Insights to WRF-Chem sensitivity in a zone of complex terrain in the tropical Andes: Effect of boundary conditions, chemical mechanisms, nesting, and domain configuration

Abstract A computationally efficient and inexpensive approach for using the capabilities of large-eddy simulations (LES) to model small-scale local weather phenomena is presented. The setup uses the LES capabilities of the Weather Research and Forecasting Model (WRF-LES) on a single domain that is directly driven by reanalysis data as boundary conditions. The simulated area is an example for complex terrain, and the employed parameterizations are chosen in a way to represent realistic conditions during two 48-h periods while still keeping the required computing time around 105 CPU hours. We show by evaluating turbulence characteristics that the model results conform to results from typical LES. A comparison with ground-based remote sensing data from a triple Doppler-lidar setup, employed during the “ScaleX” campaigns, shows the grade of adherence of the results to the measured local weather conditions. The representation of mesoscale phenomena, including nocturnal low-level jets, strongly depends on the temporal and spatial resolution of the meteorological boundary conditions used to drive the model. Small-scale meteorological features that are induced by the terrain, such as katabatic flows, are present in the simulated output as well as in the measured data. This result shows that the four-dimensional output of WRF-LES simulations for a real area and real episode can be technically realized, allowing a more comprehensive and detailed view of the micrometeorological conditions than can be achieved with measurements alone.

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Implementation Issues in 3D Wind Flow Predictions Over Complex Terrain

Journal of Solar Energy Engineering ◽

10.1115/1.2346702 ◽

2006 ◽

Vol 128 (4) ◽

pp. 539-553 ◽

Cited By ~ 23

Author(s):

John Prospathopoulos ◽

Spyros G. Voutsinas

Keyword(s):

Wind Energy ◽

Boundary Conditions ◽

Complex Terrain ◽

Flow Direction ◽

Region Of Interest ◽

Field Measurements ◽

Navier Stokes ◽

Wind Flow ◽

Computational Domain

Practical aspects concerning the use of 3D Navier-Stokes solvers as prediction tools for micro-siting of wind energy installations are considered. Micro-siting is an important issue for a successful application of wind energy in sites of complex terrain. There is a constantly increasing interest in using mean wind flow predictions based on Reynolds averaged Navier-Stokes (RANS) solvers in order to minimize the number of required field measurements. In this connection, certain numerical aspects, such as the extent of the numerical flow domain, the choice of the appropriate inflow boundary conditions, and the grid resolution, can decisively affect the quality of the predictions. In the present paper, these aspects are analyzed with reference to the Askervein hill data base of full scale measurements. The objective of the work is to provide guidelines with respect to the definition of appropriate boundary conditions and the construction of an adequate and effective computational grid when a RANS solver is implemented. In particular, it is concluded that (a) the ground roughness affects the predictions significantly, (b) the computational domain should have an extent permitting the full development of the flow before entering the region of interest, and (c) the quality of the predictions at the local altitude maxima depends on the grid density in the main flow direction.

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Sensitivity Analysis of the WRF Model: Wind-Resource Assessment for Complex Terrain

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-17-0121.1 ◽

2018 ◽

Vol 57 (3) ◽

pp. 733-753 ◽

Cited By ~ 23

Author(s):

Sergio Fernández-González ◽

María Luisa Martín ◽

Eduardo García-Ortega ◽

Andrés Merino ◽

Jesús Lorenzana ◽

...

Keyword(s):

Sensitivity Analysis ◽

Wind Speed ◽

Boundary Conditions ◽

Complex Terrain ◽

Wrf Model ◽

Wind Farms ◽

Ensemble Prediction ◽

Mountain Range ◽

Ensemble Prediction System ◽

Initial And Boundary Conditions

AbstractWind energy requires accurate forecasts for adequate integration into the electric grid system. In addition, global atmospheric models are not able to simulate local winds in complex terrain, where wind farms are sometimes placed. For this reason, the use of mesoscale models is vital for estimating wind speed at wind turbine hub height. In this regard, the Weather Research and Forecasting (WRF) Model allows a user to apply different initial and boundary conditions as well as physical parameterizations. In this research, a sensitivity analysis of several physical schemes and initial and boundary conditions was performed for the Alaiz mountain range in the northern Iberian Peninsula, where several wind farms are located. Model performance was evaluated under various atmospheric stabilities and wind speeds. For validation purposes, a mast with anemometers installed at 40, 78, 90, and 118 m above ground level was used. The results indicate that performance of the Global Forecast System analysis and European Centre for Medium-Range Weather Forecasts interim reanalysis (ERA-Interim) as initial and boundary conditions was similar, although each performed better under certain meteorological conditions. With regard to physical schemes, there is no single combination of parameterizations that performs best during all weather conditions. Nevertheless, some combinations have been identified as inefficient, and therefore their use is discouraged. As a result, the validation of an ensemble prediction system composed of the best 12 deterministic simulations shows the most accurate results, obtaining relative errors in wind speed forecasts that are <15%.

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Analysis of an observer strategy for initial state reconstruction of wave-like systems in unbounded domains

ESAIM Control Optimisation and Calculus of Variations ◽

10.1051/cocv/2019026 ◽

2020 ◽

Vol 26 ◽

pp. 45

Author(s):

S. Imperiale ◽

P. Moireau ◽

A. Tonnoir

Keyword(s):

Boundary Conditions ◽

Time Reversal ◽

Unbounded Domains ◽

Reconstruction Algorithm ◽

Initial Condition ◽

Transparent Boundary Conditions ◽

Initial State ◽

Domain Configuration ◽

Robustness To Noise ◽

Consistency Error

We are interested in reconstructing the initial condition of a wave equation in an unbounded domain configuration from measurements available in time on a subdomain. To solve this problem, we adopt an iterative strategy of reconstruction based on observers and time reversal adjoint formulations. We prove the convergence of our reconstruction algorithm with perfect measurements and its robustness to noise. Moreover, we develop a complete strategy to practically solve this problem on a bounded domain using artificial transparent boundary conditions to account for the exterior domain. Our work then demonstrates that the consistency error introduced by the use of approximate transparent boundary conditions is compensated by the stabilization properties obtained from the use of the available measurements, hence allowing to still be able to reconstruct the unknown initial condition.

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RANS simulation of neutral atmospheric boundary layer flows over complex terrain by proper imposition of boundary conditions and modification on the k-ε model

Environmental Fluid Mechanics ◽

10.1007/s10652-015-9408-1 ◽

2015 ◽

Vol 16 (1) ◽

pp. 1-23 ◽

Cited By ~ 26

Author(s):

B. W. Yan ◽

Q. S. Li ◽

Y. C. He ◽

P. W. Chan

Keyword(s):

Boundary Layer ◽

Boundary Conditions ◽

Atmospheric Boundary Layer ◽

Complex Terrain ◽

Boundary Layer Flows ◽

Rans Simulation

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Mesoscale to Microscale Simulations over Complex Terrain with the Immersed Boundary Method in the Weather Research and Forecasting Model

Monthly Weather Review ◽

10.1175/mwr-d-19-0071.1 ◽

2020 ◽

Vol 148 (2) ◽

pp. 577-595 ◽

Cited By ~ 2

Author(s):

David J. Wiersema ◽

Katherine A. Lundquist ◽

Fotini Katopodes Chow

Keyword(s):

Boundary Conditions ◽

Immersed Boundary Method ◽

Complex Terrain ◽

Wrf Model ◽

Weather Research And Forecasting ◽

Immersed Boundary ◽

Eddy Simulation ◽

Boundary Method ◽

Large Eddy ◽

Terrain Following

Abstract Improvements to the Weather Research and Forecasting (WRF) Model are made to enable multiscale simulations over highly complex terrain with dynamically downscaled boundary conditions from the mesoscale to the microscale. Over steep terrain, the WRF Model develops numerical errors that are due to grid deformation of the terrain-following coordinates. An alternative coordinate system, the immersed boundary method (IBM), has been implemented into WRF, allowing for simulations over highly complex terrain; however, the new coordinate system precluded nesting within mesoscale simulations using WRF’s native terrain-following coordinates. Here, the immersed boundary method and WRF’s grid-nesting framework are modified to seamlessly work together. This improved framework for the first time allows for large-eddy simulation over complex (urban) terrain with IBM to be nested within a typical mesoscale WRF simulation. Simulations of the Joint Urban 2003 field campaign in Oklahoma City, Oklahoma, are performed using a multiscale five-domain nested configuration, spanning horizontal grid resolutions from 6 km to 2 m. These are compared with microscale-only simulations with idealized lateral boundary conditions and with observations of wind speed/direction and SF6 concentrations from a controlled release from intensive observation period 3. The multiscale simulation, which is configured independent of local observations, shows similar model skill predicting wind speed/direction and improved skill predicting SF6 concentrations when compared with the idealized simulations, which require use of observations to set mean flow conditions. Use of this improved multiscale framework shows promise for enabling large-eddy simulation over highly complex terrain with dynamically downscaled boundary conditions from mesoscale models.

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Use of the Magnetostatic Analogue In Electromagnetic Lens Engineering

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100068795 ◽

1970 ◽

Vol 28 ◽

pp. 360-361

Author(s):

John W. Coleman

Keyword(s):

Boundary Conditions ◽

High Performance ◽

Force Fields ◽

Optical Design ◽

Direct Conversion ◽

Design Engineering ◽

Design Data ◽

Scalar Potentials ◽

Geometric Elements ◽

At Will

In the design engineering of high performance electromagnetic lenses, the direct conversion of electron optical design data into drawings for reliable hardware is oftentimes difficult, especially in terms of how to mount parts to each other, how to tolerance dimensions, and how to specify finishes. An answer to this is in the use of magnetostatic analytics, corresponding to boundary conditions for the optical design. With such models, the magnetostatic force on a test pole along the axis may be examined, and in this way one may obtain priority listings for holding dimensions, relieving stresses, etc..The development of magnetostatic models most easily proceeds from the derivation of scalar potentials of separate geometric elements. These potentials can then be conbined at will because of the superposition characteristic of conservative force fields.

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