The Experts below are selected from a list of 180 Experts worldwide ranked by ideXlab platform
Thérèse Encrenaz - One of the best experts on this subject based on the ideXlab platform.
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Revisiting the Sulfur‐Water Chemical System in the Middle Atmosphere of Venus
Journal of Geophysical Research: Planets, 2020Co-Authors: Wencheng D. Shao, Xi Zhang, Carver J. Bierson, Thérèse EncrenazAbstract:Sulfur-water chemistry plays an important role in the Middle Atmosphere of Venus. Ground based observations have found that simultaneously observed SO2 and H2O at ~64 km vary with time and are temporally anti-correlated. To understand these observations, we explore the sulfur-water chemical system using a one-dimensional chemistry-diffusion model. We find that SO2 and H2O mixing ratios above the clouds are highly dependent on mixing ratios of the two species at the Middle cloud top (58 km). The behavior of sulfur-water chemical system can be classified into three regimes but there is no abrupt transition among these regimes. In particular, there is no bifurcation behavior as previously claimed. We also find that the SO2 self-shielding effect causes H2O above the clouds to respond to the Middle cloud top in a non-monotonic fashion. Through comparison with observations, we find that mixing ratio variations at the Middle cloud top can explain the observed variability of SO2 and H2O. The sulfur-water chemistry in the Middle Atmosphere is responsible for the H2O-SO2 anti-correlation at 64 km. Eddy transport change alone cannot explain the variations of both species. These results imply that variations of species abundance in the Middle Atmosphere are significantly influenced by the lower atmospheric processes. Continued ground-based measurements of the co-evolution of SO2 and H2O above the clouds and new spacecraft missions will be crucial for uncover the complicated processes underlying the interaction among the lower Atmosphere, the clouds and the Middle Atmosphere of Venus.
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revisiting the sulfur water chemical system in the Middle Atmosphere of venus
arXiv: Earth and Planetary Astrophysics, 2020Co-Authors: Wencheng D. Shao, Xi Zhang, Carver J. Bierson, Thérèse EncrenazAbstract:Sulfur-water chemistry plays an important role in the Middle Atmosphere of Venus. Ground based observations have found that simultaneously observed SO2 and H2O at ~64 km vary with time and are temporally anti-correlated. To understand these observations, we explore the sulfur-water chemical system using a one-dimensional chemistry-diffusion model. We find that SO2 and H2O mixing ratios above the clouds are highly dependent on mixing ratios of the two species at the Middle cloud top (58 km). The behavior of sulfur-water chemical system can be classified into three regimes but there is no abrupt transition among these regimes. In particular, there is no bifurcation behavior as previously claimed. We also find that the SO2 self-shielding effect causes H2O above the clouds to respond to the Middle cloud top in a non-monotonic fashion. Through comparison with observations, we find that mixing ratio variations at the Middle cloud top can explain the observed variability of SO2 and H2O. The sulfur-water chemistry in the Middle Atmosphere is responsible for the H2O-SO2 anti-correlation at 64 km. Eddy transport change alone cannot explain the variations of both species. These results imply that variations of species abundance in the Middle Atmosphere are significantly influenced by the lower atmospheric processes. Continued ground-based measurements of the co-evolution of SO2 and H2O above the clouds and new spacecraft missions will be crucial for uncover the complicated processes underlying the interaction among the lower Atmosphere, the clouds and the Middle Atmosphere of Venus.
Wencheng D. Shao - One of the best experts on this subject based on the ideXlab platform.
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Revisiting the Sulfur‐Water Chemical System in the Middle Atmosphere of Venus
Journal of Geophysical Research: Planets, 2020Co-Authors: Wencheng D. Shao, Xi Zhang, Carver J. Bierson, Thérèse EncrenazAbstract:Sulfur-water chemistry plays an important role in the Middle Atmosphere of Venus. Ground based observations have found that simultaneously observed SO2 and H2O at ~64 km vary with time and are temporally anti-correlated. To understand these observations, we explore the sulfur-water chemical system using a one-dimensional chemistry-diffusion model. We find that SO2 and H2O mixing ratios above the clouds are highly dependent on mixing ratios of the two species at the Middle cloud top (58 km). The behavior of sulfur-water chemical system can be classified into three regimes but there is no abrupt transition among these regimes. In particular, there is no bifurcation behavior as previously claimed. We also find that the SO2 self-shielding effect causes H2O above the clouds to respond to the Middle cloud top in a non-monotonic fashion. Through comparison with observations, we find that mixing ratio variations at the Middle cloud top can explain the observed variability of SO2 and H2O. The sulfur-water chemistry in the Middle Atmosphere is responsible for the H2O-SO2 anti-correlation at 64 km. Eddy transport change alone cannot explain the variations of both species. These results imply that variations of species abundance in the Middle Atmosphere are significantly influenced by the lower atmospheric processes. Continued ground-based measurements of the co-evolution of SO2 and H2O above the clouds and new spacecraft missions will be crucial for uncover the complicated processes underlying the interaction among the lower Atmosphere, the clouds and the Middle Atmosphere of Venus.
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revisiting the sulfur water chemical system in the Middle Atmosphere of venus
arXiv: Earth and Planetary Astrophysics, 2020Co-Authors: Wencheng D. Shao, Xi Zhang, Carver J. Bierson, Thérèse EncrenazAbstract:Sulfur-water chemistry plays an important role in the Middle Atmosphere of Venus. Ground based observations have found that simultaneously observed SO2 and H2O at ~64 km vary with time and are temporally anti-correlated. To understand these observations, we explore the sulfur-water chemical system using a one-dimensional chemistry-diffusion model. We find that SO2 and H2O mixing ratios above the clouds are highly dependent on mixing ratios of the two species at the Middle cloud top (58 km). The behavior of sulfur-water chemical system can be classified into three regimes but there is no abrupt transition among these regimes. In particular, there is no bifurcation behavior as previously claimed. We also find that the SO2 self-shielding effect causes H2O above the clouds to respond to the Middle cloud top in a non-monotonic fashion. Through comparison with observations, we find that mixing ratio variations at the Middle cloud top can explain the observed variability of SO2 and H2O. The sulfur-water chemistry in the Middle Atmosphere is responsible for the H2O-SO2 anti-correlation at 64 km. Eddy transport change alone cannot explain the variations of both species. These results imply that variations of species abundance in the Middle Atmosphere are significantly influenced by the lower atmospheric processes. Continued ground-based measurements of the co-evolution of SO2 and H2O above the clouds and new spacecraft missions will be crucial for uncover the complicated processes underlying the interaction among the lower Atmosphere, the clouds and the Middle Atmosphere of Venus.
Xi Zhang - One of the best experts on this subject based on the ideXlab platform.
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Revisiting the Sulfur‐Water Chemical System in the Middle Atmosphere of Venus
Journal of Geophysical Research: Planets, 2020Co-Authors: Wencheng D. Shao, Xi Zhang, Carver J. Bierson, Thérèse EncrenazAbstract:Sulfur-water chemistry plays an important role in the Middle Atmosphere of Venus. Ground based observations have found that simultaneously observed SO2 and H2O at ~64 km vary with time and are temporally anti-correlated. To understand these observations, we explore the sulfur-water chemical system using a one-dimensional chemistry-diffusion model. We find that SO2 and H2O mixing ratios above the clouds are highly dependent on mixing ratios of the two species at the Middle cloud top (58 km). The behavior of sulfur-water chemical system can be classified into three regimes but there is no abrupt transition among these regimes. In particular, there is no bifurcation behavior as previously claimed. We also find that the SO2 self-shielding effect causes H2O above the clouds to respond to the Middle cloud top in a non-monotonic fashion. Through comparison with observations, we find that mixing ratio variations at the Middle cloud top can explain the observed variability of SO2 and H2O. The sulfur-water chemistry in the Middle Atmosphere is responsible for the H2O-SO2 anti-correlation at 64 km. Eddy transport change alone cannot explain the variations of both species. These results imply that variations of species abundance in the Middle Atmosphere are significantly influenced by the lower atmospheric processes. Continued ground-based measurements of the co-evolution of SO2 and H2O above the clouds and new spacecraft missions will be crucial for uncover the complicated processes underlying the interaction among the lower Atmosphere, the clouds and the Middle Atmosphere of Venus.
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revisiting the sulfur water chemical system in the Middle Atmosphere of venus
arXiv: Earth and Planetary Astrophysics, 2020Co-Authors: Wencheng D. Shao, Xi Zhang, Carver J. Bierson, Thérèse EncrenazAbstract:Sulfur-water chemistry plays an important role in the Middle Atmosphere of Venus. Ground based observations have found that simultaneously observed SO2 and H2O at ~64 km vary with time and are temporally anti-correlated. To understand these observations, we explore the sulfur-water chemical system using a one-dimensional chemistry-diffusion model. We find that SO2 and H2O mixing ratios above the clouds are highly dependent on mixing ratios of the two species at the Middle cloud top (58 km). The behavior of sulfur-water chemical system can be classified into three regimes but there is no abrupt transition among these regimes. In particular, there is no bifurcation behavior as previously claimed. We also find that the SO2 self-shielding effect causes H2O above the clouds to respond to the Middle cloud top in a non-monotonic fashion. Through comparison with observations, we find that mixing ratio variations at the Middle cloud top can explain the observed variability of SO2 and H2O. The sulfur-water chemistry in the Middle Atmosphere is responsible for the H2O-SO2 anti-correlation at 64 km. Eddy transport change alone cannot explain the variations of both species. These results imply that variations of species abundance in the Middle Atmosphere are significantly influenced by the lower atmospheric processes. Continued ground-based measurements of the co-evolution of SO2 and H2O above the clouds and new spacecraft missions will be crucial for uncover the complicated processes underlying the interaction among the lower Atmosphere, the clouds and the Middle Atmosphere of Venus.
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Revisiting the Sulfur-Water Chemical System in the Middle Atmosphere of Venus
'American Geophysical Union (AGU)', 2020Co-Authors: Shao, Wencheng D., Xi Zhang, Bierson, Carver J., Encrenaz ThereseAbstract:Sulfur-water chemistry plays an important role in the Middle Atmosphere of Venus. Ground based observations have found that simultaneously observed SO2 and H2O at ~64 km vary with time and are temporally anti-correlated. To understand these observations, we explore the sulfur-water chemical system using a one-dimensional chemistry-diffusion model. We find that SO2 and H2O mixing ratios above the clouds are highly dependent on mixing ratios of the two species at the Middle cloud top (58 km). The behavior of sulfur-water chemical system can be classified into three regimes but there is no abrupt transition among these regimes. In particular, there is no bifurcation behavior as previously claimed. We also find that the SO2 self-shielding effect causes H2O above the clouds to respond to the Middle cloud top in a non-monotonic fashion. Through comparison with observations, we find that mixing ratio variations at the Middle cloud top can explain the observed variability of SO2 and H2O. The sulfur-water chemistry in the Middle Atmosphere is responsible for the H2O-SO2 anti-correlation at 64 km. Eddy transport change alone cannot explain the variations of both species. These results imply that variations of species abundance in the Middle Atmosphere are significantly influenced by the lower atmospheric processes. Continued ground-based measurements of the co-evolution of SO2 and H2O above the clouds and new spacecraft missions will be crucial for uncover the complicated processes underlying the interaction among the lower Atmosphere, the clouds and the Middle Atmosphere of Venus.Comment: 26 pages, 8 figures. The manuscript has been accepted by JGR-Planet
Theodore G. Shepherd - One of the best experts on this subject based on the ideXlab platform.
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Transport in the Middle Atmosphere
Journal of the Meteorological Society of Japan, 2007Co-Authors: Theodore G. ShepherdAbstract:An overview is provided of the current understanding of transport in the Middle Atmosphere. Over the past quarter century this subject has evolved from a basic recognition of the Brewer-Dobson circulation to a detailed appreciation of many key features of transport such as the stratospheric surf zone, mixing barriers, and the dynamics of filamentation. Whilst the elegant theoretical framework for Middle Atmosphere transport that emerged roughly twenty years ago never fulfilled its promise, useful phenomenological models have been developed together with innovative diagnostic methods. These advances were made possible by the advent of plentiful satellite and aircraft observations of long-lived chemical species together with developments in data assimilation and numerical modeling, and have been driven in large measure by the problem of stratospheric ozone depletion. This review is primarily focused on the stratosphere, where both the interest and the knowledge are the greatest, but a few remarks are also made on the mesosphere.
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Response of the Middle Atmosphere to CO2 Doubling: Results from the Canadian Middle Atmosphere Model
Journal of Climate, 2007Co-Authors: V. I. Fomichev, J. De Grandpré, S. R. Beagley, A. I. Jonsson, C. Mclandress, K. Semeniuk, Theodore G. ShepherdAbstract:Abstract The Canadian Middle Atmosphere Model (CMAM) has been used to examine the Middle Atmosphere response to CO2 doubling. The radiative-photochemical response induced by doubling CO2 alone and the response produced by changes in prescribed SSTs are found to be approximately additive, with the former effect dominating throughout the Middle Atmosphere. The paper discusses the overall response, with emphasis on the effects of SST changes, which allow a tropospheric response to the CO2 forcing. The overall response is a cooling of the Middle Atmosphere accompanied by significant increases in the ozone and water vapor abundances. The ozone radiative feedback occurs through both an increase in solar heating and a decrease in infrared cooling, with the latter accounting for up to 15% of the total effect. Changes in global mean water vapor cooling are negligible above ∼30 hPa. Near the polar summer mesopause, the temperature response is weak and not statistically significant. The main effects of SST changes a...
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Some challenges of Middle Atmosphere data assimilation
Quarterly Journal of the Royal Meteorological Society, 2005Co-Authors: S. Polavarapu, Theodore G. Shepherd, Yves Rochon, Shuzhan RenAbstract:The assimilation of measurements from the stratosphere and mesosphere is becoming increasingly common as the lids of weather prediction and climate models rise into the mesosphere and thermosphere. However, the dynamics of the Middle Atmosphere pose specific challenges to the assimilation of measurements from this region. Forecast-error variances can be very large in the mesosphere and this can render assimilation schemes very sensitive to the details of the specification of forecast error correlations. An example is shown where observations in the stratosphere are able to produce increments in the mesosphere. Such sensitivity of the assimilation scheme to misspecification of covariances can also amplify any existing biases in measurements or forecasts. Since both models and measurements of the Middle Atmosphere are known to have biases, the separation of these sources of bias remains a issue. Finally, well-known deficiencies of assimilation schemes, such as the production of imbalanced states or the assumption of zero bias, are proposed explanations for the inaccurate transport resulting from assimilated winds. The inability of assimilated winds to accurately transport constituents in the Middle Atmosphere remains a fundamental issue limiting the use of assimilated products for applications involving longer time-scales.
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The Middle Atmosphere
Journal of Atmospheric and Solar-Terrestrial Physics, 2000Co-Authors: Theodore G. ShepherdAbstract:Abstract The last 50 years have seen enormous advances in our knowledge and understanding of the stratosphere and mesosphere, which together comprise the Middle Atmosphere. Beginning from a phase of basic discovery, we have now reached the stage where most observed phenomena can be modelled from first principles with a reasonable degree of fidelity, and where there is an overall theoretical framework which can be tested against measurements and models. This review surveys a number of major surprises in Middle Atmosphere science over the past 50 years. A phenomenological and historical approach is adopted in each case, leading up to the current literature. Along the way, a common thread emerges: the central role of waves, of various types, in redistributing angular momentum within the Atmosphere, and the global nature of the atmospheric response to such redistribution.
Carver J. Bierson - One of the best experts on this subject based on the ideXlab platform.
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Revisiting the Sulfur‐Water Chemical System in the Middle Atmosphere of Venus
Journal of Geophysical Research: Planets, 2020Co-Authors: Wencheng D. Shao, Xi Zhang, Carver J. Bierson, Thérèse EncrenazAbstract:Sulfur-water chemistry plays an important role in the Middle Atmosphere of Venus. Ground based observations have found that simultaneously observed SO2 and H2O at ~64 km vary with time and are temporally anti-correlated. To understand these observations, we explore the sulfur-water chemical system using a one-dimensional chemistry-diffusion model. We find that SO2 and H2O mixing ratios above the clouds are highly dependent on mixing ratios of the two species at the Middle cloud top (58 km). The behavior of sulfur-water chemical system can be classified into three regimes but there is no abrupt transition among these regimes. In particular, there is no bifurcation behavior as previously claimed. We also find that the SO2 self-shielding effect causes H2O above the clouds to respond to the Middle cloud top in a non-monotonic fashion. Through comparison with observations, we find that mixing ratio variations at the Middle cloud top can explain the observed variability of SO2 and H2O. The sulfur-water chemistry in the Middle Atmosphere is responsible for the H2O-SO2 anti-correlation at 64 km. Eddy transport change alone cannot explain the variations of both species. These results imply that variations of species abundance in the Middle Atmosphere are significantly influenced by the lower atmospheric processes. Continued ground-based measurements of the co-evolution of SO2 and H2O above the clouds and new spacecraft missions will be crucial for uncover the complicated processes underlying the interaction among the lower Atmosphere, the clouds and the Middle Atmosphere of Venus.
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revisiting the sulfur water chemical system in the Middle Atmosphere of venus
arXiv: Earth and Planetary Astrophysics, 2020Co-Authors: Wencheng D. Shao, Xi Zhang, Carver J. Bierson, Thérèse EncrenazAbstract:Sulfur-water chemistry plays an important role in the Middle Atmosphere of Venus. Ground based observations have found that simultaneously observed SO2 and H2O at ~64 km vary with time and are temporally anti-correlated. To understand these observations, we explore the sulfur-water chemical system using a one-dimensional chemistry-diffusion model. We find that SO2 and H2O mixing ratios above the clouds are highly dependent on mixing ratios of the two species at the Middle cloud top (58 km). The behavior of sulfur-water chemical system can be classified into three regimes but there is no abrupt transition among these regimes. In particular, there is no bifurcation behavior as previously claimed. We also find that the SO2 self-shielding effect causes H2O above the clouds to respond to the Middle cloud top in a non-monotonic fashion. Through comparison with observations, we find that mixing ratio variations at the Middle cloud top can explain the observed variability of SO2 and H2O. The sulfur-water chemistry in the Middle Atmosphere is responsible for the H2O-SO2 anti-correlation at 64 km. Eddy transport change alone cannot explain the variations of both species. These results imply that variations of species abundance in the Middle Atmosphere are significantly influenced by the lower atmospheric processes. Continued ground-based measurements of the co-evolution of SO2 and H2O above the clouds and new spacecraft missions will be crucial for uncover the complicated processes underlying the interaction among the lower Atmosphere, the clouds and the Middle Atmosphere of Venus.