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 Uncertainty in Lagrangian pollutant transport simulations due to meteorological uncertainty from a mesoscale WRF ensemble

2014 ◽  
Vol 7 (6) ◽  
pp. 2817-2829 ◽  
Author(s):  
W. M. Angevine ◽  
J. Brioude ◽  
S. McKeen ◽  
J. S. Holloway
Keyword(s):  
Wrf Model ◽  
Particle Dispersion ◽  
Eastern North America ◽  
Dispersion Models ◽  
Mixing Height ◽  
Lagrangian Particle ◽  
Tracer Concentration ◽  
Propagation Of Uncertainty ◽  
Temporal Averaging ◽  
Tracer Age

Abstract. Lagrangian particle dispersion models require meteorological fields as input. Uncertainty in the driving meteorology is one of the major uncertainties in the results. The propagation of uncertainty through the system is not simple, and it has not been thoroughly explored. Here, we take an ensemble approach. Six different configurations of the Weather Research and Forecast (WRF) model drive otherwise identical simulations with FLEXPART-WRF for 49 days over eastern North America. The ensemble spreads of wind speed, mixing height, and tracer concentration are presented. Uncertainty of tracer concentrations due solely to meteorological uncertainty is 30–40%. Spatial and temporal averaging reduces the uncertainty marginally. Tracer age uncertainty due solely to meteorological uncertainty is 15–20%. These are lower bounds on the uncertainty, because a number of processes are not accounted for in the analysis.

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 Uncertainty in Lagrangian pollutant transport simulations due to meteorological uncertainty at mesoscale

2014 ◽  
Vol 7 (4) ◽  
pp. 4603-4643 ◽  
Author(s):  
W. M. Angevine ◽  
J. Brioude ◽  
S. McKeen ◽  
J. S. Holloway
Keyword(s):  
Wrf Model ◽  
Particle Dispersion ◽  
Eastern North America ◽  
Dispersion Models ◽  
Mixing Height ◽  
Lagrangian Particle ◽  
Tracer Concentration ◽  
Propagation Of Uncertainty ◽  
Temporal Averaging ◽  
Tracer Age

Abstract. Lagrangian particle dispersion models require meteorological fields as input. Uncertainty in the driving meteorology is one of the major uncertainties in the results. The propagation of uncertainty through the system is not simple, and has not been thoroughly explored. Here, we take an ensemble approach. Six different configurations of the Weather Research and Forecast (WRF) model drive otherwise identical simulations with FLEXPART for 49 days over eastern North America. The ensemble spreads of wind speed, mixing height, and tracer concentration are presented. Uncertainty of tracer concentrations due solely to meteorological uncertainty is 30–40%. Spatial and temporal averaging reduces the uncertainty marginally. Tracer age uncertainty due solely to meteorological uncertainty is 15–20%. These are lower bounds on the uncertainty, because a number of processes are not accounted for in the analysis.

scholarly journals Quantitative evaluation of numerical integration schemes for Lagrangian particle dispersion models

2016 ◽  
Author(s):  
Huda Mohd. Ramli ◽  
J. Gavin Esler
Keyword(s):  
Planck Equation ◽  
Particle Dispersion ◽  
Test Problems ◽  
Hermite Function ◽  
Dispersion Models ◽  
Lagrangian Particle ◽  
Integration Schemes ◽  
Fokker Planck Equation ◽  
Long Time ◽  
Fokker Planck

Abstract. A rigorous methodology for the evaluation of integration schemes for Lagrangian particle dispersion models (LPDMs) is presented. A series of one-dimensional test problems are introduced, for which the Fokker-Planck equation is solved numerically using a finite-difference discretisation in physical space, and a Hermite function expansion in velocity space. Numerical convergence errors in the Fokker-Planck equation solutions are shown to be much less than the statistical error associated with a practical-sized ensemble (N = 106) of LPDM solutions, hence the former can be used to validate the latter. The test problems are then used to evaluate commonly used LPDM integration schemes. The results allow for optimal time-step selection for each scheme, given a required level of accuracy. The following recommendations are made for use in operational models. First, if computational constraints require the use of moderate to long time steps it is more accurate to solve the random displacement model approximation to the LPDM, rather than use existing schemes designed for long time-steps. Second, useful gains in numerical accuracy can be obtained, at moderate additional computational cost, by using the relatively simple "small-noise" scheme of Honeycutt.

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.

scholarly journals Impact of optimized mixing heights on simulated regional atmospheric transport of CO<sub>2</sub>

2014 ◽  
Vol 14 (14) ◽  
pp. 7149-7172 ◽  
Author(s):  
R. Kretschmer ◽  
C. Gerbig ◽  
U. Karstens ◽  
G. Biavati ◽  
A. Vermeulen ◽  
...  
Keyword(s):  
Dispersion Model ◽  
Synthetic Data ◽  
Wrf Model ◽  
Horizontal Resolution ◽  
Particle Dispersion ◽  
Random Errors ◽  
Tracer Transport ◽  
European Continent ◽  
Co2 Transport ◽  
The Impact

Abstract. The mixing height (MH) is a crucial parameter in commonly used transport models that proportionally affects air concentrations of trace gases with sources/sinks near the ground and on diurnal scales. Past synthetic data experiments indicated the possibility to improve tracer transport by minimizing errors of simulated MHs. In this paper we evaluate a method to constrain the Lagrangian particle dispersion model STILT (Stochastic Time-Inverted Lagrangian Transport) with MH diagnosed from radiosonde profiles using a bulk Richardson method. The same method was used to obtain hourly MHs for the period September/October 2009 from the Weather Research and Forecasting (WRF) model, which covers the European continent at 10 km horizontal resolution. Kriging with external drift (KED) was applied to estimate optimized MHs from observed and modelled MHs, which were used as input for STILT to assess the impact on CO2 transport. Special care has been taken to account for uncertainty in MH retrieval in this estimation process. MHs and CO2 concentrations were compared to vertical profiles from aircraft in situ data. We put an emphasis on testing the consistency of estimated MHs to observed vertical mixing of CO2. Modelled CO2 was also compared with continuous measurements made at Cabauw and Heidelberg stations. WRF MHs were significantly biased by ~10–20% during day and ~40–60% during night. Optimized MHs reduced this bias to ~5% with additional slight improvements in random errors. The KED MHs were generally more consistent with observed CO2 mixing. The use of optimized MHs had in general a favourable impact on CO2 transport, with bias reductions of 5–45% (day) and 60–90% (night). This indicates that a large part of the found CO2 model–data mismatch was indeed due to MH errors. Other causes for CO2 mismatch are discussed. Applicability of our method is discussed in the context of CO2 inversions at regional scales.

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.

Comparisons of JU2003 observations with four diagnostic urban wind flow and Lagrangian particle dispersion models

2011 ◽  
Vol 45 (24) ◽  
pp. 4073-4081 ◽  
Author(s):  
Steven Hanna ◽  
John White ◽  
James Trolier ◽  
Rebecca Vernot ◽  
Michael Brown ◽  
...  
Keyword(s):  
Particle Dispersion ◽  
Wind Flow ◽  
Dispersion Models ◽  
Lagrangian Particle

scholarly journals Europe's offshore winds assessed with synthetic aperture radar, ASCAT and WRF

2020 ◽  
Vol 5 (1) ◽  
pp. 375-390 ◽  
Author(s):  
Charlotte B. Hasager ◽  
Andrea N. Hahmann ◽  
Tobias Ahsbahs ◽  
Ioanna Karagali ◽  
Tija Sile ◽  
...  
Keyword(s):  
Synthetic Aperture Radar ◽  
Wrf Model ◽  
Offshore Wind ◽  
Synthetic Aperture ◽  
Grid Spacing ◽  
North West ◽  
Wind Retrieval ◽  
The North ◽  
Ocean Wind ◽  
Aperture Radar

Abstract. Europe's offshore wind resource mapping is part of the New European Wind Atlas (NEWA) international consortium effort. This study presents the results of analysis of synthetic aperture radar (SAR) ocean wind maps based on Envisat and Sentinel-1 with a brief description of the wind retrieval process and Advanced Scatterometer (ASCAT) ocean wind maps. The wind statistics at 10 and 100 m above mean sea level (a.m.s.l.) height using an extrapolation procedure involving simulated long-term stability over oceans are presented for both SAR and ASCAT. Furthermore, the Weather Research and Forecasting (WRF) offshore wind atlas of NEWA is presented. This has 3 km grid spacing with data every 30 min for 30 years from 1989 to 2018, while ASCAT has 12.5 km and SAR has 2 km grid spacing. Offshore mean wind speed maps at 100 m a.m.s.l. height from ASCAT, SAR, WRF and ERA5 at a European scale are compared. A case study on offshore winds near Crete compares SAR and WRF for flow from the north, west and all directions. The paper highlights the ability of the WRF model to simulate the overall European wind climatology and the near-coastal winds constrained by the resolution of the coastal topography in the WRF model simulations.

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