Consistent Boundary Conditions for Age Calculations

Deleersnijder, Éric; Draoui, Insaf; Lambrechts, Jonathan; Legat, Vincent; Mouchet, Anne

doi:10.3390/w12051274

Cited by 10 publications

(7 citation statements)

References 116 publications

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“…The transport terms in both equations are discretized with a flux-limited linear advection scheme providing positivity preserving solutions for c and α. It must be noted, however, that for the mean-particle age a computed as the quotient of α and c, positivity of the solution is generally not guaranteed unless a more strict flux-limiting criterion is used (Deleersnijder et al, 2020).…”

Section: Model Descriptionmentioning

confidence: 99%

Air pollution trapping in the Dresden Basin induced by natural and urban topography

Weger

Heinold

2023

Preprint

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Abstract. The microscale variability of urban air pollution is essentially driven by the interaction between meteorology and urban topography, which remains challenging to represent spatially accurately and computationally efficiently in urban dispersion models. Natural topography can additionally exert a considerable amplifying effect on urban background pollution, depending on atmospheric stability. This requires an equally important representation in models, as even subtle terrain-height variations can enforce characteristic local flow regimes. In this model study, the effects of urban and natural topography on the local winds and air pollution dispersion in the Dresden Basin in the Eastern German Elbe valley are investigated. A new, efficient urban microscale model is used within a multiscale air-quality modeling framework. The simulations that consider real meteorological and emission conditions focus on two periods in late winter and early summer, respectively, as well as on black carbon (BC), a key air pollutant mainly emitted from motorized traffic. As a complement to the commonly used mass concentrations, the particle-age content (age concentration) is simulated. This concept, which was originally developed to study hydrological reservoir flows in an Eulerian framework, is adapted here for the first time for atmospheric boundary-layer modeling. The approach is used to identify stagnant or recirculating orographic air flows and resulting air pollution trapping. An empirical orthogonal function (EOF) analysis is applied to the simulation results to attribute the air pollution modes to specific weather patterns and quantify their significance. Air quality monitoring data for the region are used for model evaluation. The model results show a strong sensitivity to atmospheric conditions, but generally confirm increased BC levels in Dresden due to the valley location. The horizontal variability of mass concentrations is dominated by the patterns of traffic emissions, which overlay potential orography-driven pollutant accumulations. Therefore, an assessment of the orographic impact on air pollution is usually inconclusive. However, using the age concentration metric, which filters out direct emission effects, previously undetected spatial patterns are discovered that are largely modulated by the surface orography. The comparison with a dispersion simulation assuming spatially homogeneous emissions also proves the robustness of the orographic flow information contained in the age concentrations distribution and shows it to be a suitable metric to assess orographic air-pollution trapping. The simulation analysis indicates several air quality hotspots on the south-western slopes of the Dresden Basin and in the southern side valley, the Döhlen Basin, depending on the prevailing wind direction.

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Section: Model Descriptionmentioning

confidence: 99%

Air pollution trapping in the Dresden Basin induced by natural and urban topography

Weger

Heinold

2023

Preprint

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“…Deleersnijder et al [7] investigate the boundary conditions for age calculations. In CART, the mean age is computed as the ratio of the "age concentration" to the concentration of a numerical tracer.…”

Section: Timescale-focused Contributionsmentioning

confidence: 99%

“…Furthermore, this intensive data-generating capacity enriches our awareness and understanding of individual processes operating over a broad range of spatial and temporal scales, but the net effect-the "upshot"-of those processes and their interactions may be challenging to identify. Techniques for distilling, simplifying, and extracting the essence from large, complex environmental datasets have arguably never been more necessary [5][6][7].…”

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confidence: 99%

“…Both are tools that can paint a simplified, digestible (yet quantitative; [6]) picture of a large number of reactive transport processes that co-exist and interact in aquatic environments. These techniques thereby help us understand and interpret those processes, identifying the most crucial ones and establishing causal relationships between them [6,7]. The contributions to this Special Issue relate to one or both of these commonly related tools, providing new methodologies, applications, or reviews of tracers or timescales in fluid mechanics.…”

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confidence: 99%

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Tracers and Timescales: Tools for Distilling and Simplifying Complex Fluid Mechanical Problems

Lucas

Deleersnijder

2021

Water

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“…The age of a water particle is set to zero at the moment it enters the domain through inlet Γ in . The incoming-flux condition reads [36]:…”

Section: Water Age Distribution Functionmentioning

confidence: 99%

Age of Water Particles as a Diagnosis of Steady-State Flows in Shallow Rectangular Reservoirs

Dewals

Archambeau

Bruwier

et al. 2020

Water

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The age of a water particle in a shallow man-made reservoir is defined as the time elapsed since it entered it. Analyzing this diagnostic timescale provides valuable information for optimally sizing and operating such structures. Here, the constituent-oriented age and residence time theory (CART) is used to obtain not only the mean age, but also the water age distribution function at each location. The method is applied to 10 different shallow reservoirs of simple geometry (rectangular), in a steady-state framework. The results show that complex, multimodal water age distributions are found, implying that focusing solely on simple statistics (e.g., mean or median age) fails to reflect the complexity of the actual distribution of water age. The latter relates to the fast or slow pathways that water particles may take for traveling from the inlet to the outlet of the reservoirs.

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Consistent Boundary Conditions for Age Calculations

Cited by 10 publications

References 116 publications

Air pollution trapping in the Dresden Basin induced by natural and urban topography

Air pollution trapping in the Dresden Basin induced by natural and urban topography

Tracers and Timescales: Tools for Distilling and Simplifying Complex Fluid Mechanical Problems

Age of Water Particles as a Diagnosis of Steady-State Flows in Shallow Rectangular Reservoirs

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