Cedrick Ansorge
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View article: Wind Veer and Speed in Turbulent Ekman Flow Part I: Scaling Analysis and Velocity Profile Model
Wind Veer and Speed in Turbulent Ekman Flow Part I: Scaling Analysis and Velocity Profile Model Open
The profiles of wind speed and direction in turbulent Ekman flow are formulated based on asymptotic theory and data from direct numerical simulation. The profile of the streamwise component, considered in a wall-stress-aligned reference fr…
View article: Wind Veer and Speed in Turbulent Ekman Flow–Part II: Comparison to LES for Atmospheric Reynolds Numbers
Wind Veer and Speed in Turbulent Ekman Flow–Part II: Comparison to LES for Atmospheric Reynolds Numbers Open
The atmospheric boundary layer is characterized by a logarithmic increase in wind speed within the surface layer and a turning of the wind vector aloft. The simplest canonical configuration featuring both a logarithmic layer and wind turni…
View article: Surface Roughness in Stratified Turbulent Ekman Flow
Surface Roughness in Stratified Turbulent Ekman Flow Open
The interplay of surface roughness and stable stratification is investigated by direct numerical simulation of Ekman flow. Our setup is well within the turbulent regime, reaching a friction Reynolds number of $$Re_\tau \approx 2700$$ …
View article: Simulation and scaling analysis of periodic surfaces with small-scale roughness in turbulent Ekman flow
Simulation and scaling analysis of periodic surfaces with small-scale roughness in turbulent Ekman flow Open
Roughness of the surface underlying the atmospheric boundary layer causes departures of the near-surface scalar and momentum transport in comparison with aerodynamically smooth surfaces. Here, we investigate the effect of $56\times 56$ hom…
View article: Comparison of Wind profile models across the Ekman layer
Comparison of Wind profile models across the Ekman layer Open
Knowledge of the wind profile in the planetary boundary layer is key to many applications from wind power engineering via boundary-layer schemes in the atmosphere to PBL closure in large- and mesoscale models. In this presentation, we will…
View article: Open access Data Sets of Vertical Profiles for Turbulent Ekman Flow generated by DNS tlab code
Open access Data Sets of Vertical Profiles for Turbulent Ekman Flow generated by DNS tlab code Open
In the pursuit of advancing our comprehension of the atmospheric boundary layer and the associated exchange processes near the surface, the accessibility of high-quality data assumes a pivotal role. An open-access approach is acknowledged …
View article: Simulation and scaling analysis of small-scale roughness in neutrally and stably stratified turbulent Ekman flow
Simulation and scaling analysis of small-scale roughness in neutrally and stably stratified turbulent Ekman flow Open
Atmospheric flows virtually always occur over rough surfaces, which enhances the drag, mixing and vertical transport of pollutants and moisture in the atmospheric boundary layer (ABL). During nighttime, when the absence of solar radiation …
View article: Turbulence generation by unresolved orography
Turbulence generation by unresolved orography Open
Slope flows, resulting from the interplay between buoyancy and gravitational forces, are well-known to govern a plethora of local weather phenomena. In particular, orographic features and the associated surface roughness can induce turbule…
View article: Invited review Comment on egusphere-2023-1071
Invited review Comment on egusphere-2023-1071 Open
Abstract. We present BoundaryLayerDynamics.jl, a new code for turbulence-resolving simulations of atmospheric boundary-layer flows as well as canonical turbulent flows in channel geometries. The code performs direct numerical simulation as…
View article: Direct Numerical Simulation of the Aerodynamically Rough Atmospheric Boundary Layer
Direct Numerical Simulation of the Aerodynamically Rough Atmospheric Boundary Layer Open
<p>Direct numerical simulation (DNS) of the atmospheric boundary layer (ABL) is becoming more and more popular for its conceptual simplicity and increasing degree of realism: domain sizes and simulation durations can be attained that…
View article: Direct Numerical Simulation of the Aerodynamically Rough Atmospheric Boundary Layer &#8211; Implementation of an Immersed Boundary Method for Turbulent Ekman Flow
Direct Numerical Simulation of the Aerodynamically Rough Atmospheric Boundary Layer – Implementation of an Immersed Boundary Method for Turbulent Ekman Flow Open
<p>Direct numerical simulation (DNS) of the atmospheric boundary layer (ABL) is becoming more and more popular for its conceptual simplicity and increasing degree of realism: domain sizes and simulation durations can be attained that…
View article: The coldest days of MOSAiC &#8211; an LES study&#160;
The coldest days of MOSAiC – an LES study  Open
<p>The polar-night stable boundary layer, observed during MOSAiC, gives rise to extreme stabilities not found in typical mid-latitude SBLs. In a steady or near-steady synoptic environment, the boundary layer even attains a quasi-stea…
View article: Wind veer and wind speed in turbulent Ekman flow
Wind veer and wind speed in turbulent Ekman flow Open
<p>The profiles of wind speed and direction in turbulent Ekman flow are formulated based on asymptotic theory and data from direct numerical simulation. The profile of the streamwise component follows the classical viscous, logarithm…
View article: Geometry and organization of coherent structures in stably stratified atmospheric boundary layers
Geometry and organization of coherent structures in stably stratified atmospheric boundary layers Open
Global intermittency is observed in the stably stratified Atmospheric Boundary Layer (ABL) and corresponds to having large nonturbulent flow regions to develop in an otherwise turbulent flow. In this paper, the differences between continuo…
View article: Geometry and organization of coherent structures in stably stratified\n atmospheric boundary layers
Geometry and organization of coherent structures in stably stratified\n atmospheric boundary layers Open
Global intermittency is observed in the stably stratified Atmospheric\nBoundary Layer (ABL) and corresponds to having large nonturbulent flow regions\nto develop in an otherwise turbulent flow. In this paper, the differences\nbetween conti…
View article: Cloud-Top Entrainment in Mixed-Phase Stratocumulus and Its Process-Level Representation in Large-Eddy Simulation
Cloud-Top Entrainment in Mixed-Phase Stratocumulus and Its Process-Level Representation in Large-Eddy Simulation Open
Cloud-top entrainment is a crucial process for the evolution of stratocumulus and is driven by interactions of radiation, microphysics, and turbulence on scales reaching down to less than one meter. Regardless of this fact, most large-eddy…
View article: Modelling multi-scale atmosphere and land-surface interactions
Modelling multi-scale atmosphere and land-surface interactions Open
<p>As land-surface properties are heterogeneous over a broad range of length-scales, surface-induced fluxes are heterogeneous too. Representing land-surface heterogeneity and the corresponding fluxes is a challenging task in numerica…
View article: An Idealized Description for the Diurnal Cycle of the Dry Atmospheric Boundary Layer
An Idealized Description for the Diurnal Cycle of the Dry Atmospheric Boundary Layer Open
We present a conceptual model for the diurnal cycle of the dry atmospheric boundary layer (ABL). It may serve as a framework for future numerical studies on the transitional dynamics that characterize the ABL over land. The conceptual mode…
View article: Topological descriptors of spatial coherence in a convective boundary layer
Topological descriptors of spatial coherence in a convective boundary layer Open
The interaction between a turbulent convective boundary layer (CBL) and the underlying land surface is an important research problem in the geosciences. In order to model this interaction adequately, it is necessary to develop tools which …
View article: LES of Arctic mixed-phase Stratocumulus (ACLOUD RF13)
LES of Arctic mixed-phase Stratocumulus (ACLOUD RF13) Open
This data was created via three horizontally different resolved large-eddy simulations (35.0m, 10.0m, 3.5m) where the vertical resolution is below 5.0m within the atmospheric boundary layer and gradually increases to 20.0m at model top of …
View article: Scale Dependence of Atmosphere–Surface Coupling Through Similarity Theory
Scale Dependence of Atmosphere–Surface Coupling Through Similarity Theory Open
Monin–Obukhov similarity theory (MOST) applies for homogeneous and stationary conditions but is used in ever more complex and heterogeneous configurations. Here, it is used to estimate the surface friction velocity $$u_\star $$ from the wi…
View article: Parameters for the Collapse of Turbulence in the Stratified Plane Couette Flow
Parameters for the Collapse of Turbulence in the Stratified Plane Couette Flow Open
We perform direct numerical simulation of the Couette flow as a model for the stable boundary layer. The flow evolution is investigated for combinations of the (bulk) Reynolds number and the imposed surface buoyancy flux. First, we establi…
View article: The role of noise in self-organized decision making by the true slime mold Physarum polycephalum
The role of noise in self-organized decision making by the true slime mold Physarum polycephalum Open
Self-organized mechanisms are frequently encountered in nature and known to achieve flexible, adaptive control and decision-making. Noise plays a crucial role in such systems: It can enable a self-organized system to reliably adapt to shor…
View article: Analyses of external and global intermittency in the logarithmic layer of Ekman flow
Analyses of external and global intermittency in the logarithmic layer of Ekman flow Open
Existence of non-turbulent flow patches in the vicinity of the wall of a turbulent flow is known as global intermittency. Global intermittency challenges the conventional statistics approach when describing turbulence in the inner layer an…