scholarly journals Parameterizations for convective transport in various cloud-topped boundary layers

2015 ◽  
Vol 15 (7) ◽  
pp. 10709-10738 ◽  
Author(s):  
M. Sikma ◽  
H. G. Ouwersloot
Keyword(s):  
Large Scale ◽  
Convective Transport ◽  
Area Fraction ◽  
Cloud Base ◽  
Accurate Estimation ◽  
Large Eddy Simulation Model ◽  
Wide Range ◽  
Scale Models ◽  
Upward Velocity ◽  
Independent Variable

Abstract. We investigate the representation of convective transport of atmospheric compounds that can be applied in large-scale models. We focus on three key parameterizations that, when combined, express this transport: the area fraction of transporting clouds, the upward velocity in the cloud cores and the chemical concentrations at the cloud base. The first two parameterizations combined represent the mass flux by clouds. To investigate the key parameterizations under a wide range of conditions, we use Large-Eddy Simulation model data for 10 meteorological situations, characterized by either shallow cumulus or stratocumulus clouds. In the analysis of the area fraction of clouds, we (i) simplify the independent variable used for the parameterization, Q1, by considering the variability in moisture rather than in the saturation deficit. We show that there is an unambiguous dependence of the area fraction of clouds on the simplified Q1, and update the parameters in the parameterization to account for this simplification. We (ii) further demonstrate that the independent variable has to be evaluated locally to capture cloud presence. Furthermore, we (iii) show that the area fraction of transporting clouds is not represented by the parameterization for the total cloud area fraction, as is currently applied in large-scale models. To capture cloud transport, a novel active cloud area fraction parameterization is proposed. Subsequently, the scaling of the upward velocity in the clouds' core by the Deardorff convective velocity scale and the parameterization for the concentration of atmospheric reactants at cloud base from literature are verified and improved by analyzing 6 SCu cases. For the latter, we additionally discuss how the parameterization is affected by wind conditions. This study contributes to a more accurate estimation of convective transport in large-scale models, which occurs there at sub-grid scale.

scholarly journals Parameterizations for convective transport in various cloud-topped boundary layers

2015 ◽  
Vol 15 (18) ◽  
pp. 10399-10410 ◽  
Author(s):  
M. Sikma ◽  
H. G. Ouwersloot
Keyword(s):  
Boundary Layer ◽  
Convective Transport ◽  
Area Fraction ◽  
Cloud Base ◽  
Accurate Estimation ◽  
Shallow Cumulus ◽  
Wide Range ◽  
Upward Velocity ◽  
Independent Variable ◽  
Cloud Cores

Abstract. We investigate the representation of convective transport of atmospheric compounds by boundary layer clouds. We focus on three key parameterizations that, when combined, express this transport: the area fraction of transporting clouds, the upward velocity in the cloud cores and the chemical concentrations at cloud base. The first two parameterizations combined represent the kinematic mass flux by clouds. To investigate the key parameterizations under a wide range of conditions, we use large-eddy simulation model data for 10 meteorological situations, characterized by either shallow cumulus or stratocumulus clouds. The parameterizations have not been previously tested with such large data sets. In the analysis, we show that the parameterization of the area fraction of clouds currently used in mixed-layer models is affected by boundary layer dynamics. Therefore, we (i) simplify the independent variable used for this parameterization, Q1, by considering the variability in moisture rather than in the saturation deficit and update the parameters in the parameterization to account for this simplification. We (ii) next demonstrate that the independent variable has to be evaluated locally to capture cloud presence. Furthermore, we (iii) show that the area fraction of transporting clouds is not represented by the parameterization for the total cloud area fraction, as is currently assumed in literature. To capture cloud transport, a novel active cloud area fraction parameterization is proposed. Subsequently, the scaling of the upward velocity in cloud cores by the Deardorff convective velocity scale and the parameterization for the concentration of atmospheric reactants at cloud base from literature are verified and improved by analysing six shallow cumulus cases. For the latter, we additionally discuss how the parameterization is affected by wind conditions. This study contributes to a more accurate estimation of convective transport, which occurs at sub-grid scales.

scholarly journals Efficient parameterization of large-scale dynamic models based on relative measurements

2019 ◽  
Author(s):  
Leonard Schmiester ◽  
Yannik Schälte ◽  
Fabian Fröhlich ◽  
Jan Hasenauer ◽  
Daniel Weindl
Keyword(s):  
Large Scale ◽  
Dynamic Models ◽  
Error Model ◽  
Supplementary Information ◽  
Reaction Networks ◽  
Model Parameters ◽  
Biological Processes ◽  
Wide Range ◽  
Scale Models ◽  
Relative Measurements

Abstract Motivation Mechanistic models of biochemical reaction networks facilitate the quantitative understanding of biological processes and the integration of heterogeneous datasets. However, some biological processes require the consideration of comprehensive reaction networks and therefore large-scale models. Parameter estimation for such models poses great challenges, in particular when the data are on a relative scale. Results Here, we propose a novel hierarchical approach combining (i) the efficient analytic evaluation of optimal scaling, offset and error model parameters with (ii) the scalable evaluation of objective function gradients using adjoint sensitivity analysis. We evaluate the properties of the methods by parameterizing a pan-cancer ordinary differential equation model (>1000 state variables, >4000 parameters) using relative protein, phosphoprotein and viability measurements. The hierarchical formulation improves optimizer performance considerably. Furthermore, we show that this approach allows estimating error model parameters with negligible computational overhead when no experimental estimates are available, providing an unbiased way to weight heterogeneous data. Overall, our hierarchical formulation is applicable to a wide range of models, and allows for the efficient parameterization of large-scale models based on heterogeneous relative measurements. Availability and implementation Supplementary code and data are available online at http://doi.org/10.5281/zenodo.3254429 and http://doi.org/10.5281/zenodo.3254441. Supplementary information Supplementary data are available at Bioinformatics online.

scholarly journals Gsmodutils: A python based framework for test-driven genome scale metabolic model development

2018 ◽  
Author(s):  
James P Gilbert ◽  
Nicole Pearcy ◽  
Rupert Norman ◽  
Thomas Millat ◽  
Klaus Winzer ◽  
...  
Keyword(s):  
Open Source ◽  
Large Scale ◽  
Model Development ◽  
Metabolic Model ◽  
Validation Data ◽  
Engineering Research ◽  
Modelling Framework ◽  
Wide Range ◽  
Scale Models ◽  
Genome Scale

AbstractMotivationGenome scale metabolic models (GSMMs) are increasingly important for systems biology and metabolic engineering research as they are capable of simulating complex steady-state behaviour. Constraints based models of this form can include thousands of reactions and metabolites, with many crucial pathways that only become activated in specific simulation settings. However, despite their widespread use, power and the availability of tools to aid with the construction and analysis of large scale models, little methodology is suggested for the continued management of curated large scale models. For example, when genome annotations are updated or new understanding regarding behaviour of is discovered, models often need to be altered to reflect this. This is quickly becoming an issue for industrial systems and synthetic biotechnology applications, which require good quality reusable models integral to the design, build and test cycle.ResultsAs part of an ongoing effort to improve genome scale metabolic analysis, we have developed a test-driven development methodology for the continuous integration of validation data from different sources. Contributing to the open source technology based around COBRApy, we have developed thegsmodutilsmodelling framework placing an emphasis on test-driven design of models through defined test cases. Crucially, different conditions are configurable allowing users to examine how different designs or curation impact a wide range of system behaviours, minimising error between model versions.AvailabilityThe software framework described within this paper is open source and freely available fromhttp://github.com/SBRCNottingham/gsmodutils

scholarly journals The prevalence of precipitation from polar supercooled clouds

2021 ◽  
Vol 21 (5) ◽  
pp. 3949-3971
Author(s):  
Israel Silber ◽  
Ann M. Fridlind ◽  
Johannes Verlinde ◽  
Andrew S. Ackerman ◽  
Grégory V. Cesana ◽  
...  
Keyword(s):  
Large Scale ◽  
Microwave Radiometer ◽  
Detection Sensitivity ◽  
Cloud Formation ◽  
The Arctic ◽  
Ice Formation ◽  
Cloud Base ◽  
Energy Budgets ◽  
Polar Regions ◽  
Scale Models

Abstract. Supercooled clouds substantially impact polar surface energy budgets, but large-scale models often underestimate their occurrence, which motivates accurately establishing metrics of basic processes. An analysis of long-term measurements at Utqiaġvik, Alaska, and McMurdo Station, Antarctica, combines lidar-validated use of soundings to identify supercooled cloud layers and colocated ground-based profiling radar measurements to quantify cloud base precipitation. We find that more than 85 % (75 %) of sampled supercooled layers are precipitating over the Arctic (Antarctic) site, with more than 75 % (50 %) precipitating continuously to the surface. Such high frequencies can be reconciled with substantially lesser spaceborne estimates by considering differences in radar hydrometeor detection sensitivity. While ice precipitation into supercooled clouds from aloft is common, we also find that the great majority of supercooled cloud layers without ice falling into them are themselves continuously generating precipitation. Such sustained primary ice formation is consistent with continuous activation of immersion-mode ice-nucleating particles (INPs), suggesting that supercooled cloud formation is a principal gateway to ice formation at temperatures greater than ∼-38 ∘C over polar regions. The prevalence of weak precipitation fluxes is also consistent with supercooled cloud longevity and with well-observed and widely simulated case studies. An analysis of colocated microwave radiometer retrievals suggests that weak precipitation fluxes can be nonetheless consequential to moisture budgets for supercooled clouds owing to small liquid water paths. The results here also demonstrate that the observed abundance of mixed-phase clouds can vary substantially with instrument sensitivity and methodology. Finally, we suggest that these ground-based precipitation rate statistics offer valuable guidance for improving the representation of polar cloud processes in large-scale models.

Study on Estimation of Flow Around Marine Propeller by Large-Scale LES and Affection of Grid Resolution and Reynolds Number

2020 ◽  
Author(s):  
Takeharu Fujisawa ◽  
Makoto Tsubokura ◽  
Hisao Tanaka
Keyword(s):  
Reynolds Number ◽  
Numerical Methods ◽  
Large Scale ◽  
Operating Conditions ◽  
Grid Resolution ◽  
Estimation Accuracy ◽  
Accurate Estimation ◽  
Scale Models ◽  
Rans Models ◽  
Ship Performance

Abstract To develop a ship with higher propulsion performance, accurate estimation method is required. Tthe performance of ships is estimated by both experimental methods using scale models and numerical methods based on computational fluid dynamics (CFD) using Reynolds average Navier-Stokes equation (RANS) models. Experiments with scale models have limitations regarding fast execution and cost reduction due to physical constraints, and we believe it is important to improve numerical methods. Adjustment of turbulent models can improve the estimation accuracy of numerical methods, but it is necessary to continuously compare and verify the numerical and experimental results. There is a limit to the improvement of the estimation accuracy of the numerical method with RANS models. Direct numerical simulation (DNS), which can be solved without modeling the turbulence field, can acquire an accurate flow field, but it is difficult to implement because it requires a huge number of grids. In a large eddy simulation (LES) model, if the grid resolution (filter size) is fine, the limitations imposed by the model itself are reduced. LES performed with a sufficiently fine grid resolution may be able to achieve the comparable estimation accuracy as DNS without a high computational load. We considered this method to be promising for accurately estimating ship performance. This is an initial study of a ship performance estimation calculation method using large-scale LES. We performed LES calculations with up to 6.4 billion cells for propeller open water test and obtained basic knowledge about large-scale LES calculations. We carried out calculations with different grid resolutions under the same operating conditions, and with different Reynolds numbers at the same resolution to show how the grid resolution and Reynolds number affect the estimation of propeller performance and flow around the propeller.

scholarly journals The Prevalence of Precipitation from Polar Supercooled Clouds

2020 ◽  
Author(s):  
Israel Silber ◽  
Ann M. Fridlind ◽  
Johannes Verlinde ◽  
Andrew S. Ackerman ◽  
Grégory V. Cesana ◽  
...  
Keyword(s):  
Large Scale ◽  
Microwave Radiometer ◽  
Detection Sensitivity ◽  
Cloud Formation ◽  
The Arctic ◽  
Ice Formation ◽  
Cloud Base ◽  
Energy Budgets ◽  
Polar Regions ◽  
Scale Models

Abstract. Supercooled clouds substantially impact polar surface energy budgets but large-scale models often underestimate their occurrence, which motivates accurately establishing metrics of basic processes. An analysis of long-term measurements at Utqiaġvik, Alaska, and McMurdo Station, Antarctica, combines lidar-validated use of soundings to identify supercooled cloud layers and colocated ground-based profiling radar measurements to quantify cloud base precipitation. We find that more than 85 % (75 %) of sampled supercooled layers are precipitating over the Arctic (Antarctic) site, with more than 75 % (50 %) precipitating continuously to the surface. Such high frequencies can be reconciled with substantially lesser spaceborne estimates by considering differences in radar hydrometeor detection sensitivity. While ice precipitation into supercooled clouds from aloft is common, we also find that the great majority of supercooled cloud layers without ice falling into them are themselves continuously generating precipitation. Such sustained primary ice formation is consistent with continuous activation of immersion-mode ice nucleating particles (INPs), suggesting that supercooled cloud formation is a principal gateway to ice formation at temperatures greater than ~ −38 °C over polar regions. The prevalence of weak precipitation fluxes is also consistent with supercooled cloud longevity, and with well-observed and widely simulated case studies. An analysis of colocated microwave radiometer retrievals suggests that weak precipitation fluxes can be nonetheless consequential to moisture budgets for supercooled clouds owing to small liquid water paths. Finally, we suggest that these ground-based precipitation rate statistics offer valuable guidance for improving the representation of polar cloud processes in large-scale models.

scholarly journals Evaluating Boundary Layer–Based Mass Flux Closures Using Cloud-Resolving Model Simulations of Deep Convection

2010 ◽  
Vol 67 (7) ◽  
pp. 2212-2225 ◽  
Author(s):  
Jennifer K. Fletcher ◽  
Christopher S. Bretherton
Keyword(s):  
Boundary Layer ◽  
Mass Flux ◽  
Large Scale ◽  
Deep Convection ◽  
Cloud Base ◽  
Cumulus Convection ◽  
Model Simulations ◽  
Shallow Cumulus ◽  
Wide Range ◽  
Cloud Resolving Model

Abstract High-resolution three-dimensional cloud resolving model simulations of deep cumulus convection under a wide range of large-scale forcings are used to evaluate a mass flux closure based on boundary layer convective inhibition (CIN) that has previously been applied in parameterizations of shallow cumulus convection. With minor modifications, it is also found to perform well for deep oceanic and continental cumulus convection, and it matches simulated cloud-base mass flux much better than a closure based only on the boundary layer convective velocity scale. CIN closure maintains an important feedback among cumulus base mass flux, compensating subsidence, and CIN that keeps the boundary layer top close to cloud base. For deep convection, the proposed CIN closure requires prediction of a boundary layer mean turbulent kinetic energy (TKE) and a horizontal moisture variance, both of which are strongly correlated with precipitation. For our cases, CIN closure predicts cloud-base mass flux in deep convective environments as well as the best possible bulk entraining CAPE closure, but unlike the latter, CIN closure also works well for shallow cumulus convection without retuning of parameters.

scholarly journals Efficient parameterization of large-scale dynamic models based on relative measurements

2019 ◽  
Author(s):  
Leonard Schmiester ◽  
Yannik Schälte ◽  
Fabian Fröhlich ◽  
Jan Hasenauer ◽  
Daniel Weindl
Keyword(s):  
Large Scale ◽  
Error Model ◽  
Supplementary Information ◽  
Reaction Networks ◽  
Model Parameters ◽  
Biological Processes ◽  
Link Type ◽  
Wide Range ◽  
Scale Models ◽  
Relative Measurements

AbstractMotivationMechanistic models of biochemical reaction networks facilitate the quantitative understanding of biological processes and the integration of heterogeneous datasets. However, some biological processes require the consideration of comprehensive reaction networks and therefore large-scale models. Parameter estimation for such models poses great challenges, in particular when the data are on a relative scale.ResultsHere, we propose a novel hierarchical approach combining (i) the efficient analytic evaluation of optimal scaling, offset, and error model parameters with (ii) the scalable evaluation of objective function gradients using adjoint sensitivity analysis. We evaluate the properties of the methods by parameterizing a pan-cancer ordinary differential equation model (>1000 state variables,>4000 parameters) using relative protein, phospho-protein and viability measurements. The hierarchical formulation improves optimizer performance considerably. Furthermore, we show that this approach allows estimating error model parameters with negligible computational overhead when no experimental estimates are available, pro-viding an unbiased way to weight heterogeneous data. Overall, our hierarchical formulation is applicable to a wide range of models, and allows for the efficient parameterization of large-scale models based on heterogeneous relative measurements.Contactjan.hasenauer@helmholtz-muenchen.deSupplementary informationSupplementary information are available atbioRxivonline. Supplementary code and data are available online athttp://doi.org/10.5281/zenodo.2593839andhttp://doi.org/10.5281/zenodo.2592186.

Electron microscopy study of reactively sputter-deposited Ti/N films on silicon

1992 ◽  
Vol 50 (2) ◽  
pp. 1362-1363
Author(s):  
V. C. Kannan ◽  
A. K. Singh ◽  
R. B. Irwin ◽  
S. Chittipeddi ◽  
F. D. Nkansah ◽  
...  
Keyword(s):  
Integrated Circuits ◽  
Large Scale ◽  
Hexagonal Phase ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Process Conditions ◽  
Tin Films ◽  
Wide Range ◽  
Fcc Phase ◽  
Circuits Vlsi

Titanium nitride (TiN) films have historically been used as diffusion barrier between silicon and aluminum, as an adhesion layer for tungsten deposition and as an interconnect material etc. Recently, the role of TiN films as contact barriers in very large scale silicon integrated circuits (VLSI) has been extensively studied. TiN films have resistivities on the order of 20μ Ω-cm which is much lower than that of titanium (nearly 66μ Ω-cm). Deposited TiN films show resistivities which vary from 20 to 100μ Ω-cm depending upon the type of deposition and process conditions. TiNx is known to have a NaCl type crystal structure for a wide range of compositions. Change in color from metallic luster to gold reflects the stabilization of the TiNx (FCC) phase over the close packed Ti(N) hexagonal phase. It was found that TiN (1:1) ideal composition with the FCC (NaCl-type) structure gives the best electrical property.

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