body's cross section while still producing meaningful results is established. Specifically, we perform grid refinement studies showing that at least 6-8 grid points across the bluff body are required for reasonable results. The performance of several subgrid models is also compared. Although effects of the subgrid models on the mean flow are found to be small, dynamic Lagrangian models give a physically more realistic subgrid-scale (SGS) viscosity field. When scale-dependence is taken into consideration, these models lead to more realistic resolved fluctuating velocities and spectra. These results set the minimum grid resolution and subgrid model requirements needed to apply LES in simulations of neutral atmospheric boundary layer flow and scalar transport over a realistic urban geometry. The results also illustrate the advantages of LES over traditional modeling approaches, particularly its ability to take into account the complex boundary details and the unsteady nature of atmospheric boundary layer flow. Thus LES can be used to evaluate probabilities of extreme events (such as probabilities of exceeding threshold pollutant concentrations). Some comments about computer resources required for LES are also included.
Publisher: Springer Science and Business Media LLC
Date: 1994
DOI: 10.1007/BF00613584
Publisher: American Geophysical Union (AGU)
Date: 04-1993
DOI: 10.1029/92WR02593
Publisher: Springer Science and Business Media LLC
Date: 1994
DOI: 10.1007/BF00613585
Publisher: Copernicus GmbH
Date: 06-08-2015
DOI: 10.5194/HESS-17-3171-2013
Abstract: Abstract. When inferring models from hydrological data or calibrating hydrological models, we are interested in the information content of those data to quantify how much can potentially be learned from them. In this work we take a perspective from (algorithmic) information theory, (A)IT, to discuss some underlying issues regarding this question. In the information-theoretical framework, there is a strong link between information content and data compression. We exploit this by using data compression performance as a time series analysis tool and highlight the analogy to information content, prediction and learning (understanding is compression). The analysis is performed on time series of a set of catchments. We discuss both the deeper foundation from algorithmic information theory, some practical results and the inherent difficulties in answering the following question: "How much information is contained in this data set?". The conclusion is that the answer to this question can only be given once the following counter-questions have been answered: (1) information about which unknown quantities? and (2) what is your current state of knowledge/beliefs about those quantities? Quantifying information content of hydrological data is closely linked to the question of separating aleatoric and epistemic uncertainty and quantifying maximum possible model performance, as addressed in the current hydrological literature. The AIT perspective teaches us that it is impossible to answer this question objectively without specifying prior beliefs.
Publisher: Springer Science and Business Media LLC
Date: 22-02-2013
Publisher: Wiley
Date: 03-07-2012
DOI: 10.1002/QJ.1985
Publisher: American Chemical Society (ACS)
Date: 04-02-2010
DOI: 10.1021/ES902654F
Abstract: Elevated in-stream temperature has led to a surge in the occurrence of parasitic intrusion proliferative kidney disease and has resulted in fish kills throughout Switzerland's waterways. Data from distributed temperature sensing (DTS) in-stream measurements for three cloud-free days in August 2007 over a 1260 m stretch of the Boiron de Merges River in southwest Switzerland were used to calibrate and validate a physically based one-dimensional stream temperature model. Stream temperature response to three distinct riparian conditions were then modeled: open, in-stream reeds, and forest cover. Simulation predicted a mean peak stream temperature increase of 0.7 °C if current vegetation was removed, an increase of 0.1 °C if dense reeds covered the entire stream reach, and a decrease of 1.2 °C if a mature riparian forest covered the entire reach. Understanding that full vegetation canopy cover is the optimal riparian management option for limiting stream temperature, in-stream reeds, which require no riparian set-aside and grow very quickly, appear to provide substantial thermal control, potentially useful for land-use management.
Publisher: American Geophysical Union (AGU)
Date: 09-1992
DOI: 10.1029/92WR01149
Publisher: Elsevier BV
Date: 2008
Publisher: American Meteorological Society
Date: 12-2007
Abstract: An improved measurement methodology and a data-processing technique for multiangle data obtained with an elastic scanning lidar in clear atmospheres are introduced. Azimuthal and slope scans are combined to reduce the atmospheric heterogeneity. Vertical profiles of optical depth and intercept (proportional to the logarithm of the backscatter coefficient) are determined. The purpose of this approach is to identify and remove data points that distort the regression analysis results in order to improve the accuracy of the retrieved optical depth and of the intercept. In addition, the influence of systematic distortions has been investigated. Furthermore, profiles of the optical depth, intercept, and the range-squared-corrected signals have been used to determine the lidar overlap function as a function of range. Simulation and experimental results of this data-processing technique are presented.
Publisher: Copernicus GmbH
Date: 22-05-2013
Abstract: Abstract. A new Raman lidar for unattended, round-the-clock measurement of vertical water vapor profiles for operational use by the MeteoSwiss has been developed during the past years by the Swiss Federal Institute of Technology, Lausanne. The lidar uses narrow field-of-view, narrowband configuration, a UV laser, and four 30 cm in diameter mirrors, fiber-coupled to a grating polychromator. The optical design allows water vapor retrieval from the incomplete overlap region without instrument-specific range-dependent corrections. The daytime vertical range covers the mid-troposphere, whereas the nighttime range extends to the tropopause. The near range coverage is extended down to 100 m AGL by the use of an additional fiber in one of the telescopes. This paper describes the system layout and technical realization. Day- and nighttime lidar profiles compared to Vaisala RS92 and Snow White® profiles and a six-day continuous observation are presented as an illustration of the lidar measurement capability.
Publisher: American Geophysical Union (AGU)
Date: 04-1995
DOI: 10.1029/94WR01949
Publisher: American Geophysical Union (AGU)
Date: 10-2011
DOI: 10.1029/2011WR010730
Publisher: Elsevier BV
Date: 08-2010
Publisher: Elsevier BV
Date: 12-1997
Publisher: American Geophysical Union (AGU)
Date: 06-2006
DOI: 10.1029/2005WR004685
Publisher: Springer Science and Business Media LLC
Date: 11-05-2007
Publisher: American Geophysical Union (AGU)
Date: 08-2009
DOI: 10.1029/2008WR007600
Publisher: American Geophysical Union (AGU)
Date: 24-07-2019
DOI: 10.1029/2018JD029614
Publisher: American Geophysical Union (AGU)
Date: 08-2001
DOI: 10.1029/2000WR000189
Publisher: Springer Science and Business Media LLC
Date: 06-1993
DOI: 10.1007/BF00711705
Publisher: Elsevier BV
Date: 08-2000
Publisher: Springer Science and Business Media LLC
Date: 12-1995
DOI: 10.1007/BF00709237
Publisher: Springer Science and Business Media LLC
Date: 17-08-2019
Publisher: American Physical Society (APS)
Date: 05-08-1985
Publisher: Elsevier BV
Date: 04-2011
Publisher: American Meteorological Society
Date: 03-2007
DOI: 10.1175/JTECH1991.1
Abstract: In field experiments designed to study subgrid-scale parameterizations for large eddy simulation, the flow field is often measured and then filtered in two-dimensional planes. This two-dimensional filtering serves as a surrogate for three-dimensional filtering. The question of whether this will yield accurate results in subgrid-scale (SGS) models is addressed by analyzing data from a field experiment in which 16 sonic anemometers were deployed in a four by four grid. The experiment was held in July 2002 at the Surface Layer Turbulence and Environmental Science Test (SLTEST) facility in the Utah West Desert. The full SGS stress tensor and its parameterizations using both two- and three-dimensional filterings are obtained. Comparisons are given between two- and three-dimensional filterings of the field measurements based on probability density functions (PDFs) and energy spectra of the SGS stress elements. The PDFs reveal that quantities calculated with two-dimensional filtering exhibit greater intermittency than those computed with three-dimensional filtering at the same scale. From the spectra it is observed that the different filtering methods result in similar behavior, but that spectra of SGS stress components computed with a three-dimensional filter roll off at a slightly lower wavenumber than those computed with a two-dimensional filter. The PDFs and spectra of the stresses calculated with two- and three-dimensional filters can be made to collapse by reducing the three-dimensional filter scale according to Δ3−D = 0.84Δ2−D. Geometric alignment analyses are performed for the SGS heat flux, SGS stress, and filtered strain rate for the cases of stable, near-neutral, and unstable atmospheric stabilities. Under unstable and near-neutral atmospheric stability, two-dimensional filtering yields acceptable results however, under stable atmospheric stability, a new approach is recommended and delineated.
Publisher: American Geophysical Union (AGU)
Date: 07-2013
DOI: 10.1002/WRCR.20293
Publisher: Springer Science and Business Media LLC
Date: 05-2001
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 1998
DOI: 10.1109/36.718838
Publisher: Springer Science and Business Media LLC
Date: 06-08-2011
Publisher: Springer Science and Business Media LLC
Date: 07-1989
DOI: 10.1007/BF00121783
Publisher: AIP Publishing
Date: 12-2011
DOI: 10.1063/1.3663376
Abstract: Wind harvesting is fast becoming an important alternative source of energy. As wind farms become larger, they begin to attain scales at which two-way interactions with the atmospheric boundary layer (ABL) must be taken into account. Several studies have shown that there is a quantifiable effect of wind farms on the local meteorology, mainly through changes in the land-atmosphere fluxes of heat and moisture. In particular, the observed trends suggest that wind farms increase fluxes at the surface and this could be due to increased turbulence in the wakes. Conversely, simulations and laboratory experiments show that underneath wind farms, the friction velocity is decreased due to extraction of momentum by the wind turbines, a factor that could decrease scalar fluxes at the surface. In order to study this issue in more detail, a suite of large eddy simulations of an infinite (fully developed) wind turbine array boundary layer, including scalar transport from the ground surface without stratification, is performed. Results show an overall increase in the scalar fluxes of about 10%–15% when wind turbines are present in the ABL, and that the increase does not strongly depend upon wind farm loading as described by the turbines’ thrust coefficient and the wind turbines spacings. A single-column analysis including scalar transport shows that the presence of wind farms can be expected to increase slightly the scalar transport from the bottom surface and that this slight increase is due to a delicate balance between two strong opposing trends.
Publisher: AIP Publishing
Date: 12-2013
DOI: 10.1063/1.4834436
Abstract: Here we present unique evidence of a k−1 scaling behaviour in the atmospheric boundary layer and its connection to large scale coherent structures within the boundary layer. Wind lidar measurements were conducted above a lake under cold atmospheric conditions. The large coherent structures could be visually observed over Lake Geneva in Switzerland when cold air met the relatively warm water. Proper orthogonal decomposition of the experimental data acquired with the wind lidar clearly reveals coherent oscillations of both the fluctuating velocity field and the water aerosol field over the surface of the lake. Precise identification of the large coherent structures propagating in the flow allows for detailed analysis of their contribution to the total spectral budget. Additionally, it is shown that the experimental data agree well with recent theoretical predictions.
Publisher: Walter de Gruyter GmbH
Date: 03-2017
DOI: 10.1515/PIKO.2007.20
Publisher: American Geophysical Union (AGU)
Date: 08-1987
Publisher: American Geophysical Union (AGU)
Date: 1996
DOI: 10.1029/95WR02920
Publisher: Elsevier BV
Date: 03-1992
Publisher: Wiley
Date: 09-2009
DOI: 10.3732/AJB.0800407
Abstract: Pollen dispersal is a fundamental aspect of plant reproductive biology that maintains connectivity between spatially separated populations. Pollen clumping, a characteristic feature of insect-pollinated plants, is generally assumed to be a detriment to wind pollination because clumps disperse shorter distances than do solitary pollen grains. Yet pollen clumps have been observed in dispersion studies of some widely distributed wind-pollinated species. We used Ambrosia artemisiifolia (common ragweed Asteraceae), a successful invasive angiosperm, to investigate the effect of clumping on wind dispersal of pollen under natural conditions in a large field. Results of simultaneous measurements of clump size both in pollen shedding from male flowers and airborne pollen being dispersed in the atmosphere are combined with a transport model to show that rather than being detrimental, clumps may actually be advantageous for wind pollination. Initial clumps can pollinate the parent population, while smaller clumps that arise from breakup of larger clumps can cross-pollinate distant populations.
Publisher: American Geophysical Union (AGU)
Date: 17-03-2005
DOI: 10.1029/2004JD004923
Publisher: American Meteorological Society
Date: 07-2010
Abstract: The impact of surface flux boundary conditions and geostrophic forcing on multiday evolution of flow in the atmospheric boundary layer (ABL) was assessed using large-eddy simulations (LES). The LES investigations included several combinations of surface boundary conditions (temperature and heat flux) and geostrophic forcing (constant, time varying, time and height varying). The setup was based on ABL characteristics observed during a selected period of the Cooperative Atmosphere–Surface Exchange Study—1999 (CASES-99) c aign. The LES cases driven by a constant geostrophic wind achieved the best agreement with the CASES-99 observations specifically in terms of daytime surface fluxes and daytime and nighttime profiles. However, the nighttime fluxes were significantly overestimated. The LES cases with the surface temperature boundary condition and driven by a time- and height-varying geostrophic forcing showed improved agreement with the observed nighttime fluxes, but there was less agreement with other observations (e.g., daytime profiles). In terms of the surface boundary condition, the LES cases driven by either surface temperature or heat fluxes produced similar trends in terms of the daytime profiles and comparisons with data from soundings. However, in reproducing the fluxes and nighttime profiles, the agreement was better with imposed temperature because of its ability to interact dynamically with the air temperature field. Therefore, it is concluded that surface temperature boundary condition is better suited for simulations of temporally evolving ABL flow as in the diurnal evolution of the ABL.
Publisher: Elsevier BV
Date: 1998
Publisher: American Geophysical Union
Date: 2001
DOI: 10.1029/WS003P0007
Publisher: Elsevier BV
Date: 2006
Publisher: American Geophysical Union (AGU)
Date: 15-05-1998
DOI: 10.1029/98GL01176
Publisher: Springer Science and Business Media LLC
Date: 02-2008
Publisher: Springer Berlin Heidelberg
Date: 1996
Publisher: American Society of Civil Engineers (ASCE)
Date: 07-2002
Publisher: Elsevier BV
Date: 10-1999
Publisher: American Geophysical Union (AGU)
Date: 04-1995
DOI: 10.1029/94WR02978
Publisher: American Geophysical Union (AGU)
Date: 10-1992
DOI: 10.1029/92WR01683
Publisher: Springer Netherlands
Date: 2011
Publisher: IEEE
Date: 02-2012
Publisher: Springer Science and Business Media LLC
Date: 30-03-2007
Publisher: American Geophysical Union (AGU)
Date: 09-2011
DOI: 10.1029/2010WR010298
Publisher: Springer Science and Business Media LLC
Date: 18-01-2018
Publisher: Elsevier BV
Date: 08-1988
Publisher: AIP Publishing
Date: 11-2008
DOI: 10.1063/1.2992192
Abstract: Dynamic subgrid-scale models require an a priori assumption about the variation in the model coefficients with filter scale. The standard dynamic model assumes independence of scale while the scale dependent model assumes power-law dependence. In this paper, we use field experimental data to investigate the dependence of model coefficients on filter scale for the Smagorinsky and the nonlinear models. The results indicate that the assumption of a power-law dependence, which is often used in scale dependent dynamic models, holds very well for the Smagorinsky model. For the nonlinear model, the power-law assumption seems less robust but still adequate.
Publisher: American Geophysical Union (AGU)
Date: 05-1995
DOI: 10.1029/94WR03152
Publisher: Wiley
Date: 08-2010
DOI: 10.2136/VZJ2009.0109
Publisher: Elsevier BV
Date: 07-2007
Publisher: Elsevier BV
Date: 03-2009
Publisher: MDPI AG
Date: 10-04-2013
DOI: 10.3390/E15041289
Publisher: American Geophysical Union (AGU)
Date: 1992
DOI: 10.1029/91WR02482
Publisher: American Geophysical Union (AGU)
Date: 2012
DOI: 10.1029/2011GL050247
Publisher: Springer Science and Business Media LLC
Date: 07-1995
DOI: 10.1007/BF00721045
Publisher: American Geophysical Union (AGU)
Date: 04-1999
DOI: 10.1029/1998WR900121
Publisher: Springer Science and Business Media LLC
Date: 10-2003
Start Date: 10-2020
End Date: 10-2023
Amount: $465,000.00
Funder: Australian Research Council
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