Evaluation of the Ventilation Index in Complex Terrain: A Dispersion Modeling Study

AbstractIn this study, the Flexible Particle (FLEXPART)-WRF, a Lagrangian particle dispersion model, is employed to simulate pollutant dispersion in and near the Lehigh Gap, a gap in a prominent ridgeline in eastern Pennsylvania. FLEXPART-WRF is used to evaluate the diagnostic value of the ventilation index (VI), an index that describes the potential for smoke or other pollutants to ventilate away from a source, for indicating dispersion potential in complex terrain. Little is known about the effectiveness of the ventilation index in diagnosing dispersion potential in complex terrain. The modeling approach used in this study is to release a dense cloud of particles across a portion of the model domain and evaluate particle behavior and VI diagnostic value in areas of the domain with differing terrain characteristics. Although both horizontal and vertical dispersion are examined, the study focuses primarily on horizontal dispersion, assessed quantitatively by calculating horizontal residence time (HRT) within a 1-km-radius circle surrounding the particle release point. Analysis of HRT across the domain reveals horizontal dispersion patterns that are influenced by the ridgeline and the Lehigh Gap. Comparison of VI and HRT in different areas of the domain reveals a robust relationship windward of the ridgeline and a weak relationship leeward of the ridgeline and in the vicinity of the Lehigh Gap. The results of this study suggest that VI users should consider whether they are windward or leeward of topographic features, and highlight the need for an alternative metric that better takes into account the influence of the terrain on dispersion.

Download Full-text

AIRCITY: A Very High Resolution Atmospheric Dispersion Modeling System for Paris

Volume 1D, Symposia: Transport Phenomena in Mixing; Turbulent Flows; Urban Fluid Mechanics; Fluid Dynamic Behavior of Complex Particles; Analysis of Elementary Processes in Dispersed Multiphase Flows; Multiphase Flow With Heat/Mass Transfer in Process Technology; Fluid Mechanics of Aircraft and Rocket Emissions and Their Environmental Impacts; High Performance CFD Computation; Performance of Multiphase Flow Systems; Wind Energy; Uncertainty Quantification in Flow Measurements and Simulations ◽

10.1115/fedsm2014-21820 ◽

2014 ◽

Cited By ~ 2

Author(s):

J. Moussafir ◽

C. Olry ◽

M. Nibart ◽

A. Albergel ◽

P. Armand ◽

...

Keyword(s):

Air Quality ◽

Parallel Machines ◽

Road Traffic ◽

Dispersion Model ◽

Atmospheric Dispersion ◽

Parallel Architecture ◽

Pollutant Dispersion ◽

Particle Dispersion ◽

Dispersion Modeling ◽

The European Union

The AIRCITY project, partly funded by the European Union, is now successfully achieved. It aimed at developing a 4D innovative numerical simulation tool dedicated to the dispersion of traffic-induced air pollution at local scale on the whole urban area of PARIS. AIRCITY modeling system is based on PMSS (Parallel-Micro-SWIFT-SPRAY) software, which has been developed by ARIA Technologies in close collaboration with CEA and MOKILI. PMSS is a simplified CFD solution which is an alternative to micro-scale simulations usually carried out with full-CFD. Yet, AIRCITY challenge was to model the flow and pollutant dispersion with a 3 m resolution over the whole city of Paris covering a 14 km × 11,5 km domain. Thus, the choice was to run a mass-consistent diagnostic flow model (SWIFT) associated with a Lagrangian Particle Dispersion Model (SPRAY) on a massively parallel architecture. With a 3 m resolution on this huge domain, parallelization was applied to the computation of both the flow (by domain splitting) and the Lagrangian dispersion (management of particles is split over several processors). This MPI parallelization is more complex but gives a large flexibility to optimize the number of CPU, the available RAM and the CPU time. So, it makes possible to process arbitrarily large domains (only limited by the memory of the available nodes). As CEA operates the largest computing center in Europe, with parallel machines ranging from a few hundred to several thousand cores, the modeling system was tested on huge parallel clusters. More usual and affordable computers with a few tens of cores were also utilized during the project by ARIA Technologies and by AIRPARIF, the Regional Air Quality Management Board of Paris region, whose role was also to build the end-users requirements. These computations were performed on a simulation domain restricted to the hypercenter of Paris with dimensions around 2 km × 2 km (at the same resolution of 3 m). The focus was on the improvements needed to adapt simulation codes initially designed for emergency response to urban air quality applications: • Coupling with the MM5 / CHIMERE operational photochemical model at AIRPARIF (as the forecast background), • Turbulence generated by traffic / coupling with traffic model, • Inclusion of chemical reactions / Interaction with background substances (especially NO / NO2). Finally, in-depth validation of the modeling system was undertaken using both the routine air quality measurements in Paris (at four stations influenced by the road traffic) and a field experiment specially arranged for the project, with LIDARs provided by LEOSPHERE Inc. Comparison of PMSS and measurements gave excellent results concerning NO / NO2 and PM10 hourly concentrations for a monthly period of time while the LIDAR campaign results were also promising. In the paper, more details are given regarding the modeling system principles and developments and its validation. Perspectives of the project will also be discussed as AIRCITY system. The TRL must now be elevated from a demonstration to a robust and systematically validated modeling tool that could be used to predict routinely the air quality in Paris and in other large cities around the world.

Download Full-text

Pollutant transport in coastal areas with and without background wind

Annales Geophysicae ◽

10.1007/s00585-997-0476-5 ◽

1997 ◽

Vol 15 (4) ◽

pp. 476-486 ◽

Cited By ~ 1

Author(s):

J. Camps ◽

J. Massons ◽

M. R. Soler ◽

E. C. Nickerson

Keyword(s):

Large Scale ◽

Dispersion Model ◽

Three Dimensional ◽

Coastal Region ◽

Coupled Model ◽

Pollutant Dispersion ◽

Particle Dispersion ◽

Background Wind ◽

Meteorological Model ◽

Pollutant Concentrations

Abstract. A three-dimensional meteorological model and a Lagrangian particle dispersion model are used to study the effects of a uniform large-scale wind on the dispersion of a non-reactive pollutant in a coastal region with complex terrain. Simulations are carried out both with and without a background wind. A comparison between model results and measured data (wind and pollutant concentrations) indicates that the coupled model system provides a useful mechanism for analyzing pollutant dispersion in coastal regions.

Download Full-text

Contrasting local and long-range-transported warm ice-nucleating particles during an atmospheric river in coastal California, USA

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-4193-2019 ◽

2019 ◽

Vol 19 (7) ◽

pp. 4193-4210 ◽

Cited By ~ 5

Author(s):

Andrew C. Martin ◽

Gavin Cornwell ◽

Charlotte M. Beall ◽

Forest Cannon ◽

Sean Reilly ◽

...

Keyword(s):

Long Range ◽

Dispersion Model ◽

Particle Dispersion ◽

Mixed Phase ◽

Dispersion Modeling ◽

Time Resolved ◽

Atmospheric Rivers ◽

Atmospheric River ◽

Cloud Properties ◽

The Impact

Abstract. Ice-nucleating particles (INPs) have been found to influence the amount, phase and efficiency of precipitation from winter storms, including atmospheric rivers. Warm INPs, those that initiate freezing at temperatures warmer than −10 ∘C, are thought to be particularly impactful because they can create primary ice in mixed-phase clouds, enhancing precipitation efficiency. The dominant sources of warm INPs during atmospheric rivers, the role of meteorology in modulating transport and injection of warm INPs into atmospheric river clouds, and the impact of warm INPs on mixed-phase cloud properties are not well-understood. In this case study, time-resolved precipitation samples were collected during an atmospheric river in northern California, USA, during winter 2016. Precipitation samples were collected at two sites, one coastal and one inland, which are separated by about 35 km. The sites are sufficiently close that air mass sources during this storm were almost identical, but the inland site was exposed to terrestrial sources of warm INPs while the coastal site was not. Warm INPs were more numerous in precipitation at the inland site by an order of magnitude. Using FLEXPART (FLEXible PARTicle dispersion model) dispersion modeling and radar-derived cloud vertical structure, we detected influence from terrestrial INP sources at the inland site but did not find clear evidence of marine warm INPs at either site. We episodically detected warm INPs from long-range-transported sources at both sites. By extending the FLEXPART modeling using a meteorological reanalysis, we demonstrate that long-range-transported warm INPs were observed only when the upper tropospheric jet provided transport to cloud tops. Using radar-derived hydrometeor classifications, we demonstrate that hydrometeors over the terrestrially influenced inland site were more likely to be in the ice phase for cloud temperatures between 0 and −10 ∘C. We thus conclude that terrestrial and long-range-transported aerosol were important sources of warm INPs during this atmospheric river. Meteorological details such as transport mechanism and cloud structure were important in determining (i) warm INP source and injection temperature and (ii) ultimately the impact of warm INPs on mixed-phase cloud properties.

Download Full-text

Mesoscale circulations over complex terrain in the Valencia coastal region, Spain – Part 2: Modeling CO<sub>2</sub> transport using idealized surface fluxes

Atmospheric Chemistry and Physics ◽

10.5194/acp-7-1851-2007 ◽

2007 ◽

Vol 7 (7) ◽

pp. 1851-1868 ◽

Cited By ~ 58

Author(s):

G. Pérez-Landa ◽

P. Ciais ◽

G. Gangoiti ◽

J. L. Palau ◽

A. Carrara ◽

...

Keyword(s):

Complex Terrain ◽

Transport Model ◽

Mesoscale Model ◽

Atmospheric Transport ◽

Dispersion Model ◽

Coastal Region ◽

Net Ecosystem Exchange ◽

Co2 Concentration ◽

Particle Dispersion ◽

Surface Fluxes

Abstract. Vertical profiles of CO2 concentration were collected during an intensive summer campaign in a coastal complex-terrain region within the frame of the European Project RECAB (Regional Assessment and Modelling of the Carbon Balance in Europe). The region presents marked diurnal mesoscale circulation patterns. These circulations result in a specific coupling between atmospherically transported CO2 and its surface fluxes. To understand the effects of this interaction on the spatial variability of the observed CO2 concentrations, we applied a high-resolution transport simulation to an idealized model of land biotic fluxes. The regional Net Ecosystem Exchange fluxes were extrapolated for different land-use classes by using a set of eddy-covariance measurements. The atmospheric transport model is a Lagrangian particle dispersion model, driven by a simulation of the RAMS mesoscale model. Our simulations were able to successfully reproduce some of the processes controlling the mesoscale transport of CO2. A semi-quantitative comparison between simulations and data allowed us to characterize how the coupling between mesoscale transport and surface fluxes produced CO2 spatial gradients in the domain. Temporal averages in the simulated CO2 field show a covariance between flux and transport consisting of: 1) horizontally, a CO2 deficit over land, mirrored by a CO2 excess over the sea and 2) vertically, the prevalence of a mean CO2 depletion between 500 and 2000 m, and a permanent build-up of CO2 in the lower levels.

Download Full-text

Assessment of Lagrangian particle dispersion model “LAPMOD” through short range field tracer test in complex terrain

Journal of Environmental Radioactivity ◽

10.1016/j.jenvrad.2019.04.015 ◽

2019 ◽

Vol 205-206 ◽

pp. 34-41 ◽

Cited By ~ 1

Author(s):

Amin ul Haq ◽

Qaisar Nadeem ◽

Amjad Farooq ◽

Naseem Irfan ◽

Masroor Ahmad ◽

...

Keyword(s):

Complex Terrain ◽

Short Range ◽

Dispersion Model ◽

Tracer Test ◽

Particle Dispersion ◽

Lagrangian Particle

Download Full-text

A Multiscale Numerical Modeling Study of Smoke Dispersion and the Ventilation Index in Southwestern Colorado

Atmosphere ◽

10.3390/atmos11080846 ◽

2020 ◽

Vol 11 (8) ◽

pp. 846

Author(s):

Michael T. Kiefer ◽

Joseph J. Charney ◽

Shiyuan Zhong ◽

Warren E. Heilman ◽

Xindi Bian ◽

...

Keyword(s):

Residence Time ◽

Prescribed Fire ◽

Dispersion Model ◽

Diagnostic Value ◽

Particle Dispersion ◽

Spatiotemporal Variability ◽

Grid Spacing ◽

Particle Residence Time ◽

Smoke Dispersion ◽

Horizontal Grid

The ventilation index (VI) is an index that describes the potential for smoke or other pollutants to disperse from a source. In this study, a Lagrangian particle dispersion model was utilized to examine smoke dispersion and the diagnostic value of VI during a September 2018 prescribed fire in southwestern Colorado. Smoke dispersion in the vicinity of the fire was simulated using the FLEXPART-WRF particle dispersion model, driven by meteorological outputs from Advanced Regional Prediction System (ARPS) simulations of the background (non-fire) conditions. Two research questions are posed: (1) Is a horizontal grid spacing of 4 km comparable to the finest grid spacing currently used in operational weather models and sufficient to capture the spatiotemporal variability in wind and planetary boundary layer (PBL) structure during the fire? (2) What is the relationship between VI and smoke dispersion during the prescribed fire event, as measured by particle residence time within a given horizontal or vertical distance from each particle’s release point? The ARPS no-fire simulations are shown to generally reproduce the observed variability in weather variables, with greatest fidelity to observations found with horizontal grid spacing of approximately 1 km or less. It is noted that there are considerable differences in particle residence time (i.e., dispersion) at different elevations, with VI exhibiting greater diagnostic value in the southern half of the domain, farthest from the higher terrain across the north. VI diagnostic value is also found to vary temporally, with diagnostic value greatest during the mid-morning to mid-afternoon period, and lowest during thunderstorm outflow passage in the late afternoon. Results from this study are expected to help guide the application of VI in complex terrain, and possibly inform development of new dispersion potential metrics.

Download Full-text

Air-Quality Challenges of Prescribed Fire in the Complex Terrain and Wildland Urban Interface Surrounding Bend, Oregon

Atmosphere ◽

10.3390/atmos10090515 ◽

2019 ◽

Vol 10 (9) ◽

pp. 515 ◽

Cited By ~ 2

Author(s):

Colton Miller ◽

Susan O’Neill ◽

Miriam Rorig ◽

Ernesto Alvarado

Keyword(s):

Complex Terrain ◽

Dispersion Model ◽

Weather Data ◽

Dispersion Modeling ◽

Prescribed Fires ◽

National Forest ◽

Modeling Framework ◽

Wildland Urban Interface ◽

Meteorological Model ◽

Smoke Dispersion

Prescribed fires in forest ecosystems can negatively impact human health and safety by transporting smoke downwind into nearby communities. Smoke transport to communities is known to occur around Bend, Oregon, United States of America (USA), where burning at the wildland–urban interface in the Deschutes National Forest resulted in smoke intrusions into populated areas. The number of suitable days for prescribed fires is limited due to the necessity for moderate weather conditions, as well as wind directions that do not carry smoke into Bend. To better understand the conditions leading to these intrusions and to assess predictions of smoke dispersion from prescribed fires, we collected data from an array of weather and particulate monitors over the autumn of 2014 and spring of 2015 and historical weather data from nearby remote automated weather stations (RAWS). We characterized the observed winds to compare with meteorological and smoke dispersion models using the BlueSky smoke modeling framework. The results from this study indicated that 1–6 days per month in the spring and 2–4 days per month in the fall met the general meteorological prescription parameters for conducting prescribed fires in the National Forest. Of those, 13% of days in the spring and 5% of days in the fall had “ideal” wind patterns, when north winds occurred during the day and south winds did not occur at night. The analysis of smoke intrusions demonstrated that dispersion modeling can be useful for anticipating the timing and location of smoke impacts, but substantial errors in wind speed and direction of the meteorological models can lead to mischaracterizations of intrusion events. Additionally, for the intrusion event modeled using a higher-resolution 1-km meteorological and dispersion model, we found improved predictions of both the timing and location of smoke delivery to Bend compared with the 4-km meteorological model. The 1-km-resolution model prediction fell within 1 h of the observed event, although with underpredicted concentrations, and demonstrated promise for high-resolution modeling in areas of complex terrain.

Download Full-text

Mesoscale circulations over complex terrain in the Valencia coastal region, Spain, Part 2: linking CO<sub>2</sub> surface fluxes with observed concentrations

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-6-2853-2006 ◽

2006 ◽

Vol 6 (2) ◽

pp. 2853-2895 ◽

Cited By ~ 4

Author(s):

G. Pérez-Landa ◽

P. Ciais ◽

G. Gangoiti ◽

J. L. Palau ◽

A. Carrara ◽

...

Keyword(s):

Diurnal Cycle ◽

Complex Terrain ◽

Mesoscale Model ◽

Dispersion Model ◽

Particle Dispersion ◽

Surface Fluxes ◽

Rectification Effect ◽

Mesoscale Circulations ◽

Area Of Interest ◽

Co2 Concentrations

Abstract. Several consecutive vertical profiles of CO2 concentration and meteorological parameters were collected during an intensive summer campaign in a coastal complex terrain region within the frame of the European Project RECAB (Regional Assessment and Modelling of the Carbon Balance in Europe). The region presents a marked diurnal cycle in the wind flow (analyzed in detail in a companion paper) as a consequence of the development of mesoscale circulations. In terms of the different stages of the diurnal cycle in the meteorology, these circulations result in an important coupling between atmospheric transport and surface CO2 fluxes. To understand the effects of this interaction on the spatial variability of the observed CO2 concentrations, we conduct a high-resolution simulation with a coupled biosphere-atmosphere model in the area of interest during a representative case study. Our model approach consists of estimating the regional NEE distribution by using a set of eddy-covariance measurements that are transported by a mesoscale model coupled to a Lagrangian particle dispersion model. Our simulations were able to successfully reproduce crucial processes controlling the mesoscale transport of CO2. Availability of both simulations and observations for our analysis allowed us to characterize the influence of the coupling between mesoscale circulations and biological processes in the spatial gradients of the CO2 concentrations. Temporal averages in the simulated CO2 distribution show a 3-D rectification effect consisting of: 1) horizontally, a CO2 deficit over land, mirrored by a CO2 excess over the sea and 2) vertically, the prevalence of mean CO2 depletion between 500 and 2000 m, and the permanent build-up of CO2 in the lower levels.

Download Full-text

Microsatellite Analysis and Urediniospore Dispersal Simulations Support the Movement of Puccinia graminis f. sp. tritici from Southern Africa to Australia

Phytopathology ◽

10.1094/phyto-04-18-0110-r ◽

2019 ◽

Vol 109 (1) ◽

pp. 133-144 ◽

Cited By ~ 12

Author(s):

Botma Visser ◽

Marcel Meyer ◽

Robert F. Park ◽

Christopher A. Gilligan ◽

Laura E. Burgin ◽

...

Keyword(s):

South African ◽

Southern Africa ◽

Dispersion Model ◽

Meteorological Data ◽

Particle Dispersion ◽

Dispersion Modeling ◽

Puccinia Graminis ◽

Wheat Stem Rust ◽

Long Distance ◽

Dispersal Events

The Australian wheat stem rust (Puccinia graminis f. sp. tritici) population was shaped by the introduction of four exotic incursions into the country. It was previously hypothesized that at least two of these (races 326-1,2,3,5,6 and 194-1,2,3,5,6 first detected in 1969) had an African origin and moved across the Indian Ocean to Australia on high-altitude winds. We provide strong supportive evidence for this hypothesis by combining genetic analyses and complex atmospheric dispersion modeling. Genetic analysis of 29 Australian and South African P. graminis f. sp. tritici races using microsatellite markers confirmed the close genetic relationship between the South African and Australian populations, thereby confirming previously described phenotypic similarities. Lagrangian particle dispersion model simulations using finely resolved meteorological data showed that long distance dispersal events between southern Africa and Australia are indeed possible, albeit rare. Simulated urediniospore transmission events were most frequent from central South Africa (viable spore transmission on approximately 7% of all simulated release days) compared with other potential source regions in southern Africa. The study acts as a warning of possible future P. graminis f. sp. tritici dispersal events from southern Africa to Australia, which could include members of the Ug99 race group, emphasizing the need for continued surveillance on both continents.

Download Full-text