Advection errors in an orthogonal terrain‐following coordinate: idealized 2‐D experiments using steep terrains

Zou, Xun; Li, Yiyuan; Li, Jinxi; Wang, Bin

doi:10.1002/asl.650

Cited by 4 publications

(6 citation statements)

References 27 publications

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“…In this coordinate system, the horizontal transport of aerosols is too efficient in the lowest model layers—even at times when in reality there is no transport in the layer below the MUK station. This causes overestimation in the lowest model levels of mountainous areas and is the reason why we use the height‐matched level (Li et al, ; Zou et al, , and references therein). However, the height‐matched level also has some errors as the terrain following vertical coordinate levels combined with the hydrostatic model does not produce enough vertical transport at mountainous regions.…”

Section: Resultsmentioning

confidence: 99%

Driving Factors of Aerosol Properties Over the Foothills of Central Himalayas Based on 8.5 Years Continuous Measurements

et al. 2018

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This study presents analysis of in situ measurements conducted over the period 2005-2014 in the Indian Himalayas to give a thorough overview of the factors and causes that drive aerosol properties. Aerosol extensive properties (namely, particle number concentration, scattering coefficient, equivalent black carbon, PM 2.5 , and PM 10 ) have 1.5-2 times higher values in the early to late afternoon than during the night, and a strong seasonality. The interannual variability is ±20% for both PM 2.5 and total particle number concentration. Analysis of the data shows statistically significant decreasing trends of À2.3 μg m À3 year À1 and À2.7 μg m À3 year À1 for PM 2.5 and PM 10 , respectively, over the study period. The mountainous terrain site (Mukteshwar, MUK) is primarily under the influence of air from the plains. This is due to convective transport processes that are enhanced by local and mesoscale topography, leading to pronounced valley/mountain winds and consequently to atmospheric boundary layer air lifting from the plains below. The transport from plains is evident in seasonal-diurnal patterns observed at MUK. The timing of the patterns corresponds with changes in turbulence and water vapor (q). According to our analysis, using these as proxies is a viable method for examining boundary layer influence in the absence of direct atmospheric boundary layer height measurements. Comparing the measurements with climate models shows that even regional climate models have problems capturing the orographic influence accurately at MUK, highlighting the importance of long-term direct measurements at multiple points to understand aerosol behavior in mountainous areas.

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Section: Resultsmentioning

confidence: 99%

Driving Factors of Aerosol Properties Over the Foothills of Central Himalayas Based on 8.5 Years Continuous Measurements

et al. 2018

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“…Zou et al [27] verified that increasingly higher terrain crests, which result in steeper terrain profiles (Figure 8), can induce larger advection errors in TF meshes. However, the proposed adaptive meshes are affected only by the given tagging levels and the Hessian matrix of specific variables (e.g., the tracer concentration in this study).…”

Section: Case Iv: Advection Tests With Different Types Of Terrainsmentioning

confidence: 96%

“…Here, λ = 32 km is used for the one-crest bell-shaped terrain while λ = 8 km is used for the five-crest Shär-type wavelike terrain h 5 (x). The Zou-type ten-crest wavelike terrain [27] is defined as follows:…”

Section: Case Iv: Advection Tests With Different Types Of Terrainsmentioning

confidence: 99%

“…The temporal and spatial adaptation of meshes ensures that the number of nodes and the corresponding computational costs used for all three types remain almost the same. However, for the cut-cell and TF meshes, the number of nodes should be linked to the wavenumber (Cases IV and V, see details in [27,28]). Although the area of the tracer is small compared to the computational domain, high-resolution meshes are required to achieve the increasing accuracy over the entire domain due to the fixed meshes.…”

Section: Mesh Refinement and Central Processing Unit (Cpu) Costmentioning

confidence: 99%

“…Moreover, Shaw and Weller [5] confirmed that the advection accuracy depends on the alignment of the velocity field with the VLs, indicating that a TF coordinate should be able to effectively simulate TF advection processes, while the cut-cell method is preferred for horizontal advection problems. Finally, Zou et al [27] demonstrated that advection errors are affected by the complexity of the terrain; that is, for steeper terrains, TF coordinates will induce larger advection errors. Consequently, it may be difficult to find a coordinate that is suitable for all types of meteorological flows [6].…”

Section: Introductionmentioning

confidence: 99%

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Performance of Adaptive Unstructured Mesh Modelling in Idealized Advection Cases over Steep Terrains

Zheng

Zhu

et al. 2018

Atmosphere

Self Cite

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Advection errors are common in basic terrain-following (TF) coordinates. Numerous methods, including the hybrid TF coordinate and smoothing vertical layers, have been proposed to reduce the advection errors. Advection errors are affected by the directions of velocity fields and the complexity of the terrain. In this study, an unstructured adaptive mesh together with the discontinuous Galerkin finite element method is employed to reduce advection errors over steep terrains. To test the capability of adaptive meshes, five two-dimensional (2D) idealized tests are conducted. Then, the results of adaptive meshes are compared with those of cut-cell and TF meshes. The results show that using adaptive meshes reduces the advection errors by one to two orders of magnitude compared to the cut-cell and TF meshes regardless of variations in velocity directions or terrain complexity. Furthermore, adaptive meshes can reduce the advection errors when the tracer moves tangentially along the terrain surface and allows the terrain to be represented without incurring in severe dispersion. Finally, the computational cost is analyzed. To achieve a given tagging criterion level, the adaptive mesh requires fewer nodes, smaller minimum mesh sizes, less runtime and lower proportion between the node numbers used for resolving the tracer and each wavelength than cut-cell and TF meshes, thus reducing the computational costs.

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Optimized Vertical Layers for the Hybrid Terrain-Following Coordinate Minimizing Numerical Errors in a 2D Rising Bubble Experiment near Steep Terrain

Yang,

Li,

Wang

2023

J Meteorol Res

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Advection errors in an orthogonal terrain‐following coordinate: idealized 2‐D experiments using steep terrains

Cited by 4 publications

References 27 publications

Driving Factors of Aerosol Properties Over the Foothills of Central Himalayas Based on 8.5 Years Continuous Measurements

Driving Factors of Aerosol Properties Over the Foothills of Central Himalayas Based on 8.5 Years Continuous Measurements

Performance of Adaptive Unstructured Mesh Modelling in Idealized Advection Cases over Steep Terrains

Optimized Vertical Layers for the Hybrid Terrain-Following Coordinate Minimizing Numerical Errors in a 2D Rising Bubble Experiment near Steep Terrain

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