scholarly journals Inherent Dissipation of Upwind‐Biased Potential Temperature Advection and its Feedback on Model Dynamics

2021 ◽  
Vol 13 (3) ◽  
Author(s):  
A. Gassmann
Keyword(s):  
Potential Temperature ◽  
Temperature Advection ◽  
Model Dynamics

scholarly journals Inherent dissipation of upwind-biased potential temperature advection and its feedback on model dynamics

2021 ◽  
Author(s):  
Almut Gaßmann
Keyword(s):  
Energy Conservation ◽  
Pressure Gradient ◽  
Potential Temperature ◽  
Gradient Term ◽  
Advection Scheme ◽  
Temperature Advection ◽  
Advection Schemes ◽  
Pressure Gradient Term ◽  
Diffusive Fluxes ◽  
Total Energy Conservation

<p>Higher order upwind biased advection schemes are often used for potential temperature advection in dynamical cores of atmospheric models. The inherent diffusive and anti-diffusive fluxes are interpreted here as the effect of irreversible sub-gridscale dynamics. For those, total energy conservation and positive internal entropy production must be guaranteed. As a consequence of energy conservation, the pressure gradient term should be formulated in Exner pressure form. The presence of local antidiffusive fluxes in potential temperature advection schemes foils the validity of the second law of thermodynamics. Due to this failure, a spurious wind acceleration into the wrong direction is locally induced via the pressure gradient term. When correcting the advection scheme to be more entropically consistent, the spurious acceleration is avoided, but two side effects come to the fore: (i) the overall accuracy of the advection scheme decreases and (ii) the now purely diffusive fluxes become more discontinuous compared to the original ones, which leads to more sudden body forces in the momentum equation. Therefore the amplitudes of excited gravity waves from jets and fronts increase compared to the original formulation with inherent local antidiffusive fluxes.</p><p>The means used for supporting the argumentation line are theoretical arguments concerning total energy conservation and internal entropy production, pure advection tests, one-dimensional advection-dynamics interaction tests and evaluation of runs with a global atmospheric dry dynamical core.</p>

scholarly journals Seasonal Changes in a Vertical Thermal Structure Producing Stable Lower-Troposphere Layers over the Inland Region of the Indochina Peninsula

2011 ◽  
Vol 24 (13) ◽  
pp. 3211-3223 ◽  
Author(s):  
Masato I. Nodzu ◽  
Shin-Ya Ogino ◽  
Manabu D. Yamanaka
Keyword(s):  
Seasonal Changes ◽  
Mixed Boundary ◽  
Thermal Structure ◽  
Potential Temperature ◽  
Lower Troposphere ◽  
Reanalysis Data ◽  
Stable Layer ◽  
Indochina Peninsula ◽  
Budget Analysis ◽  
Temperature Advection

Abstract The authors performed a thermal budget analysis to understand the nature of seasonal changes in stable lower-troposphere layers over the inland region of the Indochina Peninsula, using atmospheric reanalysis data. The analysis focuses on subseasonal stable layers. Stability increase in the generation of stable layers is classified into three dominant thermal factors: vertical differences in horizontal potential temperature advection, vertical potential temperature advection, and their residual component Q1. The largest contributor to the stability increase is defined as the dominant thermal factor. Climatological typical heights where stable layers most frequently appear are the 850–700-, 700–600-, and 600–500-hPa levels in November–January, February–March, and April, respectively, according to a previous study. From November to January, most of the stable layers in the typical height are generated by vertical differences in horizontal potential temperature advection. Their generation (dissipation) is characterized by strong (weak) cooling due to horizontal advection below the stable layers. The strong cooling is related to cold surges in the winter monsoon. Generation of the stable layers in the typical height from February to April is characterized by vertical differences in Q1. Here, Q1 cooling below the stable layers is demonstrated in February and March. The authors propose a mixed boundary layer process in explaining the Q1 cooling. In April, the analyses demonstrate Q1 heating above the stable layers, coincident with a peak in the apparent moisture sink. The results indicate that the thermal processes of stable-layer generation change the height of the stable layer along the seasonal advance.

Pitting Corrosion of Biomedical Titanium and Titanium Alloys: A Brief Review

2020 ◽  
Vol 16 ◽  
Author(s):  
Yu-Wei Cui ◽  
Liang-Yu Chen ◽  
Xin-Xin Liu
Keyword(s):  
Corrosion Resistance ◽  
Pitting Corrosion ◽  
Potential Temperature ◽  
Growth Stages ◽  
Factors Affecting ◽  
Ti Alloys ◽  
Pitting Corrosion Resistance ◽  
Superior Mechanical Properties ◽  
Good Biocompatibility ◽  
Main Factors

Abstract:: Thanks to their excellent corrosion resistance, superior mechanical properties and good biocompatibility, titanium (Ti) and Ti alloys are extensively applied in biomedical fields. Pitting corrosion is a critical consideration for the reliability of Ti and Ti alloys used in the human body. Therefore, this article focuses on the pitting corrosion of Ti and Ti alloys, which introduces the growth stages of pitting corrosion and its main influencing factors. Three stages, i.e. (1) breakdown of passive film, (1) metastable pitting, and (3) propagation of pitting, are roughly divided to introduce the pitting corrosion. As reviewed, corrosive environment, applied potential, temperature and alloy compositions are the main factors affecting the pitting corrosion of Ti and Ti alloys. Moreover, the pitting corrosion of different types Ti alloys are also reviewed to correlate the types of Ti alloys and the main factors of pitting corrosion. Roughly speaking, β-type Ti alloys have the best pitting corrosion resistance among the three types of Ti alloys.

Rotating Shallow-Water Models with Moist Convection

2018 ◽  
Author(s):  
Vladimir Zeitlin
Keyword(s):  
Baroclinic Instability ◽  
Potential Temperature ◽  
Moist Convection ◽  
Mathematical Properties ◽  
Vertical Fluxes ◽  
Equivalent Potential ◽  
Shallow Water Models ◽  
Wave Emission ◽  
Rotating Shallow Water ◽  
Convective Fluxes

It is shown how the standard RSW can be ’augmented’ to include phase transitions of water. This chapter explains how to incorporate extra (convective) vertical fluxes in the model. By using Lagrangian conservation of equivalent potential temperature condensation of the water vapour, which is otherwise a passive tracer, is included in the model and linked to convective fluxes. Simple relaxational parameterisation of condensation permits the closure of the system, and surface evaporation can be easily included. Physical and mathematical properties of thus obtained model are explained, and illustrated on the example of wave scattering on the moisture front. The model is applied to ’moist’ baroclinic instability of jets and vortices. Condensation is shown to produce a transient increase of the growth rate. Special attention is paid to the moist instabilities of hurricane-like vortices, which are shown to enhance intensification of the hurricane, increase gravity wave emission, and generate convection-coupled waves.

scholarly journals Melt volume at Atlantic volcanic rifted margins controlled by depth-dependent extension and mantle temperature

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Gang Lu ◽  
Ritske S. Huismans
Keyword(s):  
Numerical Models ◽  
Potential Temperature ◽  
Analytical Prediction ◽  
Natural Systems ◽  
Passive Margins ◽  
Margin Width ◽  
Rifted Margins ◽  
Mantle Potential Temperature ◽  
Mantle Temperature ◽  
Rifted Margin

AbstractBreakup volcanism along rifted passive margins is highly variable in time and space. The factors controlling magmatic activity during continental rifting and breakup are not resolved and controversial. Here we use numerical models to investigate melt generation at rifted margins with contrasting rifting styles corresponding to those observed in natural systems. Our results demonstrate a surprising correlation of enhanced magmatism with margin width. This relationship is explained by depth-dependent extension, during which the lithospheric mantle ruptures earlier than the crust, and is confirmed by a semi-analytical prediction of melt volume over margin width. The results presented here show that the effect of increased mantle temperature at wide volcanic margins is likely over-estimated, and demonstrate that the large volumes of magmatism at volcanic rifted margin can be explained by depth-dependent extension and very moderate excess mantle potential temperature in the order of 50–80 °C, significantly smaller than previously suggested.

scholarly journals Frequency and average gray-level information for thermal ablation status in ultrasound B-Mode sequences

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Jens Ziegle ◽  
Alfredo Illanes ◽  
Axel Boese ◽  
Michael Friebe
Keyword(s):  
Thermal Ablation ◽  
Ex Vivo ◽  
Cell Damage ◽  
Potential Temperature ◽  
Image Sequences ◽  
Target Tissue ◽  
Gray Level ◽  
Porcine Liver ◽  
Time Frequency ◽  
Average Gray Level

AbstractDuring thermal ablation in a target tissue the information about temperature is crucial for decision making of successful therapy. An observable temporal and spatial temperature propagation would give a visual feedback of irreversible cell damage of the target tissue. Potential temperature features in ultrasound (US) B-Mode image sequences during radiofrequency (RF) ablation in ex-vivo porcine liver were found and analysed. These features could help to detect the transition between reversible and irreversible damage of the ablated target tissue. Experimental RF ablations of ex-vivo porcine liver were imaged with US B-Mode imaging and image sequences were recorded. Temperature was simultaneously measured within the liver tissue around a bipolar RF needle electrode. In the B-Mode images, regions of interest (ROIs) around the centre of the measurement spots were analysed in post-processing using average gray-level (AVGL) compared against temperature. The pole of maximum energy level in the time-frequency domain of the AVGL changes was investigated in relation to the measured temperatures. Frequency shifts of the pole were observed which could be related to transitions between the states of tissue damage.

scholarly journals Global Stability Analysis of a Bioreactor Model for Phenol and Cresol Mixture Degradation

Processes ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 124
Author(s):  
Neli Dimitrova ◽  
Plamena Zlateva
Keyword(s):  
Specific Growth ◽  
Equilibrium Points ◽  
Nonlinear Ordinary Differential Equations ◽  
The Novel ◽  
Model Design ◽  
Stirred Bioreactor ◽  
Global Stability Analysis ◽  
Local Asymptotic Stability ◽  
Model Dynamics ◽  
Stability And Bifurcations

We propose a mathematical model for phenol and p-cresol mixture degradation in a continuously stirred bioreactor. The model is described by three nonlinear ordinary differential equations. The novel idea in the model design is the biomass specific growth rate, known as sum kinetics with interaction parameters (SKIP) and involving inhibition effects. We determine the equilibrium points of the model and study their local asymptotic stability and bifurcations with respect to a practically important parameter. Existence and uniqueness of positive solutions are proved. Global stabilizability of the model dynamics towards equilibrium points is established. The dynamic behavior of the solutions is demonstrated on some numerical examples.

scholarly journals Global heat balance and heat uptake in potential temperature coordinates

2021 ◽  
Author(s):  
Antoine Hochet ◽  
Rémi Tailleux ◽  
Till Kuhlbrodt ◽  
David Ferreira
Keyword(s):  
Global Warming ◽  
Water Mass ◽  
Potential Temperature ◽  
Effective Diffusion ◽  
Mitigation Strategies ◽  
Ocean Heat Uptake ◽  
Cold Temperatures ◽  
Advection Diffusion Equation ◽  
Advection Diffusion ◽  
Heat Uptake

AbstractThe representation of ocean heat uptake in Simple Climate Models used for policy advice on climate change mitigation strategies is often based on variants of the one-dimensional Vertical Advection/Diffusion equation (VAD) for some averaged form of potential temperature. In such models, the effective advection and turbulent diffusion are usually tuned to emulate the behaviour of a given target climate model. However, because the statistical nature of such a “behavioural” calibration usually obscures the exact dependence of the effective diffusion and advection on the actual physical processes responsible for ocean heat uptake, it is difficult to understand its limitations and how to go about improving VADs. This paper proposes a physical calibration of the VAD that aims to provide explicit traceability of effective diffusion and advection to the processes responsible for ocean heat uptake. This construction relies on the coarse-graining of the full three-dimensional advection diffusion for potential temperature using potential temperature coordinates. The main advantage of this formulation is that the temporal evolution of the reference temperature profile is entirely due to the competition between effective diffusivity that is always positive definite, and the water mass transformation taking place at the surface, as in classical water mass analyses literature. These quantities are evaluated in numerical simulations of present day climate and global warming experiments. In this framework, the heat uptake in the global warming experiment is attributed to the increase of surface heat flux at low latitudes, its decrease at high latitudes and to the redistribution of heat toward cold temperatures made by diffusive flux.

scholarly journals Cosmological viable f(R,T) dark energy model: dynamics and stability

2014 ◽  
Vol 356 (1) ◽  
pp. 173-180 ◽  
Author(s):  
E. H. Baffou ◽  
A. V. Kpadonou ◽  
M. E. Rodrigues ◽  
M. J. S. Houndjo ◽  
J. Tossa
Keyword(s):  
Dark Energy ◽  
Dark Energy Model ◽  
Energy Model ◽  
Model Dynamics
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