Evaluation of the Impact of Horizontal Grid Spacing in Terra Incognita on Coupled Mesoscale–Microscale Simulations Using the WRF Framework

2019 ◽  
Vol 147 (3) ◽  
pp. 1007-1027 ◽  
Author(s):  
Raj K. Rai ◽  
Larry K. Berg ◽  
Branko Kosović ◽  
Sue Ellen Haupt ◽  
Jeffrey D. Mirocha ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Wrf Model ◽  
Spectral Energy ◽  
Grid Spacing ◽  
Terra Incognita ◽  
Wide Range ◽  
Large Eddy ◽  
Microscale Simulations ◽  
The Impact ◽  
Horizontal Grid

Abstract Coupled mesoscale–microscale simulations are required to provide time-varying weather-dependent inflow and forcing for large-eddy simulations under general flow conditions. Such coupling necessarily spans a wide range of spatial scales (i.e., ~10 m to ~10 km). Herein, we use simulations that involve multiple nested domains with horizontal grid spacings in the terra incognita (i.e., km) that may affect simulated conditions in both the outer and inner domains. We examine the impact on simulated wind speed and turbulence associated with forcing provided by a terrain with grid spacing in the terra incognita. We perform a suite of simulations that use combinations of varying horizontal grid spacings and turbulence parameterization/modeling using the Weather Research and Forecasting (WRF) Model using a combination of planetary boundary layer (PBL) and large-eddy simulation subgrid-scale (LES-SGS) models. The results are analyzed in terms of spectral energy, turbulence kinetic energy, and proper orthogonal decomposition (POD) energy. The results show that the output from the microscale domain depends on the type of turbulence model (e.g., PBL or LES-SGS model) used for a given horizontal grid spacing but is independent of the horizontal grid spacing and turbulence modeling of the parent domain. Simulation using a single domain produced less POD energy in the first few modes compared to a coupled simulation (one-way nesting) for similar horizontal grid spacing, which highlights that coupled simulations are required to accurately pass the mesoscale features into the microscale domain.

scholarly journals Influences of Horizontal Grid Spacing and Microphysics on WRF Forecasts of Convective Morphology Evolution for Nocturnal MCSs in Weakly Forced Environments

2019 ◽  
Vol 34 (5) ◽  
pp. 1495-1517 ◽  
Author(s):  
Jonathan E. Thielen ◽  
William A. Gallus
Keyword(s):  
Wrf Model ◽  
Forecast Accuracy ◽  
Warm Season ◽  
Grid Spacing ◽  
Convective Systems ◽  
Model Configuration ◽  
Mesoscale Convective ◽  
Microphysical Parameterization ◽  
The Impact ◽  
Horizontal Grid

Abstract Nocturnal mesoscale convective systems (MCSs) are important phenomena because of their contributions to warm-season precipitation and association with severe hazards. Past studies have shown that their morphology remains poorly forecast in current convection-allowing models operating at 3–4-km horizontal grid spacing. A total of 10 MCS cases occurring in weakly forced environments were simulated using the Weather Research and Forecasting (WRF) Model at 3- and 1-km horizontal grid spacings to investigate the impact of increased resolution on forecasts of convective morphology and its evolution. These simulations were conducted using four microphysics schemes to account for additional sensitivities to the microphysical parameterization. The observed and corresponding simulated systems were manually classified into detailed cellular and linear modes, and the overall morphology depiction and the forecast accuracy of each model configuration were evaluated. In agreement with past studies, WRF was found to underpredict the occurrence of linear modes and overpredict cellular modes at 3-km horizontal grid spacing with all microphysics schemes tested. When grid spacing was reduced to 1 km, the proportion of linear systems increased. However, the increase was insufficient to match observations throughout the evolution of the systems, and the accuracy scores showed no statistically significant improvement. This suggests that the additional linear modes may have occurred in the wrong subtypes, wrong systems, and/or at the wrong times. Accuracy scores were also shown to decrease with forecast length, with the primary decrease in score generally occurring during upscale growth in the early nocturnal period.

scholarly journals Evaluation of Lagrangian Particle Dispersion Models with Measurements from Controlled Tracer Releases

2013 ◽  
Vol 52 (12) ◽  
pp. 2623-2637 ◽  
Author(s):  
Jennifer Hegarty ◽  
Roland R. Draxler ◽  
Ariel F. Stein ◽  
Jerome Brioude ◽  
Marikate Mountain ◽  
...  
Keyword(s):  
Wrf Model ◽  
Particle Dispersion ◽  
Tracer Experiment ◽  
Grid Spacing ◽  
Dispersion Models ◽  
Lagrangian Particle ◽  
Statistical Parameters ◽  
The North ◽  
The Impact ◽  
Horizontal Grid

AbstractThree widely used Lagrangian particle dispersion models (LPDMs)—the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT), Stochastic Time-Inverted Lagrangian Transport (STILT), and Flexible Particle (FLEXPART) models—are evaluated with measurements from the controlled tracer-release experiments Cross-Appalachian Tracer Experiment (CAPTEX) and Across North America Tracer Experiment (ANATEX). The LPDMs are run forward in time driven by identical meteorological inputs from the North American Regional Reanalysis (NARR) and several configurations of the Weather Research and Forecasting (WRF) model, and the simulations of tracer concentrations are evaluated against the measurements with a ranking procedure derived from the combination of four statistical parameters. The statistical evaluation reveals that all three LPDMs have comparable skill in simulating the tracer plumes when driven by the same meteorological inputs, indicating that the differences in their formulations play a secondary role. Simulations with HYSPLIT and STILT demonstrate the benefit of using customized hourly WRF fields with 10-km horizontal grid spacing over the use of 3-hourly NARR fields with 32-km horizontal grid spacing. All three LPDMs perform better when the WRF wind fields in the planetary boundary layer are nudged to NARR, with FLEXPART benefitting the most. Case studies indicate that the nudging corrects an overestimate in plume transport speed possibly caused by a positive bias in WRF wind speeds near the surface. All three LPDMs also benefit from the use of time-averaged velocity and convective mass flux fields generated by WRF, but the impact on HYSPLIT and STILT is much greater than on FLEXPART. STILT backward runs perform as well as their forward counterparts, demonstrating this model’s reversibility and its suitability for application to inverse flux estimates.

scholarly journals Fine-Scale Structures in the Mid-Level Eyewall of Super Typhoon Rammasun (2014) Simulated With the WRF-LES Framework

2022 ◽  
Vol 9 ◽  
Author(s):  
Zhen Gao ◽  
Liguang Wu ◽  
Xingyang Zhou
Keyword(s):  
Tropical Cyclone ◽  
Three Dimensional ◽  
Wrf Model ◽  
Rapid Intensification ◽  
Grid Spacing ◽  
Super Typhoon ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Vertical Grid ◽  
Horizontal Grid

It has been numerically demonstrated that the turbulence above the boundary is important to tropical cyclone intensification and rapid intensification, but the three-dimensional structures of the sub-grid-scale (SGS) eddy have not been revealed due to the lack of observational data. In this study, two numerical simulations of Super Typhoon Rammasun (2014) were conducted with the Advanced Weather Research and Forecast (WRF) model by incorporating the large-eddy simulation (LES) technique, in which the enhanced eyewall convection and the process of rapid intensification are captured. Consistent with previous observational studies, the strong turbulent kinetic energy (TKE) is found throughout the whole eyewall inside of the radius of maximum wind in both experiments. The simulations indicate that the strong TKE is associated with horizontal rolls with the horizontal extent of 2–4 km, which are aligned azimuthally in the intense eyewall convection. It is indicated that the three-dimensional structures of the SGS eddy can be simulated with the vertical grid spacing of ∼100 m when the horizontal grid spacing is 74 m. It is suggested that there is considerable turbulence associated with azimuthally-aligned horizontal rolls in the mid-level eyewall of tropical cyclone.

scholarly journals On Bridging A Modeling Scale Gap: Mesoscale to Microscale Coupling for Wind Energy

2019 ◽  
Vol 100 (12) ◽  
pp. 2533-2550 ◽  
Author(s):  
Sue Ellen Haupt ◽  
Branko Kosovic ◽  
William Shaw ◽  
Larry K. Berg ◽  
Matthew Churchfield ◽  
...  
Keyword(s):  
Wind Energy ◽  
Department Of Energy ◽  
Physical Models ◽  
Plant Performance ◽  
Coupled Modeling ◽  
Terra Incognita ◽  
Modeling Techniques ◽  
Microscale Simulations ◽  
The Impact ◽  
Nonstationary Conditions

Abstract Accurately representing flow across the mesoscale to the microscale is a persistent roadblock for completing realistic microscale simulations. The science challenges that must be addressed to coupling at these scales include the following: 1) What is necessary to capture the variability of the mesoscale flow, and how do we avoid generating spurious rolls within the terra incognita between the scales? 2) Which methods effectively couple the mesoscale to the microscale and capture the correct nonstationary features at the microscale? 3) What are the best methods to initialize turbulence at the microscale? 4) What is the best way to handle the surface-layer parameterizations consistently at the mesoscale and the microscale? 5) How do we assess the impact of improvements in each of these aspects and quantify the uncertainty in the simulations? The U.S. Department of Energy Mesoscale-to-Microscale-Coupling project seeks to develop, verify, and validate physical models and modeling techniques that bridge the most important atmospheric scales determining wind plant performance and reliability, which impacts many meteorological applications. The approach begins with choosing case days that are interesting for wind energy for which there are observational data for validation. The team has focused on modeling nonstationary conditions for both flat and complex terrain. This paper describes the approaches taken to answer the science challenges, culminating in recommendations for best approaches for coupled modeling.

The Impact of Horizontal Grid Spacing on the Microphysical and Kinematic Structures of Strong Tropical Cyclones Simulated with the WRF-ARW Model

2009 ◽  
Vol 137 (11) ◽  
pp. 3717-3743 ◽  
Author(s):  
Alexandre O. Fierro ◽  
Robert F. Rogers ◽  
Frank D. Marks ◽  
David S. Nolan
Keyword(s):  
Mass Flux ◽  
High Surface ◽  
Surface Fluxes ◽  
Small Range ◽  
Grid Spacing ◽  
Arw Model ◽  
Parent Domain ◽  
Model Features ◽  
The Impact ◽  
Horizontal Grid

Abstract Using the Advanced Weather Research and Forecasting numerical model, the impact of horizontal grid spacing on the microphysical and kinematic structure of a numerically simulated tropical cyclone (TC), and their relationship to storm intensity was investigated with a set of five numerical simulations using input data for the case of Hurricane Rita (2005). The horizontal grid spacing of the parent domain was systematically changed such that the horizontal grid spacing of the inner nest varied from 1 to 5 km by an increment of 1 km, this while keeping geographical dimensions of the domains identical. Within this small range of horizontal grid spacing, the morphology of the simulated storms and the evolution of the kinematic and microphysics field showed noteworthy differences. As grid spacing increased, the model produced a wider, more tilted eyewall, a larger radius of maximum winds, and higher-amplitude, low wavenumber eyewall asymmetries. The coarser-resolution simulations also produced larger volume, areal coverage, and mass flux of updraft speeds ≥5 m s−1; larger volumes of condensate and ice-phase particles aloft; larger boundary layer kinetic energy; and a stronger secondary circulation. While the contribution of updrafts ≥5 m s−1 to the total updraft mass flux varied little between the five cases, the contribution of downdrafts ≤−2 m s−1 to the total downdraft mass flux was by far the largest in the finest-resolution simulation. Despite these structural differences, all of the simulations produced storms of similar intensity, as measured by peak 10-m wind speed and minimum surface pressure, suggesting that features in the higher-resolution simulations that tend to weaken TCs (i.e., smaller area of high surface fluxes and weaker total updraft mass flux) compensate for features that favor TC intensity (i.e., smaller-amplitude eyewall asymmetries and larger radial gradients). This raises the possibility that resolution increases in this range may not be as important as other model features (e.g., physical parameterization and initial condition improvements) for improving TC intensity forecasts.

High-resolution atmospheric boundary layer simulations using WRF-LES

2020 ◽  
Author(s):  
Gokhan Kirkil
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Cross Sections ◽  
Wrf Model ◽  
Field Measurements ◽  
Mean Flow ◽  
Spatial And Temporal Scales ◽  
Eddy Simulation ◽  
Wide Range ◽  
Large Eddy

<p>WRF model provides a potentially powerful framework for coupled simulations of flow covering a wide range of<br>spatial and temporal scales via a successive grid nesting capability. Nesting can be repeated down to turbulence<br>solving large eddy simulation (LES) scales, providing a means for significant improvements of simulation of<br>turbulent atmospheric boundary layers. We will present the recent progress on our WRF-LES simulations of<br>the Perdigao Experiment performed over mountainous terrain. We performed multi-scale simulations using<br>WRF’s different Planetary Boundary Layer (PBL) parameterizations as well as Large Eddy Simulation (LES)<br>and compared the results with the detailed field measurements. WRF-LES model improved the mean flow field<br>as well as second-order flow statistics. Mean fluctuations and turbulent kinetic energy fields from WRF-LES<br>solution are investigated in several cross-sections around the hill which shows good agreement with measurements.</p>

scholarly journals Simulation of the Summer Monsoon Rainfall over East Asia Using the NCEP GFS Cumulus Parameterization at Different Horizontal Resolutions

2014 ◽  
Vol 29 (5) ◽  
pp. 1143-1154 ◽  
Author(s):  
Kyo-Sun Sunny Lim ◽  
Song-You Hong ◽  
Jin-Ho Yoon ◽  
Jongil Han
Keyword(s):  
Summer Monsoon ◽  
Monsoon Rainfall ◽  
Asian Summer Monsoon ◽  
Monsoon Season ◽  
Wrf Model ◽  
Horizontal Resolution ◽  
Cumulus Parameterization ◽  
Grid Spacing ◽  
Simulated Precipitation ◽  
Horizontal Grid

Abstract The most recent version of the simplified Arakawa–Schubert (SAS) cumulus scheme in the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) (GFS SAS) is implemented in the Weather Research and Forecasting (WRF) Model with a modification of the triggering condition and the convective mass flux in order to make it dependent on the model’s horizontal grid spacing. The East Asian summer monsoon season of 2006 is selected in order to evaluate the performance of the modified GFS SAS scheme. In comparison to the original GFS SAS scheme, the modified GFS SAS scheme shows overall better agreement with the observations in terms of the simulated monsoon rainfall. The simulated precipitation from the original GFS SAS scheme is insensitive to the model’s horizontal grid spacing, which is counterintuitive because the portion of the resolved clouds in a grid box should increase as the model grid spacing decreases. This behavior of the original GFS SAS scheme is alleviated by the modified GFS SAS scheme. In addition, three different cumulus schemes (Grell and Freitas, Kain and Fritsch, and Betts–Miller–Janjić) are chosen to investigate the role of a horizontal resolution on the simulated monsoon rainfall. Although the forecast skill of the surface rainfall does not always improve as the spatial resolution increases, the improvement of the probability density function of the rain rate with the smaller grid spacing is robust regardless of the cumulus parameterization scheme.

scholarly journals An urban large-eddy-simulation-based dispersion model for marginal grid resolutions: CAIRDIO v1.0

2021 ◽  
Vol 14 (3) ◽  
pp. 1469-1492
Author(s):  
Michael Weger ◽  
Oswald Knoth ◽  
Bernd Heinold
Keyword(s):  
Air Pollution ◽  
Numerical Models ◽  
Dispersion Model ◽  
Urban Air Pollution ◽  
Horizontal Resolution ◽  
Diffuse Interface ◽  
Grid Spacing ◽  
Two Phase ◽  
Wide Range ◽  
Large Eddy

Abstract. The ability to achieve high spatial resolutions is an important feature for numerical models to accurately represent the large spatial variability of urban air pollution. On the one hand, the well-established mesoscale chemistry transport models have their obvious shortcomings due to the extensive use of physical parameterizations. On the other hand, obstacle-resolving computational fluid dynamics (CFD) models, although accurate, are still often too computationally intensive to be applied regularly for entire cities. The major reason for the inflated computational costs is the required horizontal resolution to meaningfully apply obstacle discretization, which is mostly based on boundary-fitted grids, e.g., the marker-and-cell method. In this paper, we present the new City-scale AIR dispersion model with DIffuse Obstacles (CAIRDIO v1.0), in which the diffuse interface method, simplified for non-moving obstacles, is incorporated into the governing equations for incompressible large-eddy simulations. While the diffuse interface method is widely used in two-phase modeling, this method has not been used in urban boundary-layer modeling so far. It allows us to consistently represent buildings over a wide range of spatial resolutions, including grid spacings equal to or larger than typical building sizes. This way, the gray zone between obstacle-resolving microscale simulations and mesoscale simulations can be addressed. Orographic effects can be included by using terrain-following coordinates. The dynamic core is compared against a standard quality-assured wind-tunnel dataset for dispersion-model evaluation. It is shown that the model successfully reproduces dispersion patterns within a complex city morphology across a wide range of spatial resolutions tested. As a result of the diffuse obstacle approach, the accuracy test is also passed at a horizontal grid spacing of 40 m. Although individual flow features within individual street canyons are not resolved at the coarse-grid spacing, the building effect on the dispersion of the air pollution plume is preserved at a larger scale. Therefore, a very promising application of the CAIRDIO model lies in the realization of computationally feasible yet accurate air-quality simulations for entire cities.

The Dispersion of Silver Iodide Particles from Ground-Based Generators over Complex Terrain. Part II: WRF Large-Eddy Simulations versus Observations

2014 ◽  
Vol 53 (6) ◽  
pp. 1342-1361 ◽  
Author(s):  
Lulin Xue ◽  
Xia Chu ◽  
Roy Rasmussen ◽  
Daniel Breed ◽  
Bruce Boe ◽  
...  
Keyword(s):  
Complex Terrain ◽  
Silver Iodide ◽  
Wrf Model ◽  
Static Stability ◽  
Particle Dispersion ◽  
Grid Spacing ◽  
Medicine Bow Mountains ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Orographic Clouds

AbstractA numerical modeling study has been conducted to explore the ability of the Weather Research and Forecasting (WRF) model-based large-eddy simulation (LES) with 100-m grid spacing to reproduce silver iodide (AgI) particle dispersion by comparing the model results with measurements made on 16 February 2011 over the Medicine Bow Mountains in Wyoming. Xue et al.'s recently developed AgI cloud-seeding parameterization was applied in this study to simulate AgI release from ground-based generators. Qualitative and quantitative comparisons between the LES results and observed AgI concentrations were conducted. Analyses of turbulent kinetic energy (TKE) features within the planetary boundary layer (PBL) and comparisons between the 100-m LES and simulations with 500-m grid spacing were performed as well. The results showed the following: 1) Despite the moist bias close to the ground and above 4 km AGL, the LES with 100-m grid spacing captured the essential environmental conditions except for a slightly more stable PBL relative to the observed soundings. 2) Wind shear is the dominant TKE production mechanism in wintertime PBL over complex terrain and generates a PBL of about 1000-m depth. The terrain-induced turbulent eddies are primarily responsible for the vertical dispersion of AgI particles. 3) The LES-simulated AgI plumes were shallow and narrow, in agreement with observations. The LES overestimated AgI concentrations close to the ground, which is consistent with the higher static stability in the model than is observed. 4) Non-LES simulations using PBL schemes had difficulty in capturing the shear-dominant turbulent PBL structure over complex terrain in wintertime. Therefore, LES of wintertime orographic clouds with grid spacing close to 500 m or finer are recommended.

scholarly journals A Case Study of Radar Observations and WRF LES Simulations of the Impact of Ground-Based Glaciogenic Seeding on Orographic Clouds and Precipitation. Part II: AgI Dispersion and Seeding Signals Simulated by WRF

2016 ◽  
Vol 55 (2) ◽  
pp. 445-464 ◽  
Author(s):  
Lulin Xue ◽  
Xia Chu ◽  
Roy Rasmussen ◽  
Daniel Breed ◽  
Bart Geerts
Keyword(s):  
Nucleation Rate ◽  
Wrf Model ◽  
Grid Spacing ◽  
Medicine Bow Mountains ◽  
Eddy Simulation ◽  
Cloud Dynamics ◽  
Vertical Dispersion ◽  
Orographic Clouds ◽  
Glaciogenic Seeding ◽  
The Impact

AbstractSeveral Weather Research and Forecasting (WRF) Model simulations of natural and seeded clouds have been conducted in non-LES and LES (large-eddy simulation) modes to investigate the seeding impact on wintertime orographic clouds for an actual seeding case on 18 February 2009 in the Medicine Bow Mountains of Wyoming. Part I of this two-part series has shown the capability of WRF LES with 100-m grid spacing to capture the essential environmental conditions by comparing the model results with measurements from a variety of instruments. In this paper, the silver iodide (AgI) dispersion features, the AgI impacts on the turbulent kinetic energy (TKE), the microphysics, and the precipitation are examined in detail using the model data, which leads to five main results. 1) The vertical dispersion of AgI particles is more efficient in cloudy conditions than in clear conditions. 2) The wind shear and the buoyancy are both important TKE production mechanisms in the wintertime PBL over complex terrain in cloudy conditions. The buoyancy-induced eddies are more responsible for the AgI vertical dispersion than the shear-induced eddies are. 3) Seeding has insignificant effects on the cloud dynamics. 4) AgI particles released from the ground-based generators affect the cloud within the boundary layer below 1 km AGL through nucleating extra ice crystals, converting liquid water into ice, depleting more vapor, and generating more precipitation on the ground. The AgI nucleation rate is inversely related to the natural ice nucleation rate. 5) The seeding effects on the ground precipitation are confined within narrow areas. The relative seeding effect ranges between 5% and 20% for the simulations with different grid spacing.

Sign in / Sign up

Export Citation Format

Share Document