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A. Waibel - One of the best experts on this subject based on the ideXlab platform.
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In Situ Trace Gas and Particle Measurements in the Summer Lower Stratosphere during STREAM II: Implications for O_3 Production
Journal of Atmospheric Chemistry, 1997Co-Authors: A. Bregman, F. Arnold, V. Bürger, H. Fisher, J. Lelieveld, B. A. Scheeren, J. Schneider, P. C. Siegmund, J. Ström, A. WaibelAbstract:In situ aircraft measurements of O_3, CO,HNO_3, and aerosol particles are presented,performed over the North Sea region in the summerlower Stratosphere during the STREAM II campaign(Stratosphere Troposphere Experiments by AircraftMeasurements) in July 1994. Occasionally, high COconcentrations of 200-300 pbbv were measured in thelowermost Stratosphere, together with relatively highHNO_3 concentrations up to 1.6 ppbv. The particlenumber concentration (at standard pressure andtemperature) between 0.018-1 μm decreased acrossthe tropopause, from >1000 cm^-3 in the uppertroposphere to
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In Situ Trace Gas and Particle Measurements in the Summer Lower Stratosphere during STREAM II: Implications for O_3 Production
Journal of Atmospheric Chemistry, 1997Co-Authors: A. Bregman, F. Arnold, V. Bürger, H. Fisher, J. Lelieveld, B. A. Scheeren, J. Schneider, P. C. Siegmund, J. Ström, A. WaibelAbstract:In situ aircraft measurements of O_3, CO,HNO_3, and aerosol particles are presented,performed over the North Sea region in the summerlower Stratosphere during the STREAM II campaign(Stratosphere Troposphere Experiments by AircraftMeasurements) in July 1994. Occasionally, high COconcentrations of 200-300 pbbv were measured in thelowermost Stratosphere, together with relatively highHNO_3 concentrations up to 1.6 ppbv. The particlenumber concentration (at standard pressure andtemperature) between 0.018-1 μm decreased acrossthe tropopause, from >1000 cm^-3 in the uppertroposphere to
Gilda E. Ballester - One of the best experts on this subject based on the ideXlab platform.
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An ultrahot gas-giant exoplanet with a Stratosphere
Nature, 2017Co-Authors: Thomas M. Evans, David K. Sing, Tiffany Kataria, Jayesh Goyal, Nikolay Nikolov, Hannah R. Wakeford, Drake Deming, Mark S. Marley, David S. Amundsen, Gilda E. BallesterAbstract:Observations of the gas-giant exoplanet WASP-121b reveal near-infrared emission lines of water, suggesting that the planet has a Stratosphere—a layer in the upper atmosphere where temperature increases with altitude. Infrared radiation emitted from a planet contains information about the chemical composition and vertical temperature profile of its atmosphere^ 1 , 2 , 3 . If upper layers are cooler than lower layers, molecular gases will produce absorption features in the planetary thermal spectrum^ 4 , 5 . Conversely, if there is a Stratosphere—where temperature increases with altitude—these molecular features will be observed in emission^ 6 , 7 , 8 . It has been suggested that Stratospheres could form in highly irradiated exoplanets^ 9 , 10 , but the extent to which this occurs is unresolved both theoretically^ 11 , 12 and observationally^ 3 , 13 , 14 , 15 . A previous claim for the presence of a Stratosphere^ 14 remains open to question, owing to the challenges posed by the highly variable host star and the low spectral resolution of the measurements^ 3 . Here we report a near-infrared thermal spectrum for the ultrahot gas giant WASP-121b, which has an equilibrium temperature of approximately 2,500 kelvin. Water is resolved in emission, providing a detection of an exoplanet Stratosphere at 5 σ confidence. These observations imply that a substantial fraction of incident stellar radiation is retained at high altitudes in the atmosphere, possibly by absorbing chemical species such as gaseous vanadium oxide and titanium oxide. Earth's atmosphere consists of layers that are partially defined by their temperature. In the troposphere, which is just above the Earth's surface, temperature decreases with altitude, whereas the layer above, the Stratosphere, is warmer. Exoplanets could also have Stratospheres, but whether they actually do has been an open question. One way to find out is to observe whether molecular species are seen in emission in the planet's thermal spectrum, which would indicate that the overlying layer is hotter than the lower one. Tom Evans et al . report observations of the gas-giant exoplanet WASP-121b, which reveal emission lines of water, from which they conclude that the planet has a Stratosphere.
Leonhard Pfister - One of the best experts on this subject based on the ideXlab platform.
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Stratosphere troposphere exchange
Reviews of Geophysics, 1995Co-Authors: James R Holton, Anne R. Douglass, Richard B Rood, Michael E Mcintyre, P H Haynes, Leonhard PfisterAbstract:In the past, studies of Stratosphere-troposphere exchange of mass and chemical species have mainly emphasized the synoptic- and small-scale mechanisms of exchange. This review, however, includes also the global-scale aspects of exchange, such as the transport across an isentropic surface (potential temperature about 380 K) that in the tropics lies just above the tropopause, near the 100-hPa pressure level. Such a surface divides the Stratosphere into an “overworld” and an extratropical “lowermost Stratosphere” that for transport purposes need to be sharply distinguished. This approach places Stratosphere-troposphere exchange in the framework of the general circulation and helps to clarify the roles of the different mechanisms involved and the interplay between large and small scales. The role of waves and eddies in the extratropical overworld is emphasized. There, wave-induced forces drive a kind of global-scale extratropical “fluid-dynamical suction pump,” which withdraws air upward and poleward from the tropical lower Stratosphere and pushes it poleward and downward into the extratropical troposphere. The resulting global-scale circulation drives the Stratosphere away from radiative equilibrium conditions. Wave-induced forces may be considered to exert a nonlocal control, mainly downward in the extratropics but reaching laterally into the tropics, over the transport of mass across lower stratospheric isentropic surfaces. This mass transport is for many purposes a useful measure of global-scale Stratosphere-troposphere exchange, especially on seasonal or longer timescales. Because the strongest wave-induced forces occur in the northern hemisphere winter season, the exchange rate is also a maximum at that season. The global exchange rate is not determined by details of near-tropopause phenomena such as penetrative cumulus convection or small-scale mixing associated with upper level fronts and cyclones. These smaller-scale processes must be considered, however, in order to understand the finer details of exchange. Moist convection appears to play an important role in the tropics in accounting for the extreme dehydration of air entering the Stratosphere. Stratospheric air finds its way back into the troposphere through a vast variety of irreversible eddy exchange phenomena, including tropopause folding and the formation of so-called tropical upper tropospheric troughs and consequent irreversible exchange. General circulation models are able to simulate the mean global-scale mass exchange and its seasonal cycle but are not able to properly resolve the tropical dehydration process. Two-dimensional (height-latitude) models commonly used for assessment of human impact on the ozone layer include representation of Stratosphere-troposphere exchange that is adequate to allow reasonable simulation of photochemical processes occurring in the overworld. However, for assessing changes in the lowermost Stratosphere, the strong longitudinal asymmetries in Stratosphere-troposphere exchange render current two-dimensional models inadequate. Either current transport parameterizations must be improved, or else, more likely, such changes can be adequately assessed only by three-dimensional models.
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Stratosphere‐troposphere exchange
Reviews of Geophysics, 1995Co-Authors: James R Holton, Anne R. Douglass, Richard B Rood, Michael E Mcintyre, P H Haynes, Leonhard PfisterAbstract:In the past, studies of Stratosphere-troposphere exchange of mass and chemical species have mainly emphasized the synoptic- and small-scale mechanisms of exchange. This review, however, includes also the global-scale aspects of exchange, such as the transport across an isentropic surface (potential temperature about 380 K) that in the tropics lies just above the tropopause, near the 100-hPa pressure level. Such a surface divides the Stratosphere into an “overworld” and an extratropical “lowermost Stratosphere” that for transport purposes need to be sharply distinguished. This approach places Stratosphere-troposphere exchange in the framework of the general circulation and helps to clarify the roles of the different mechanisms involved and the interplay between large and small scales. The role of waves and eddies in the extratropical overworld is emphasized. There, wave-induced forces drive a kind of global-scale extratropical “fluid-dynamical suction pump,” which withdraws air upward and poleward from the tropical lower Stratosphere and pushes it poleward and downward into the extratropical troposphere. The resulting global-scale circulation drives the Stratosphere away from radiative equilibrium conditions. Wave-induced forces may be considered to exert a nonlocal control, mainly downward in the extratropics but reaching laterally into the tropics, over the transport of mass across lower stratospheric isentropic surfaces. This mass transport is for many purposes a useful measure of global-scale Stratosphere-troposphere exchange, especially on seasonal or longer timescales. Because the strongest wave-induced forces occur in the northern hemisphere winter season, the exchange rate is also a maximum at that season. The global exchange rate is not determined by details of near-tropopause phenomena such as penetrative cumulus convection or small-scale mixing associated with upper level fronts and cyclones. These smaller-scale processes must be considered, however, in order to understand the finer details of exchange. Moist convection appears to play an important role in the tropics in accounting for the extreme dehydration of air entering the Stratosphere. Stratospheric air finds its way back into the troposphere through a vast variety of irreversible eddy exchange phenomena, including tropopause folding and the formation of so-called tropical upper tropospheric troughs and consequent irreversible exchange. General circulation models are able to simulate the mean global-scale mass exchange and its seasonal cycle but are not able to properly resolve the tropical dehydration process. Two-dimensional (height-latitude) models commonly used for assessment of human impact on the ozone layer include representation of Stratosphere-troposphere exchange that is adequate to allow reasonable simulation of photochemical processes occurring in the overworld. However, for assessing changes in the lowermost Stratosphere, the strong longitudinal asymmetries in Stratosphere-troposphere exchange render current two-dimensional models inadequate. Either current transport parameterizations must be improved, or else, more likely, such changes can be adequately assessed only by three-dimensional models.
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Stratosphere‐troposphere exchange
Reviews of Geophysics, 1995Co-Authors: James R Holton, Anne R. Douglass, Richard B Rood, Michael E Mcintyre, P H Haynes, Leonhard PfisterAbstract:In the past, studies of Stratosphere-troposphere exchange of mass and chemical species have mainly emphasized the synoptic- and small-scale mechanisms of exchange. This review, however, includes also the global-scale aspects of exchange, such as the transport across an isentropic surface (potential temperature about 380 K) that in the tropics lies just above the tropopause, near the 100-hPa pressure level. Such a surface divides the Stratosphere into an “overworld” and an extratropical “lowermost Stratosphere” that for transport purposes need to be sharply distinguished. This approach places Stratosphere-troposphere exchange in the framework of the general circulation and helps to clarify the roles of the different mechanisms involved and the interplay between large and small scales. The role of waves and eddies in the extratropical overworld is emphasized. There, wave-induced forces drive a kind of global-scale extratropical “fluid-dynamical suction pump,” which withdraws air upward and poleward from the tropical lower Stratosphere and pushes it poleward and downward into the extratropical troposphere. The resulting global-scale circulation drives the Stratosphere away from radiative equilibrium conditions. Wave-induced forces may be considered to exert a nonlocal control, mainly downward in the extratropics but reaching laterally into the tropics, over the transport of mass across lower stratospheric isentropic surfaces. This mass transport is for many purposes a useful measure of global-scale Stratosphere-troposphere exchange, especially on seasonal or longer timescales. Because the strongest wave-induced forces occur in the northern hemisphere winter season, the exchange rate is also a maximum at that season. The global exchange rate is not determined by details of near-tropopause phenomena such as penetrative cumulus convection or small-scale mixing associated with upper level fronts and cyclones. These smaller-scale processes must be considered, however, in order to understand the finer details of exchange. Moist convection appears to play an important role in the tropics in accounting for the extreme dehydration of air entering the Stratosphere. Stratospheric air finds its way back into the troposphere through a vast variety of irreversible eddy exchange phenomena, including tropopause folding and the formation of so-called tropical upper tropospheric troughs and consequent irreversible exchange. General circulation models are able to simulate the mean global-scale mass exchange and its seasonal cycle but are not able to properly resolve the tropical dehydration process. Two-dimensional (height-latitude) models commonly used for assessment of human impact on the ozone layer include representation of Stratosphere-troposphere exchange that is adequate to allow reasonable simulation of photochemical processes occurring in the overworld. However, for assessing changes in the lowermost Stratosphere, the strong longitudinal asymmetries in Stratosphere-troposphere exchange render current two-dimensional models inadequate. Either current transport parameterizations must be improved, or else, more likely, such changes can be adequately assessed only by three-dimensional models.
Drake Deming - One of the best experts on this subject based on the ideXlab platform.
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An ultrahot gas-giant exoplanet with a Stratosphere
Nature, 2017Co-Authors: Thomas M. Evans, David K. Sing, Tiffany Kataria, Jayesh Goyal, Nikolay Nikolov, Hannah R. Wakeford, Drake Deming, Mark S. Marley, David S. Amundsen, Gilda E. BallesterAbstract:Observations of the gas-giant exoplanet WASP-121b reveal near-infrared emission lines of water, suggesting that the planet has a Stratosphere—a layer in the upper atmosphere where temperature increases with altitude. Infrared radiation emitted from a planet contains information about the chemical composition and vertical temperature profile of its atmosphere^ 1 , 2 , 3 . If upper layers are cooler than lower layers, molecular gases will produce absorption features in the planetary thermal spectrum^ 4 , 5 . Conversely, if there is a Stratosphere—where temperature increases with altitude—these molecular features will be observed in emission^ 6 , 7 , 8 . It has been suggested that Stratospheres could form in highly irradiated exoplanets^ 9 , 10 , but the extent to which this occurs is unresolved both theoretically^ 11 , 12 and observationally^ 3 , 13 , 14 , 15 . A previous claim for the presence of a Stratosphere^ 14 remains open to question, owing to the challenges posed by the highly variable host star and the low spectral resolution of the measurements^ 3 . Here we report a near-infrared thermal spectrum for the ultrahot gas giant WASP-121b, which has an equilibrium temperature of approximately 2,500 kelvin. Water is resolved in emission, providing a detection of an exoplanet Stratosphere at 5 σ confidence. These observations imply that a substantial fraction of incident stellar radiation is retained at high altitudes in the atmosphere, possibly by absorbing chemical species such as gaseous vanadium oxide and titanium oxide. Earth's atmosphere consists of layers that are partially defined by their temperature. In the troposphere, which is just above the Earth's surface, temperature decreases with altitude, whereas the layer above, the Stratosphere, is warmer. Exoplanets could also have Stratospheres, but whether they actually do has been an open question. One way to find out is to observe whether molecular species are seen in emission in the planet's thermal spectrum, which would indicate that the overlying layer is hotter than the lower one. Tom Evans et al . report observations of the gas-giant exoplanet WASP-121b, which reveal emission lines of water, from which they conclude that the planet has a Stratosphere.
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An ultrahot gas-giant exoplanet with a Stratosphere
Nature, 2017Co-Authors: Thomas Evans, Tiffany Kataria, Jayesh Goyal, Nikolay Nikolov, Hannah R. Wakeford, Drake Deming, David Sing, Mark Marley, David Amundsen, Gilda BallesterAbstract:Infrared radiation emitted from a planet contains information about the chemical composition and vertical temperature profile of its atmosphere1,2,3. If upper layers are cooler than lower layers, molecular gases will produce absorption features in the planetary thermal spectrum4,5. Conversely, if there is a Stratosphere—where temperature increases with altitude—these molecular features will be observed in emission6,7,8. It has been suggested that Stratospheres could form in highly irradiated exoplanets9,10, but the extent to which this occurs is unresolved both theoretically11,12 and observationally3,13,14,15. A previous claim for the presence of a Stratosphere14 remains open to question, owing to the challenges posed by the highly variable host star and the low spectral resolution of the measurements3. Here we report a near-infrared thermal spectrum for the ultrahot gas giant WASP-121b, which has an equilibrium temperature of approximately 2,500 kelvin. Water is resolved in emission, providing a detection of an exoplanet Stratosphere at 5σ confidence. These observations imply that a substantial fraction of incident stellar radiation is retained at high altitudes in the atmosphere, possibly by absorbing chemical species such as gaseous vanadium oxide and titanium oxide.
Hannah R. Wakeford - One of the best experts on this subject based on the ideXlab platform.
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An ultrahot gas-giant exoplanet with a Stratosphere
Nature, 2017Co-Authors: Thomas M. Evans, David K. Sing, Tiffany Kataria, Jayesh Goyal, Nikolay Nikolov, Hannah R. Wakeford, Drake Deming, Mark S. Marley, David S. Amundsen, Gilda E. BallesterAbstract:Observations of the gas-giant exoplanet WASP-121b reveal near-infrared emission lines of water, suggesting that the planet has a Stratosphere—a layer in the upper atmosphere where temperature increases with altitude. Infrared radiation emitted from a planet contains information about the chemical composition and vertical temperature profile of its atmosphere^ 1 , 2 , 3 . If upper layers are cooler than lower layers, molecular gases will produce absorption features in the planetary thermal spectrum^ 4 , 5 . Conversely, if there is a Stratosphere—where temperature increases with altitude—these molecular features will be observed in emission^ 6 , 7 , 8 . It has been suggested that Stratospheres could form in highly irradiated exoplanets^ 9 , 10 , but the extent to which this occurs is unresolved both theoretically^ 11 , 12 and observationally^ 3 , 13 , 14 , 15 . A previous claim for the presence of a Stratosphere^ 14 remains open to question, owing to the challenges posed by the highly variable host star and the low spectral resolution of the measurements^ 3 . Here we report a near-infrared thermal spectrum for the ultrahot gas giant WASP-121b, which has an equilibrium temperature of approximately 2,500 kelvin. Water is resolved in emission, providing a detection of an exoplanet Stratosphere at 5 σ confidence. These observations imply that a substantial fraction of incident stellar radiation is retained at high altitudes in the atmosphere, possibly by absorbing chemical species such as gaseous vanadium oxide and titanium oxide. Earth's atmosphere consists of layers that are partially defined by their temperature. In the troposphere, which is just above the Earth's surface, temperature decreases with altitude, whereas the layer above, the Stratosphere, is warmer. Exoplanets could also have Stratospheres, but whether they actually do has been an open question. One way to find out is to observe whether molecular species are seen in emission in the planet's thermal spectrum, which would indicate that the overlying layer is hotter than the lower one. Tom Evans et al . report observations of the gas-giant exoplanet WASP-121b, which reveal emission lines of water, from which they conclude that the planet has a Stratosphere.
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An ultrahot gas-giant exoplanet with a Stratosphere
Nature, 2017Co-Authors: Thomas Evans, Tiffany Kataria, Jayesh Goyal, Nikolay Nikolov, Hannah R. Wakeford, Drake Deming, David Sing, Mark Marley, David Amundsen, Gilda BallesterAbstract:Infrared radiation emitted from a planet contains information about the chemical composition and vertical temperature profile of its atmosphere1,2,3. If upper layers are cooler than lower layers, molecular gases will produce absorption features in the planetary thermal spectrum4,5. Conversely, if there is a Stratosphere—where temperature increases with altitude—these molecular features will be observed in emission6,7,8. It has been suggested that Stratospheres could form in highly irradiated exoplanets9,10, but the extent to which this occurs is unresolved both theoretically11,12 and observationally3,13,14,15. A previous claim for the presence of a Stratosphere14 remains open to question, owing to the challenges posed by the highly variable host star and the low spectral resolution of the measurements3. Here we report a near-infrared thermal spectrum for the ultrahot gas giant WASP-121b, which has an equilibrium temperature of approximately 2,500 kelvin. Water is resolved in emission, providing a detection of an exoplanet Stratosphere at 5σ confidence. These observations imply that a substantial fraction of incident stellar radiation is retained at high altitudes in the atmosphere, possibly by absorbing chemical species such as gaseous vanadium oxide and titanium oxide.
