The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
V. Grewe - One of the best experts on this subject based on the ideXlab platform.
-
Simulation of stratospheric Water Vapor trends: impact on stratospheric ozone chemistry
Atmospheric Chemistry and Physics, 2005Co-Authors: A. Stenke, V. GreweAbstract:A transient model simulation of the 40-year time period 1960 to 1999 with the coupled climate-chemistry model (CCM) ECHAM4.L39(DLR)/CHEM shows a stratospheric Water Vapor increase over the last two decades of 0.7 ppmv and, additionally, a short-term increase after major volcanic eruptions. Furthermore, a long-term decrease in global total ozone as well as a short-term ozone decline in the tropics after volcanic eruptions are modeled. In order to understand the resulting effects of the Water Vapor changes on lower stratospheric ozone chemistry, different perturbation simulations were performed with the CCM ECHAM4.L39(DLR)/CHEM feeding the Water Vapor perturbations only to the chemistry part. Two different long-term perturbations of lower stratospheric Water Vapor, +1 ppmv and +5 ppmv, and a short-term perturbation of +2 ppmv with an e-folding time of two months were applied. An additional stratospheric Water Vapor amount of 1 ppmv results in a 5?10% OH increase in the tropical lower stratosphere between 100 and 30 hPa. As a direct consequence of the OH increase the ozone destruction by the HOx cycle becomes 6.4% more effective. Coupling processes between the HOx-family and the NOx/ClOx-family also affect the ozone destruction by other catalytic reaction cycles. The NOx cycle becomes 1.6% less effective, whereas the effectiveness of the ClOx cycle is again slightly enhanced. A long-term Water Vapor increase does not only affect gas-phase chemistry, but also heterogeneous ozone chemistry in polar regions. The model results indicate an enhanced heterogeneous ozone depletion during antarctic spring due to a longer PSC existence period. In contrast, PSC formation in the northern hemisphere polar vortex and therefore heterogeneous ozone depletion during arctic spring are not affected by the Water Vapor increase, because of the less PSC activity. Finally, this study shows that 10% of the global total ozone decline in the transient model run can be explained by the modeled Water Vapor increase, but the simulated tropical ozone decrease after volcanic eruptions is caused dynamically rather than chemically.
-
Simulation of stratospheric Water Vapor trends: impact on stratospheric ozone chemistry
Atmospheric Chemistry and Physics Discussions, 2004Co-Authors: A. Stenke, V. GreweAbstract:A transient model simulation from 1960 to 2000 with the coupled climate-chemistry model (CCM) shows a stratospheric Water Vapor trend during the last two decades of +0.7 ppmv and additionally a short-term increase during volcanic eruptions. At the same time this model simulation shows a long-term decrease in total ozone and a short-term tropical ozone decline after a volcanic eruption. In order to understand the resulting effects of the Water Vapor changes on stratospheric ozone chemistry, different perturbation simulations have been performed with the CCM with the Water Vapor perturbations fed only to the chemistry part. Two different long-term perturbations of stratospheric Water Vapor, +1 ppmv and +5 ppmv, and a short-term perturbation of +2 ppmv with an e-folding time of two months have been simulated. Since Water Vapor acts as an in-situ source of odd hydrogen in the stratosphere, the Water Vapor perturbations affect the gas-phase chemistry of hydrogen oxides. An additional Water Vapor amount of +1 ppmv results in a 5?10% increase. Coupling processes between and / also affect the ozone destruction by other catalytic reaction cycles. The cycle becomes 6.4% more effective, whereas the cycle is 1.6% less effective. A long-term Water Vapor increase does not only affect the gas-phase chemistry, but also the heterogeneous ozone chemistry in polar regions. The additional Water Vapor intensifies the strong denitrification of the Antarctic winter stratosphere caused by an enhanced formation of polar stratospheric clouds. Thus it further facilitates the catalytic ozone removal by the cycle. The reduction of total column ozone during Antarctic spring peaks at ?3%. In contrast, heterogeneous chemistry during Arctic winter is not affected by the Water Vapor increase. The short-term perturbation studies show similar patterns, but because of the short perturbation time, the chemical effect on ozone is almost negligible. Finally, this study shows that 10% of the simulated long-term ozone decline in the transient model simulation can be explained by the Water Vapor increase, but the simulated tropical ozone decrease after volcanic eruptions is caused dynamically rather than chemically.
A. Stenke - One of the best experts on this subject based on the ideXlab platform.
-
Simulation of stratospheric Water Vapor trends: impact on stratospheric ozone chemistry
Atmospheric Chemistry and Physics, 2005Co-Authors: A. Stenke, V. GreweAbstract:A transient model simulation of the 40-year time period 1960 to 1999 with the coupled climate-chemistry model (CCM) ECHAM4.L39(DLR)/CHEM shows a stratospheric Water Vapor increase over the last two decades of 0.7 ppmv and, additionally, a short-term increase after major volcanic eruptions. Furthermore, a long-term decrease in global total ozone as well as a short-term ozone decline in the tropics after volcanic eruptions are modeled. In order to understand the resulting effects of the Water Vapor changes on lower stratospheric ozone chemistry, different perturbation simulations were performed with the CCM ECHAM4.L39(DLR)/CHEM feeding the Water Vapor perturbations only to the chemistry part. Two different long-term perturbations of lower stratospheric Water Vapor, +1 ppmv and +5 ppmv, and a short-term perturbation of +2 ppmv with an e-folding time of two months were applied. An additional stratospheric Water Vapor amount of 1 ppmv results in a 5?10% OH increase in the tropical lower stratosphere between 100 and 30 hPa. As a direct consequence of the OH increase the ozone destruction by the HOx cycle becomes 6.4% more effective. Coupling processes between the HOx-family and the NOx/ClOx-family also affect the ozone destruction by other catalytic reaction cycles. The NOx cycle becomes 1.6% less effective, whereas the effectiveness of the ClOx cycle is again slightly enhanced. A long-term Water Vapor increase does not only affect gas-phase chemistry, but also heterogeneous ozone chemistry in polar regions. The model results indicate an enhanced heterogeneous ozone depletion during antarctic spring due to a longer PSC existence period. In contrast, PSC formation in the northern hemisphere polar vortex and therefore heterogeneous ozone depletion during arctic spring are not affected by the Water Vapor increase, because of the less PSC activity. Finally, this study shows that 10% of the global total ozone decline in the transient model run can be explained by the modeled Water Vapor increase, but the simulated tropical ozone decrease after volcanic eruptions is caused dynamically rather than chemically.
-
Simulation of stratospheric Water Vapor trends: impact on stratospheric ozone chemistry
Atmospheric Chemistry and Physics Discussions, 2004Co-Authors: A. Stenke, V. GreweAbstract:A transient model simulation from 1960 to 2000 with the coupled climate-chemistry model (CCM) shows a stratospheric Water Vapor trend during the last two decades of +0.7 ppmv and additionally a short-term increase during volcanic eruptions. At the same time this model simulation shows a long-term decrease in total ozone and a short-term tropical ozone decline after a volcanic eruption. In order to understand the resulting effects of the Water Vapor changes on stratospheric ozone chemistry, different perturbation simulations have been performed with the CCM with the Water Vapor perturbations fed only to the chemistry part. Two different long-term perturbations of stratospheric Water Vapor, +1 ppmv and +5 ppmv, and a short-term perturbation of +2 ppmv with an e-folding time of two months have been simulated. Since Water Vapor acts as an in-situ source of odd hydrogen in the stratosphere, the Water Vapor perturbations affect the gas-phase chemistry of hydrogen oxides. An additional Water Vapor amount of +1 ppmv results in a 5?10% increase. Coupling processes between and / also affect the ozone destruction by other catalytic reaction cycles. The cycle becomes 6.4% more effective, whereas the cycle is 1.6% less effective. A long-term Water Vapor increase does not only affect the gas-phase chemistry, but also the heterogeneous ozone chemistry in polar regions. The additional Water Vapor intensifies the strong denitrification of the Antarctic winter stratosphere caused by an enhanced formation of polar stratospheric clouds. Thus it further facilitates the catalytic ozone removal by the cycle. The reduction of total column ozone during Antarctic spring peaks at ?3%. In contrast, heterogeneous chemistry during Arctic winter is not affected by the Water Vapor increase. The short-term perturbation studies show similar patterns, but because of the short perturbation time, the chemical effect on ozone is almost negligible. Finally, this study shows that 10% of the simulated long-term ozone decline in the transient model simulation can be explained by the Water Vapor increase, but the simulated tropical ozone decrease after volcanic eruptions is caused dynamically rather than chemically.
Matthias Wessling - One of the best experts on this subject based on the ideXlab platform.
-
mixed Water Vapor gas transport through the rubbery polymer pebax 1074
Journal of Membrane Science, 2009Co-Authors: Jens Potreck, D Kitty C Nijmeijer, Thomas Kosinski, Matthias WesslingAbstract:This work investigates the transport behavior of a hydrophilic, highly permeable type of poly ethylene oxide (PEO)-based block copolymer (PEBAX® 1074) as membrane material for the removal of Water Vapor from light gases. Water Vapor sorption isotherms in PEBAX® 1074 represent Flory–Huggins type of sorption and the highly hydrophilic nature of the block copolymer results in high amounts of absorbed Water (up to 0.4 g of Water per gram of dry polymer at 20 °C). When taking into account the swelling of the polymer due to Water Vapor sorption, the Fickian diffusion coefficient increases over the full activity range and changes over two orders of magnitude. As determined from measurements with binary gas mixtures, the Water Vapor permeability increases exponentially with increasing Water Vapor activity whereas the nitrogen permeability slightly decreases with increasing Water Vapor activity. Consequently, the Water over nitrogen selectivity increases with increasing Water Vapor activity. The results not only show the high potential of hydrophilic PEO-based block copolymers for dehydration purposes (e.g. the dehydration of flue gases, natural gas dew pointing or the humidification of air). Because of the high interaction of CO2 with the polar ether linkages in PEO-based block copolymers, these polymers also offer attractive routes to the integration of dehydration and CO2 capture using membrane technology.
-
Mixed Water Vapor/gas transport through the rubbery polymer PEBAX® 1074
Journal of Membrane Science, 2009Co-Authors: Jens Potreck, Thomas Kosinski, Dc Kitty Nijmeijer, Matthias WesslingAbstract:This work investigates the transport behavior of a hydrophilic, highly permeable type of poly ethylene oxide (PEO)-based block copolymer (PEBAX® 1074) as membrane material for the removal of Water Vapor from light gases. Water Vapor sorption isotherms in PEBAX® 1074 represent Flory–Huggins type of sorption and the highly hydrophilic nature of the block copolymer results in high amounts of absorbed Water (up to 0.4 g of Water per gram of dry polymer at 20 °C). When taking into account the swelling of the polymer due to Water Vapor sorption, the Fickian diffusion coefficient increases over the full activity range and changes over two orders of magnitude. As determined from measurements with binary gas mixtures, the Water Vapor permeability increases exponentially with increasing Water Vapor activity whereas the nitrogen permeability slightly decreases with increasing Water Vapor activity. Consequently, the Water over nitrogen selectivity increases with increasing Water Vapor activity. The results not only show the high potential of hydrophilic PEO-based block copolymers for dehydration purposes (e.g. the dehydration of flue gases, natural gas dew pointing or the humidification of air). Because of the high interaction of CO2 with the polar ether linkages in PEO-based block copolymers, these polymers also offer attractive routes to the integration of dehydration and CO2 capture using membrane technology.
J W Waters - One of the best experts on this subject based on the ideXlab platform.
-
baroclinic wave variations observed in mls upper tropospheric Water Vapor
Geophysical Research Letters, 1996Co-Authors: Elizabeth M Stone, William J Randel, John L Stanford, W G Read, J W WatersAbstract:Upper tropospheric Water Vapor measurements from the UARS Microwave Limb Sounder are used to investigate the structure and evolution of eastward traveling medium-scale wave features in Southern Hemisphere summertime. The extratropical Southern Hemisphere summer circulation pattern is frequently dominated by medium scale waves which exhibit life cycles of baroclinic growth and barotropic decay. The Water Vapor field during such life cycles is examined here and found to be well correlated with meteorological fields derived from European Centre for Medium Range Weather Forecasts global analyses. From mid January to mid February 1992 several episodes of growth and decay in the amplitude of eastward traveling waves are found in the Water Vapor and meteorological data at levels of the upper troposphere, with zonal waves four, five and six being predominant modes. The Water Vapor data are compared with derived potential vorticity (PV) fields, with strong anticorrelation observed in middle and high latitudes. The results are consistent with model paradigms for the structure and evolution of baroclinic disturbances, coupled with the known characteristics of high PV and low Water Vapor mixing ratios in lower stratospheric air parcels and the reverse for upper tropospheric air.
-
baroclinic wave variations observed in mls upper tropospheric Water Vapor
Geophysical Research Letters, 1996Co-Authors: Elizabeth M Stone, William J Randel, John L Stanford, W G Read, J W WatersAbstract:Upper tropospheric Water Vapor measurements from the UARS Microwave Limb Sounder are used to investigate the structure and evolution of eastward traveling medium-scale wave features in Southern Hemisphere summertime. The extratropical Southern Hemisphere summer circulation pattern is frequently dominated by medium scale waves which exhibit life cycles of baroclinic growth and barotropic decay. The Water Vapor field during such life cycles is examined here and found to be well correlated with meteorological fields derived from European Centre for Medium Range Weather Forecasts global analyses. From mid January to mid February 1992 several episodes of growth and decay in the amplitude of eastward traveling waves are found in the Water Vapor and meteorological data at levels of the upper troposphere, with zonal waves four, five and six being predominant modes. The Water Vapor data are compared with derived potential vorticity (PV) fields, with strong anticorrelation observed in middle and high latitudes. The results are consistent with model paradigms for the structure and evolution of baroclinic disturbances, coupled with the known characteristics of high PV and low Water Vapor mixing ratios in lower stratospheric air parcels and the reverse for upper tropospheric air.
M. T. K. Ling - One of the best experts on this subject based on the ideXlab platform.
-
Kinetics of Water Vapor diffusion in resins
Journal of Thermal Analysis and Calorimetry, 2016Co-Authors: V. V. Krongauz, S. E. Bennett, M. T. K. LingAbstract:The Water Vapor sorption and desorption kinetics were monitored in methyl methacrylate–acrylonitrile–butadiene–styrene copolymer (MABS), bromobutyl, ethylene–propylene–butadiene monomer (EPDM) rubber, and butyl rubber at various temperatures by gravimetric method. Modified thermogravimetric analysis system was built and used. The geometry of the samples was approximating that of the infinite two-sided plane sheet of certain thickness. The coefficients of Water Vapor diffusion in polymers were deduced by comparing the experimentally monitored kinetics and kinetics computed using diffusion coefficients as adjustable parameters. The activation energies of Water Vapor diffusion in these polymers were deduced in the temperature range from 30 to 75 °C. The activation energy of diffusion was 45.9 kJ mol^−1 in bromobutyl rubber, 46.4 kJ mol^−1 in butyl rubber, 60.3 kJ mol^−1 in EPDM rubber, and 43.5 kJ mol^−1 in MABS. Compensation effect was observed for Water Vapor diffusion in this series of polymers. Compensation effect parameters were determined to be, a = −23.9/ln(cm^2 s^−1) and b = 0.49/(mol kJ^−1) × ln(cm^2 s^−1), in fair agreement with published data for Water diffusion in polymers.
