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Eric J. Fetzer - One of the best experts on this subject based on the ideXlab platform.
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The Thermodynamic State of the Arctic atmosphere observed by AIRS: comparisons during the record minimum sea ice extents of 2007 and 2012
Atmospheric Chemistry and Physics, 2013Co-Authors: Abhay Devasthale, Joseph Sedlar, Torben Koenigk, Eric J. FetzerAbstract:Abstract. The record sea ice minimum (SIM) extents observed during the summers of 2007 and 2012 in the Arctic are stark evidence of accelerated sea ice loss during the last decade. Improving our understanding of the Arctic atmosphere and accurate quantification of its characteristics becomes ever more crucial, not least to improve predictions of such extreme events in the future. In this context, the Atmospheric Infrared Sounder (AIRS) instrument onboard NASA's Aqua satellite provides crucial insights due to its ability to provide 3-D information on atmospheric Thermodynamics. Here, we facilitate comparisons in the evolution of the Thermodynamic State of the Arctic atmosphere during these two SIM events using a decade-long AIRS observational record (2003–2012). It is shown that the meteorological conditions during 2012 were not extreme, but three factors of preconditioning from winter through early summer played an important role in accelerating sea ice melt. First, the marginal sea ice zones along the central Eurasian and North Atlantic sectors remained warm throughout winter and early spring in 2012 preventing thicker ice build-up. Second, the circulation pattern favoured efficient sea ice transport out of the Arctic in the Atlantic sector during late spring and early summer in 2012 compared to 2007. Third, additional warming over the Canadian archipelago and southeast Beaufort Sea from May onward further contributed to accelerated sea ice melt. All these factors may have lead the already thin and declining sea ice cover to pass below the previous sea ice extent minimum of 2007. In sharp contrast to 2007, negative surface temperature anomalies and increased cloudiness were observed over the East Siberian and Chukchi seas in the summer of 2012. The results suggest that satellite-based monitoring of atmospheric preconditioning could be a critical source of information in predicting extreme sea ice melting events in the Arctic.
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The Thermodynamic State of the Arctic atmosphere observed by AIRS: comparisons during the record minimum sea-ice extents of 2007 and 2012
Atmospheric Chemistry and Physics Discussions, 2013Co-Authors: Abhay Devasthale, Joseph Sedlar, Torben Koenigk, Eric J. FetzerAbstract:Abstract. The record sea-ice minimum (SIM) extents observed during the summers of 2007 and 2012 in the Arctic are stark evidence of accelerated sea ice loss during the last decade. Improving our understanding of the Arctic atmosphere and accurate quantification of its characteristics becomes ever more crucial, not least to improve predictions of such extreme events in the future. In this context, the Atmospheric Infrared Sounder (AIRS) instrument onboard NASA's Aqua satellite provides crucial insights due to its ability to provide 3-D information on atmospheric Thermodynamics. Here, we facilitate comparisons in the evolution of the Thermodynamic State of the Arctic atmosphere during these two SIM events using a decade long AIRS observational record (2003–2012). It is shown that the meteorological conditions during 2012 were not extreme but three factors in preconditioning from winter through early summer probably played an important role in accelerating sea-ice melt. First, the marginal sea-ice zones along the central Eurasian and North Atlantic sectors remained warm throughout winter and early spring in 2012 preventing thicker ice build-up. Second, the circulation pattern favoured efficient sea-ice transport out of the Arctic in the Atlantic sector during late spring and early summer in 2012 compared to 2007. Third, additional warming over the Canadian Archipelago and southeast Beaufort Sea from May onward further contributed to accelerated sea-ice melt. All these factors may have lead already thin and declining sea-ice cover to pass below the previous sea-ice extent minimum of 2007. In sharp contrast to 2007, negative surface temperature anomalies and increased cloudiness were observed over the East Siberian and Chukchi Seas in the summer of 2012. The results suggest that satellite-based monitoring of atmospheric preconditioning could be a critical source of information in predicting extreme sea-ice melting events in the Arctic.
Rossend Rey - One of the best experts on this subject based on the ideXlab platform.
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Thermodynamic State dependence of orientational order and rotational relaxation in carbon tetrachloride.
The Journal of chemical physics, 2008Co-Authors: Rossend ReyAbstract:Molecular dynamics simulations show that orientational correlations in carbon tetrachloride span a wide range of distances within the phases that are ordinarily described as orientationally disordered. They are long ranged in the plastic crystal phase, reach up to several solvation layers in the liquid phase, and only involve contact neighbors within the gas phase. On the contrary, short range arrangements are rather similar, with the sequence face-to-face, edge-to-face, and edge-to-edge describing the most populated relative orientations for increasing distances. In what concerns rotational relaxation, it is shown that none of the available theories is able to describe the relationship between rotational relaxation and angular velocity relaxation times for the three phases studied. This is at variance with experimental results obtained long ago for carbon tetrafluoride, which were in excellent accord with J-diffusion, but is in line with recent experimental results for deuterated methane in gas-phase mixtures.
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Reaction rate Theory approach to Thermodynamic State dependence of hydration shell exchange for Li+(Aq)
The Journal of Physical Chemistry B, 2003Co-Authors: Marco Masia, Rossend ReyAbstract:Hydration shell exchange of Li + (aq) is analyzed from the standpoint of reaction rate theory for a wide set of Thermodynamic conditions, with an emphasis on the supercritical regime, viewing the exchange as an association-dissociation process. It is found that the free energy dependence upon the reaction coordinate of the ion-water complex maintains similar features in ambient and supercritical water, in contrast with related activated processes such as ion pair association. The activation free energy increases with decreasing density (with an inflection point ca. 0.3 g/cm 3 ) although it does not parallel the strong decrease in dielectric constant that takes place, at variance with continuum theory. The substantial increase in exchange rate from ambient to supercritical conditions cannot be simply ascribed to the temperature difference, but to an interplay of temperature and Thermodynamic State dependence of the activation free energy, while the dynamic features of the exchange are substantially independent of bulk properties. The present system provides a first computational test of Transition State Theory in supercritical fluids, showing that it overestimates the rate constant by approximately a factor of 2, being slightly more successful than in ambient water.
Wenyu Zhou - One of the best experts on this subject based on the ideXlab platform.
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The impact of vertical shear on the sensitivity of tropical cyclogenesis to environmental rotation and Thermodynamic State
Journal of Advances in Modeling Earth Systems, 2015Co-Authors: Wenyu ZhouAbstract:Here, the impact of vertical wind shear on the sensitivity of tropical cyclogenesis to environmental rotation and Thermodynamic State is investigated through idealized cloud-resolving simulations of the intensification of an incipient vortex. With vertical shear, tropical cyclones intensify faster with a higher Coriolis parameter, f, irrespective of the environmental Thermodynamic State. The vertical shear develops a vertically tilted vortex, which undergoes a precession process with the midlevel vortices rotating cyclonically around the surface center. With a higher f, the midlevel vortices are able to rotate continuously against the vertical shear, leading to the realignment of the tilted vortex and rapid intensification. With a lower f, the rotation is too slow such that the midlevel vortices are advected away from the surface center and the intensification is suppressed. The parameter, Χb, measuring the effect from the low-entropy downdraft air on the boundary layer entropy, is found to be a good indicator of the environmental Thermodynamic favorability for tropical cyclogenesis in vertical shear. Without vertical shear, tropical cyclones are found to intensify faster with a lower f by previous studies. We show this dependency on f is sensitive to the environmental Thermodynamic State. The Thermodynamical favorability for convection can be measured bymore » Χm, which estimates the time it takes for surface fluxes to moisten the midtroposphere. A smaller Χm not only leads to a faster intensification due to a shorter period for moist preconditioning of the inner region but also neutralizes the faster intensification with a lower f due to enhanced peripheral convection.« less
Matthias Ihme - One of the best experts on this subject based on the ideXlab platform.
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between supercritical liquids and gases reconciling dynamic and Thermodynamic State transitions
Journal of Supercritical Fluids, 2020Co-Authors: D T Banuti, Muralikrishna Raju, Matthias IhmeAbstract:Abstract Experimental, computational, and theoretical results have shown that the notion of a homogeneous supercritical State space has to be replaced with distinct liquid-like and gas-like regions, divided by a cross-over line. Several such cross-over lines have been proposed, such as the Frenkel line, the Fisher-Widom line, and the Widom line. We use Thermodynamics arguments, molecular dynamics (MD) simulations, and experimental data to investigate the relation between these lines. This work proposes a new interpretation of the Widom line based on the curvature of the Gibbs free energy, showing that the supercritical cross-over can be evaluated as a projection of the subcritical phase transition from a liquid to an ideal gas State to supercritical conditions. We show that the cross-over across the Widom line should not be regarded as instantaneous, but instead as spreading over a finite temperature interval. The Thermodynamic character of the Widom line becomes negligible at reduced pressures p/pcr > 3 and disappears completely at higher pressures p/pcr > 10. We find evidence that measured transitions attributed to the Widom line do in fact match the Frenkel line better. In this way, we suggest a consistent view of the supercritical State space and resolve apparent contradictions.
H Nafe - One of the best experts on this subject based on the ideXlab platform.
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relationship between the partial molar and molar quantity of a Thermodynamic State function in a multicomponent mixture revisited
The Journal of Chemical Thermodynamics, 2013Co-Authors: H NafeAbstract:Abstract As far as a multicomponent mixture is concerned, different versions exist in the literature for the relationship between the partial molar and molar quantity of a Thermodynamic State function with the most prominent example of the two quantities being the activity coefficient of an arbitrary component and the excess Gibbs free energy of a mixture comprising this component. Since the relationships published so far have to a large degree been derived independently of each other and result from apparently conflicting approaches, they are still considered as separate subjects in the literature. It is demonstrated that despite this curious situation all relationships are equivalent to each other from a mathematical point of view.
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Relationship between the partial molar and molar quantity of a Thermodynamic State function in a multicomponent mixture – revisited
The Journal of Chemical Thermodynamics, 2013Co-Authors: H NafeAbstract:Abstract As far as a multicomponent mixture is concerned, different versions exist in the literature for the relationship between the partial molar and molar quantity of a Thermodynamic State function with the most prominent example of the two quantities being the activity coefficient of an arbitrary component and the excess Gibbs free energy of a mixture comprising this component. Since the relationships published so far have to a large degree been derived independently of each other and result from apparently conflicting approaches, they are still considered as separate subjects in the literature. It is demonstrated that despite this curious situation all relationships are equivalent to each other from a mathematical point of view.
