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Large-Eddy Simulation Of Organized Precipitating Trade Wind Cumulus Clouds, Axel Seifert, Thijs Heus 2019 Deutscher Wetterdienst

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 ...


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 2019 Cleveland State University

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 2019 University of California

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 2019 Max Planck Institute for Meteorology

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 ...


Fluctuations In A Quasi-Stationary Shallow Cumulus Cloud Ensemble, M. Sakradzija, Axel Seifert, Thijs Heus 2019 Max Planck Institute for Meteorology

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 2019 Cleveland State University

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 2019 Cleveland State University

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 2019 Stony Brook University

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 ...


Single-Crystal Permanent Magnets: Extraordinary Magnetic Behavior In The Ta-,Cu-, And Fe-Substituted Ceco 5 Systems, Tej N. Lamichhane, Michael T. Onyszczak, Olena Palasyuk, Saba Sharikadze, Tae-Hoon Kim, Qisheng Lin, Matthew J. Kramer, R. W. McCallum, Aleksander L. Wysocki, Manh Cuong Nguyen, Vladimir P. Antropov, Tribhuwan Pandey, David Parker, Sergey L. Bud’ko, Paul C. Canfield, Andriy Palasyuk 2019 Iowa State University and Ames Laboratory

Single-Crystal Permanent Magnets: Extraordinary Magnetic Behavior In The Ta-,Cu-, And Fe-Substituted Ceco 5 Systems, Tej N. Lamichhane, Michael T. Onyszczak, Olena Palasyuk, Saba Sharikadze, Tae-Hoon Kim, Qisheng Lin, Matthew J. Kramer, R. W. Mccallum, Aleksander L. Wysocki, Manh Cuong Nguyen, Vladimir P. Antropov, Tribhuwan Pandey, David Parker, Sergey L. Bud’Ko, Paul C. Canfield, Andriy Palasyuk

Qisheng Lin

To reduce material and processing costs of commercial permanent magnets and to attempt to fill the empty niche of energy products, 10–20 MGOe, between low-flux (ferrites, alnico) and high-flux (Nd2Fe14B- and SmCo5-type) magnets, we report the synthesis, structure, magnetic properties, and modeling of Ta-, Cu-, and Fe-substituted CeCo5. Using a self-flux technique, we grow single crystals of Ce15.1Ta1.0Co74.4Cu9.5, Ce16.3Ta0.6Co68.9Cu14.2, Ce15.7Ta0.6Co67.8Cu15.9, Ce16.3Ta0.3Co61.7Cu21.7, and Ce14.3Ta1.0Co62.0Fe12.3Cu10.4. X-ray-diffraction analysis shows that these materials retain a CaCu5 substructure and incorporate small amounts of ...


Mg Assisted Flux Growth And Characterization Of Single Crystalline Sm2co17, Tej Nath Lamichhane, Qisheng Lin, Valentin Taufour, Andriy Palasyuk, Tribhuwan Pandey, David Parker, Sergey L. Bud’ko, Paul C. Canfield 2019 Iowa State University and Ames Laboratory

Mg Assisted Flux Growth And Characterization Of Single Crystalline Sm2co17, Tej Nath Lamichhane, Qisheng Lin, Valentin Taufour, Andriy Palasyuk, Tribhuwan Pandey, David Parker, Sergey L. Bud’Ko, Paul C. Canfield

Qisheng Lin

This paper presents details of Mg-assisted flux growth of Sm2Co17 single crystals in a Ta crucible well below the melting temperature of binary Sm2Co17. Both the crushed single crystalline powder x-ray diffraction (XRD) and single crystalline XRD data revealed the Th2Zn17 type rhombohedral(R-3m) crystal structure. Ta atom is found to be statistically replacing the Co-Co dumbbell with its position being at the center of the dumbbell. The Curie temperature of our lightly Mg and Ta doped Sm2Co17 sample is determined to be ∼1100 K using method of generalized Bloch law fitting of easy axis spontaneous magnetization data.


Single-Crystal Permanent Magnets: Extraordinary Magnetic Behavior In The Ta-,Cu-, And Fe-Substituted Ceco 5 Systems, Tej N. Lamichhane, Michael T. Onyszczak, Olena Palasyuk, Saba Sharikadze, Tae-Hoon Kim, Qisheng Lin, Matthew J. Kramer, R. W. McCallum, Aleksander L. Wysocki, Manh Cuong Nguyen, Vladimir P. Antropov, Tribhuwan Pandey, David Parker, Sergey L. Bud’ko, Paul C. Canfield, Andriy Palasyuk 2019 Iowa State University and Ames Laboratory

Single-Crystal Permanent Magnets: Extraordinary Magnetic Behavior In The Ta-,Cu-, And Fe-Substituted Ceco 5 Systems, Tej N. Lamichhane, Michael T. Onyszczak, Olena Palasyuk, Saba Sharikadze, Tae-Hoon Kim, Qisheng Lin, Matthew J. Kramer, R. W. Mccallum, Aleksander L. Wysocki, Manh Cuong Nguyen, Vladimir P. Antropov, Tribhuwan Pandey, David Parker, Sergey L. Bud’Ko, Paul C. Canfield, Andriy Palasyuk

Paul C. Canfield

To reduce material and processing costs of commercial permanent magnets and to attempt to fill the empty niche of energy products, 10–20 MGOe, between low-flux (ferrites, alnico) and high-flux (Nd2Fe14B- and SmCo5-type) magnets, we report the synthesis, structure, magnetic properties, and modeling of Ta-, Cu-, and Fe-substituted CeCo5. Using a self-flux technique, we grow single crystals of Ce15.1Ta1.0Co74.4Cu9.5, Ce16.3Ta0.6Co68.9Cu14.2, Ce15.7Ta0.6Co67.8Cu15.9, Ce16.3Ta0.3Co61.7Cu21.7, and Ce14.3Ta1.0Co62.0Fe12.3Cu10.4. X-ray-diffraction analysis shows that these materials retain a CaCu5 substructure and incorporate small amounts of ...


Equation Of State Of Boron Nitride Combining Computation, Modeling, And Experiment, Shuai Zhang, Amy Lazicki, Burkhard Militzer, Lin H. Yang, Kyle Caspersen, Jim A. Gaffney, Markus W. Däne, John E. Pask, Walter R. Johnson, Abhiraj Sharma, Phanish Suryanarayana, Duane D. Johnson, Andrey V. Smirnov, Philip A. Sterne, David Erskine, Richard A. London, Federica Coppari, Damian Swift, Joseph Nilsen, Art J. Nelson, Heather D. Whitley 2019 Lawrence Livermore National Laboratory

Equation Of State Of Boron Nitride Combining Computation, Modeling, And Experiment, Shuai Zhang, Amy Lazicki, Burkhard Militzer, Lin H. Yang, Kyle Caspersen, Jim A. Gaffney, Markus W. Däne, John E. Pask, Walter R. Johnson, Abhiraj Sharma, Phanish Suryanarayana, Duane D. Johnson, Andrey V. Smirnov, Philip A. Sterne, David Erskine, Richard A. London, Federica Coppari, Damian Swift, Joseph Nilsen, Art J. Nelson, Heather D. Whitley

Duane D. Johnson

The equation of state (EOS) of materials at warm dense conditions poses significant challenges to both theory and experiment. We report a combined computational, modeling, and experimental investigation leveraging new theoretical and experimental capabilities to investigate warm-dense boron nitride (BN). The simulation methodologies include path integral Monte Carlo (PIMC), several density functional theory (DFT) molecular dynamics methods [plane-wave pseudopotential, Fermi operator expansion (FOE), and spectral quadrature (SQ)], activity expansion (actex), and all-electron Green's function Korringa-Kohn-Rostoker (mecca), and compute the pressure and internal energy of BN over a broad range of densities and temperatures. Our experiments were conducted at the ...


Anisotropy Induced Vortex Lattice Rearrangement In Cakfe4as4, Rustem Khasanov, William R. Meier, Sergey L. Bud’ko, Hubertus Luetkens, Paul C. Canfield, Alex Amato 2019 Paul Scherrer Institut

Anisotropy Induced Vortex Lattice Rearrangement In Cakfe4as4, Rustem Khasanov, William R. Meier, Sergey L. Bud’Ko, Hubertus Luetkens, Paul C. Canfield, Alex Amato

Paul C. Canfield

The magnetic penetration depth anisotropy gamma(lambda) = lambda(c)/lambda(ab) (lambda(ab) and lambda(c) are the in-plane and the out-of-plane components of the magnetic penetration depth) in a CaKFe4As4 single crystal sample (the critical temperature T-c similar or equal to 35 K) was studied by means of muon-spin rotation (mu SR). gamma(lambda) is almost temperature independent for T less than or similar to 20 K (gamma(lambda) similar or equal to 1.9) and it reaches similar or equal to 3.0 by approaching T-c. The change of gamma(lambda) induces the corresponding rearrangement of the flux ...


Single Pair Of Weyl Fermions In The Half-Metallic Semimetal Eucd2as2, Lin-Lin Wang, Na Hyun Jo, Brinda Kuthanazhi, Yun Wu, Robert J. McQueeney, Adam Kaminski, Paul C. Canfield 2019 Ames Laboratory

Single Pair Of Weyl Fermions In The Half-Metallic Semimetal Eucd2as2, Lin-Lin Wang, Na Hyun Jo, Brinda Kuthanazhi, Yun Wu, Robert J. Mcqueeney, Adam Kaminski, Paul C. Canfield

Ames Laboratory Accepted Manuscripts

Materials with the ideal case of a single pair of Weyl points (WPs) are highly desirable for elucidating the unique properties of Weyl fermions. EuC d 2 A s 2 is an antiferromagnetic topological insulator or Dirac semimetal depending on the different magnetic configurations. Using first-principles band-structure calculations, we show that inducing ferromagnetism in EuC d 2 A s 2 can generate a single pair of WPs from splitting the single pair of antiferromagnetic Dirac points due to its half-metallic nature. Analysis with a low-energy effective Hamiltonian shows that a single pair of WPs is obtained in EuC d 2 ...


Magnetic Structure And Magnetization Of Z -Axis Helical Heisenberg Antiferromagnets With Xy Anisotropy In High Magnetic Fields Transverse To The Helix Axis At Zero Temperature, David C. Johnston 2019 Iowa State University and Ames Laboratory

Magnetic Structure And Magnetization Of Z -Axis Helical Heisenberg Antiferromagnets With Xy Anisotropy In High Magnetic Fields Transverse To The Helix Axis At Zero Temperature, David C. Johnston

Ames Laboratory Accepted Manuscripts

A helix has a wave vector along the z axis with the magnetic moments ferromagnetically aligned within xy planes with a turn angle kd between the moments in adjacent planes in transverse field H=Hxˆi=0. The magnetic structure and x-axis average magnetization per spin of this system in a classical XY anisotropy field HA is studied versus kd, HA, and large Hx at zero temperature. For values of HA below a kd-dependent maximum value, the xy helix phase transitions with increasing Hx into a spin-flop (SF) phase where the ordered moments have x, y, and z components. The moments ...


Development And Long-Term Stability Of A Comprehensive Daily Qa Program For A Modern Pencil Beam Scanning (Pbs) Proton Therapy Delivery System, Suresh Rana, Jaafar Bennouna, Alonso Gutierrez 2019 Miami Cancer Institute

Development And Long-Term Stability Of A Comprehensive Daily Qa Program For A Modern Pencil Beam Scanning (Pbs) Proton Therapy Delivery System, Suresh Rana, Jaafar Bennouna, Alonso Gutierrez

Alonso Gutierrez

No abstract provided.


Development And Long-Term Stability Of A Comprehensive Daily Qa Program For A Modern Pencil Beam Scanning (Pbs) Proton Therapy Delivery System, Suresh Rana, Jaafar Bennouna, Alonso Gutierrez 2019 Miami Cancer Institute

Development And Long-Term Stability Of A Comprehensive Daily Qa Program For A Modern Pencil Beam Scanning (Pbs) Proton Therapy Delivery System, Suresh Rana, Jaafar Bennouna, Alonso Gutierrez

Jaafar Bennouna

No abstract provided.


Development And Long-Term Stability Of A Comprehensive Daily Qa Program For A Modern Pencil Beam Scanning (Pbs) Proton Therapy Delivery System, Suresh Rana, Jaafar Bennouna, Alonso Gutierrez 2019 Miami Cancer Institute

Development And Long-Term Stability Of A Comprehensive Daily Qa Program For A Modern Pencil Beam Scanning (Pbs) Proton Therapy Delivery System, Suresh Rana, Jaafar Bennouna, Alonso Gutierrez

Suresh Rana

No abstract provided.


The Magnetic Activity Of Low-Mass Stars, Tholang Mota 2019 DePaul University

The Magnetic Activity Of Low-Mass Stars, Tholang Mota

DePaul Discoveries

The purpose of this research project is to study magnetically active low mass stars using data obtained with the Kepler space telescope. A sample of low mass stars was identified in the Kepler Objects of Interest (KOI) database by selecting stars with a temperature below 3,700 K. Data was obtained from the Mikulski Archive for Space Telescopes and analyzed using the MATLAB software. Light curves showing the stellar flux vs time were generated for approximately 20 stars, and features showing stellar flares, star spots and planetary transits were identified. We found a weak relationship between magnetic activity and stellar ...


Pressure-Temperature Phase Diagram Of The Eurbfe4as4 Superconductor, Li Xiang, Sergey L. Bud’ko, Jin-Ke Bao, Duck Young Chung, Mercouri G. Kanatzidis, Paul C. Canfield 2019 Iowa State University and Ames Laboratory

Pressure-Temperature Phase Diagram Of The Eurbfe4as4 Superconductor, Li Xiang, Sergey L. Bud’Ko, Jin-Ke Bao, Duck Young Chung, Mercouri G. Kanatzidis, Paul C. Canfield

Paul C. Canfield

The pressure dependencies of the magnetic and superconducting transitions, as well as that of the superconducting upper critical field, are reported for single crystalline EuRbFe 4 As 4 . Resistance measurements were performed under hydrostatic pressures up to 6.21 GPa and in magnetic fields up to 9 T. Zero-field-cooled magnetization measurements were performed under hydrostatic pressures up to 1.24 GPa under 20 mT applied field. Superconducting transition temperature, T c , up to 6.21 GPa and magnetic transition temperature, T M , up to 1.24 GPa were obtained and a pressure-temperature phase diagram was constructed. Our results show that ...


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