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- Keyword
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- Atm/Ocean Structure/ Phenomena; Boundary layer; Convective clouds; Marine boundary layer; Stratiform clouds; Physical Meteorology and Climatology; Surface fluxes; Models and modeling; Large eddy simulations (1)
- Cumulus clouds; aeroplane observations; large-eddy simulations; mass flux; downdraughts (1)
- Entrainment; Turbulence; Cumulus clouds; Thermodynamics (1)
- Stratiform clouds; Cloud forcing; Conservation equations; Energy budget/balance; Moisture/moisture budget; Thermodynamics (1)
Articles 1 - 11 of 11
Full-Text Articles in Physical Sciences and Mathematics
Turbulent Dispersion In Cloudy Boundary Layers, Remco A. Verzijlbergh, Harmen J.J. Jonker, Thijs Heus, J. Vilà-Guerau De Arellano
Turbulent Dispersion In Cloudy Boundary Layers, Remco A. Verzijlbergh, Harmen J.J. Jonker, Thijs Heus, J. Vilà-Guerau De Arellano
Thijs Heus
Compared to dry boundary layers, dispersion in cloud-topped boundary layers has received less attention. In this LES based numerical study we investigate the dispersion of a passive tracer in the form of Lagrangian particles for four kinds of atmospheric boundary layers: 1) a dry convective boundary layer (for reference), 2) a "smoke" cloud boundary layer in which the turbulence is driven by radiative cooling, 3) a stratocumulus topped boundary layer and 4) a shallow cumulus topped boundary layer. We show that the dispersion characteristics of the smoke cloud boundary layer as well as the stratocumulus situation can be well understood …
Observational Validation Of The Compensating Mass Flux Through The Shell Around Cumulus Clouds, Thijs Heus, C. Freek J. Pols, Harmen J.J. Jonker, Harry E.A. Van Den Akker, Donald H. Lenschow
Observational Validation Of The Compensating Mass Flux Through The Shell Around Cumulus Clouds, Thijs Heus, C. Freek J. Pols, Harmen J.J. Jonker, Harry E.A. Van Den Akker, Donald H. Lenschow
Thijs Heus
The existence of a subsiding shell around cumulus clouds has been observed before in several aircraft measurement campaigns. Recent results from large-eddy simulations (LES) showed that the downward mass flux through the shell compensates for a significant fraction of the upward mass flux through the cloud. In this study, aeroplane measurements from the Rain In Cumulus over the Ocean (RICO) field campaign are used to verify the existence of this compensating mass flux. Just as in the LES results, the in-shell downward mass flux is found to be significant. However, a few differences were found in comparison with the LES …
Reconciling And Validating The Cloud Thickness And Liquid Water Path Tendencies, Mohamed S. Ghonima, Joel R. Norris, Thijs Heus, Jan Kleissl
Reconciling And Validating The Cloud Thickness And Liquid Water Path Tendencies, Mohamed S. Ghonima, Joel R. Norris, Thijs Heus, Jan Kleissl
Thijs Heus
A detailed derivation of stratocumulus cloud thickness and liquid water path tendencies as a function of the well-mixed boundary layer mass, heat, and moisture budget equations is presented. The derivation corrects an error in the cloud thickness tendency equation derived by R. Wood to make it consistent with the liquid water path tendency equation derived by J. J. van der Dussen et al. The validity of the tendency equations is then tested against the output of large-eddy simulations of a typical stratocumulus-topped boundary layer case and is found to be in good agreement.
Large-Eddy Simulation Of Organized Precipitating Trade Wind Cumulus Clouds, Axel Seifert, Thijs Heus
Large-Eddy Simulation Of Organized Precipitating Trade Wind Cumulus Clouds, Axel Seifert, Thijs Heus
Thijs Heus
Trade wind cumulus clouds often organize in along-wind cloud streets and across-wind mesoscale arcs. We present a benchmark large-eddy simulation which resolves the individual clouds as well as the mesoscale organization on scales of O(10 km). Different methods to quantify organization of cloud fields are applied and discussed. Using perturbed physics large-eddy simulation experiments, the processes leading to the formation of cloud clusters and the mesoscale arcs are revealed. We find that both cold pools as well as the sub-cloud layer moisture field are crucial to understand the organization of precipitating shallow convection. Further sensitivity studies show that microphysical assumptions …
Formulation Of The Dutch Atmospheric Large-Eddy Simulation (Dales) And Overview Of Its Applications, Thijs Heus, C. C. Van Heerwaarden, Harmen J.J. Jonker, A. Pier Siebesma, S. Axelsen, K. Van Den Dries, O. Geoffroy, A. F. Moene, D. Pino, S. R. De Roode, J. Vilà-Guerau De Arellano
Formulation Of The Dutch Atmospheric Large-Eddy Simulation (Dales) And Overview Of Its Applications, Thijs Heus, C. C. Van Heerwaarden, Harmen J.J. Jonker, A. Pier Siebesma, S. Axelsen, K. Van Den Dries, O. Geoffroy, A. F. Moene, D. Pino, S. R. De Roode, J. Vilà-Guerau De Arellano
Thijs Heus
The current version of the Dutch Atmospheric Large-Eddy Simulation (DALES) is presented. DALES is a large-eddy simulation code designed for studies of the physics of the atmospheric boundary layer, including convective and stable boundary layers as well as cloudy boundary layers. In addition, DALES can be used for studies of more specific cases, such as flow over sloping or heterogeneous terrain, and dispersion of inert and chemically active species. This paper contains an extensive description of the physical and numerical formulation of the code, and gives an overview of its applications and accomplishments in recent years.
Factors Controlling Stratocumulus Cloud Lifetime Over Coastal Land, Mohamed S. Ghonima, Thijs Heus, Joel R. Norris, Jan Kleissl
Factors Controlling Stratocumulus Cloud Lifetime Over Coastal Land, Mohamed S. Ghonima, Thijs Heus, Joel R. Norris, Jan Kleissl
Thijs Heus
The breakup of stratocumulus clouds over coastal land areas is studied using a combination of large-eddy simulations (LESs) and mixed-layer models (MLMs) with a focus on mechanisms regulating the timing of the breakup. In contrast with stratocumulus over ocean, strong sensible heat flux over land prevents the cloud layer from decoupling during day. As the cloud thins during day, turbulence generated by surface flux becomes larger than turbulence generated by longwave cooling across the cloud layer. To capture this shift in turbulence generation in the MLM, an existing entrainment parameterization is extended. The MLM is able to mimic cloud evolution …
Direct Numerical Simulation Of Evaporative Cooling At The Lateral Boundary Of Shallow Cumulus Clouds, Dick Abma, Thijs Heus, Juan Pedro Mellado
Direct Numerical Simulation Of Evaporative Cooling At The Lateral Boundary Of Shallow Cumulus Clouds, Dick Abma, Thijs Heus, Juan Pedro Mellado
Thijs Heus
This study investigates the dynamics of the subsiding shell at the lateral boundary of cumulus clouds, focusing on the role of evaporative cooling. Since the size of this shell is well below what large-eddy simulations can resolve, the authors have performed direct numerical simulations of an idealized subsiding shell. The system develops a self-similar, Reynolds number–independent flow that allows for the determination of explicit scaling laws relating the characteristic length, time, and velocity scales of the shell. It is found that the shell width grows quadratically in time, linearly with the traveled distance. The magnitude of these growth rates shows …
Fluctuations In A Quasi-Stationary Shallow Cumulus Cloud Ensemble, M. Sakradzija, Axel Seifert, Thijs Heus
Fluctuations In A Quasi-Stationary Shallow Cumulus Cloud Ensemble, M. Sakradzija, Axel Seifert, Thijs Heus
Thijs Heus
We propose an approach to stochastic parameterisation of shallow cumulus clouds to represent the convective variability and its dependence on the model resolution. To collect information about the individual cloud lifecycles and the cloud ensemble as a whole, we employ a large eddy simulation (LES) model and a cloud tracking algorithm, followed by conditional sampling of clouds at the cloud-base level. In the case of a shallow cumulus ensemble, the cloud-base mass flux distribution is bimodal, due to the different shallow cloud subtypes, active and passive clouds. Each distribution mode can be approximated using a Weibull distribution, which is a …
Automated Tracking Of Shallow Cumulus Clouds In Large Domain, Long Duration Large Eddy Simulations, Thijs Heus, Axel Seifert
Automated Tracking Of Shallow Cumulus Clouds In Large Domain, Long Duration Large Eddy Simulations, Thijs Heus, Axel Seifert
Thijs Heus
This paper presents a method for feature tracking of fields of shallow cumulus convection in large eddy simulations (LES) by connecting the projected cloud cover in space and time, and by accounting for splitting and merging of cloud objects. Existing methods tend to be either imprecise or, when using the full three-dimensional (3-D) spatial field, prohibitively expensive for large data sets. Compared to those 3-D methods, the current method reduces the memory footprint by up to a factor 100, while retaining most of the precision by correcting for splitting and merging events between different clouds. The precision of the algorithm …
A Statistical Approach To The Life Cycle Analysis Of Cumulus Clouds Selected In A Virtual Reality Environment, Thijs Heus, Harmen J.J. Jonker, Harry E.A. Van Den Akker, Eric J. Griffith, Michal Koutek, Frits H. Post
A Statistical Approach To The Life Cycle Analysis Of Cumulus Clouds Selected In A Virtual Reality Environment, Thijs Heus, Harmen J.J. Jonker, Harry E.A. Van Den Akker, Eric J. Griffith, Michal Koutek, Frits H. Post
Thijs Heus
In this study, a new method is developed to investigate the entire life cycle of shallow cumuli in large eddy simulations. Although trained observers have no problem in distinguishing the different life stages of a cloud, this process proves difficult to automate, because cloud-splitting and cloud-merging events complicate the distinction between a single system divided in several cloudy parts and two independent systems that collided. Because the human perception is well equipped to capture and to make sense of these time-dependent three-dimensional features, a combination of automated constraints and human inspection in a three-dimensional virtual reality environment is used to …
Cgils: Results From The First Phase Of An International Project To Understand The Physical Mechanisms Of Low Cloud Feedbacks In Single Column Models, Minghua Zhang, Christopher S. Bretherton, Peter N. Blossey, Phillip H. Austin, Julio T. Bacmeister, Sandrine Bony, Florent Brient, Suvarchal K. Cheedela, Anning Cheng, Anthony D. Del Genio, Stephan R. De Roode, Satoshi Endo, Charmaine N. Franklin, Jean Christophe Golaz, Cecile Hannay, Thijs Heus
Cgils: Results From The First Phase Of An International Project To Understand The Physical Mechanisms Of Low Cloud Feedbacks In Single Column Models, Minghua Zhang, Christopher S. Bretherton, Peter N. Blossey, Phillip H. Austin, Julio T. Bacmeister, Sandrine Bony, Florent Brient, Suvarchal K. Cheedela, Anning Cheng, Anthony D. Del Genio, Stephan R. De Roode, Satoshi Endo, Charmaine N. Franklin, Jean Christophe Golaz, Cecile Hannay, Thijs Heus
Thijs Heus
CGILS—the CFMIP-GASS Intercomparison of Large Eddy Models (LESs) and single column models (SCMs)—investigates the mechanisms of cloud feedback in SCMs and LESs under idealized climate change perturbation. This paper describes the CGILS results from 15 SCMs and 8 LES models. Three cloud regimes over the subtropical oceans are studied: shallow cumulus, cumulus under stratocumulus, and well-mixed coastal stratus/stratocumulus. In the stratocumulus and coastal stratus regimes, SCMs without activated shallow convection generally simulated negative cloud feedbacks, while models with active shallow convection generally simulated positive cloud feedbacks. In the shallow cumulus alone regime, this relationship is less clear, likely due to …