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J. Etcheto - One of the best experts on this subject based on the ideXlab platform.
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Influence of gas Exchange Coefficient parameterisation on seasonal and regional variability of CO2 air‐sea fluxes
Geophysical Research Letters, 2002Co-Authors: Jacqueline Boutin, J. Etcheto, Liliane Merlivat, Y RangamaAbstract:[1] We examine the consequences of using four Exchange Coefficient versus wind speed parameterisations on the air-sea CO2 flux estimation, using one year of satellite wind speed measurements at global scale. Estimates of the global net CO2 flux to the ocean vary from 1.2 to 2.7 GtC yr−1. Additionnaly, we show 1) that the relative importance of outgassing and absorption fluxes is dependent on the form of the relationships due to a correlation between the direction of the flux and wind speed and 2) that differences on global net air-sea flux deduced from different K parameterisations are primarily due to parameterisation differences in the wind speed range between 4 and 17 ms−1.
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influence of gas Exchange Coefficient parameterisation on seasonal and regional variability of co2 air sea fluxes
Geophysical Research Letters, 2002Co-Authors: Jacqueline Boutin, J. Etcheto, Liliane Merlivat, Y RangamaAbstract:[1] We examine the consequences of using four Exchange Coefficient versus wind speed parameterisations on the air-sea CO2 flux estimation, using one year of satellite wind speed measurements at global scale. Estimates of the global net CO2 flux to the ocean vary from 1.2 to 2.7 GtC yr−1. Additionnaly, we show 1) that the relative importance of outgassing and absorption fluxes is dependent on the form of the relationships due to a correlation between the direction of the flux and wind speed and 2) that differences on global net air-sea flux deduced from different K parameterisations are primarily due to parameterisation differences in the wind speed range between 4 and 17 ms−1.
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long term variability of the air sea co2 Exchange Coefficient consequences for the co2 fluxes in the equatorial pacific ocean
Global Biogeochemical Cycles, 1997Co-Authors: Jacqueline Boutin, J. EtchetoAbstract:Global distributions of the air-sea CO2 Exchange Coefficient are deduced from the remotely sensed Geosat and special sensor microwave imager wind speeds from April 1985 to December 1992. The global 8-year average of the air-sea CO2 Exchange Coefficient is 3.15 10−2 mol m−2 yr−1 μatm−1. The peak-to-peak interannual variations are as large as the amplitude of the seasonal cycle in the tropical oceans and in the Antarctic Ocean, whereas in the northern high latitudes the seasonal variability dominates. The Exchange Coefficient time series is combined with air-sea CO2 partial pressure gradient that we extrapolate between 0°N and 5°S in the equatorial Pacific Ocean, and a zonal distribution of the air-sea CO2 fluxes is presented from 1985 to 1992. While the maximum of the CO2 partial pressure gradient is located in the eastern Pacific, the maximum of the flux is in the central Pacific because of low Exchange Coefficients in the eastern Pacific. The largest interannual variation, 3.5 mol m−2 yr−1, occurs in the central Pacific between 1987 and 1989 because the 1986–1987 El Nino event drives ocean partial pressure close to equilibrium with the atmosphere and the 1988–1989 La Nina event brings about both high partial pressure gradient and strong Exchange Coefficient.
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Long‐term variability of the air‐sea CO2 Exchange Coefficient: Consequences for the CO2 fluxes in the equatorial Pacific Ocean
Global Biogeochemical Cycles, 1997Co-Authors: Jacqueline Boutin, J. EtchetoAbstract:Global distributions of the air-sea CO2 Exchange Coefficient are deduced from the remotely sensed Geosat and special sensor microwave imager wind speeds from April 1985 to December 1992. The global 8-year average of the air-sea CO2 Exchange Coefficient is 3.15 10−2 mol m−2 yr−1 μatm−1. The peak-to-peak interannual variations are as large as the amplitude of the seasonal cycle in the tropical oceans and in the Antarctic Ocean, whereas in the northern high latitudes the seasonal variability dominates. The Exchange Coefficient time series is combined with air-sea CO2 partial pressure gradient that we extrapolate between 0°N and 5°S in the equatorial Pacific Ocean, and a zonal distribution of the air-sea CO2 fluxes is presented from 1985 to 1992. While the maximum of the CO2 partial pressure gradient is located in the eastern Pacific, the maximum of the flux is in the central Pacific because of low Exchange Coefficients in the eastern Pacific. The largest interannual variation, 3.5 mol m−2 yr−1, occurs in the central Pacific between 1987 and 1989 because the 1986–1987 El Nino event drives ocean partial pressure close to equilibrium with the atmosphere and the 1988–1989 La Nina event brings about both high partial pressure gradient and strong Exchange Coefficient.
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Intrinsic error in the air‐sea CO2 Exchange Coefficient resulting from the use of satellite wind speeds
Tellus B, 1991Co-Authors: Jacqueline Boutin, J. EtchetoAbstract:This paper is aimed at justifying the use of satellite wind speed measurements for the determination of the carbon dioxide Exchange Coefficient at the air–sea interface. We relate it to the wind speed using a relationship determined by Liss and Merlivat, which enables us to monitor the spatio-temporal variations of the CO 2 Exchange Coefficient on a global scale, using satellite measurements of the wind speed. Yet these measurements integrate the wind speed over areas having a diameter ranging from 25 to 100 km. Moreover, a satellite has a global coverage only after a few days and samples a given place every few days (usually 3 days). We simulate the spatial integration and temporal sampling of spacecraft measurements from in-situ wind speed measurements to infer the errors induced. While the space integration results in a negligible error (a few tenths of cm h -1 at most), a caveat should be given about the sampling error. It is of the order of the statistical error of a normal distribution, depending on the standard deviation and number of measurements. An example of the statistical error resulting from the use of 1 month of SEASAT scatterometer data is shown. Provided this caution about the statistical error is kept in mind and the space and time integration is properly chosen, satellite data, after careful validation of the wind speed retrieval, are well suited for long-term global survey of the CO 2 Exchange Coefficient space and time variations. The use of a relationship between the Exchange Coefficient and the wind speed, which accuracy is presently discussed, is the only way to access these variations. DOI: 10.1034/j.1600-0889.1991.00016.x
Jacqueline Boutin - One of the best experts on this subject based on the ideXlab platform.
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Influence of gas Exchange Coefficient parameterisation on seasonal and regional variability of CO2 air‐sea fluxes
Geophysical Research Letters, 2002Co-Authors: Jacqueline Boutin, J. Etcheto, Liliane Merlivat, Y RangamaAbstract:[1] We examine the consequences of using four Exchange Coefficient versus wind speed parameterisations on the air-sea CO2 flux estimation, using one year of satellite wind speed measurements at global scale. Estimates of the global net CO2 flux to the ocean vary from 1.2 to 2.7 GtC yr−1. Additionnaly, we show 1) that the relative importance of outgassing and absorption fluxes is dependent on the form of the relationships due to a correlation between the direction of the flux and wind speed and 2) that differences on global net air-sea flux deduced from different K parameterisations are primarily due to parameterisation differences in the wind speed range between 4 and 17 ms−1.
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influence of gas Exchange Coefficient parameterisation on seasonal and regional variability of co2 air sea fluxes
Geophysical Research Letters, 2002Co-Authors: Jacqueline Boutin, J. Etcheto, Liliane Merlivat, Y RangamaAbstract:[1] We examine the consequences of using four Exchange Coefficient versus wind speed parameterisations on the air-sea CO2 flux estimation, using one year of satellite wind speed measurements at global scale. Estimates of the global net CO2 flux to the ocean vary from 1.2 to 2.7 GtC yr−1. Additionnaly, we show 1) that the relative importance of outgassing and absorption fluxes is dependent on the form of the relationships due to a correlation between the direction of the flux and wind speed and 2) that differences on global net air-sea flux deduced from different K parameterisations are primarily due to parameterisation differences in the wind speed range between 4 and 17 ms−1.
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long term variability of the air sea co2 Exchange Coefficient consequences for the co2 fluxes in the equatorial pacific ocean
Global Biogeochemical Cycles, 1997Co-Authors: Jacqueline Boutin, J. EtchetoAbstract:Global distributions of the air-sea CO2 Exchange Coefficient are deduced from the remotely sensed Geosat and special sensor microwave imager wind speeds from April 1985 to December 1992. The global 8-year average of the air-sea CO2 Exchange Coefficient is 3.15 10−2 mol m−2 yr−1 μatm−1. The peak-to-peak interannual variations are as large as the amplitude of the seasonal cycle in the tropical oceans and in the Antarctic Ocean, whereas in the northern high latitudes the seasonal variability dominates. The Exchange Coefficient time series is combined with air-sea CO2 partial pressure gradient that we extrapolate between 0°N and 5°S in the equatorial Pacific Ocean, and a zonal distribution of the air-sea CO2 fluxes is presented from 1985 to 1992. While the maximum of the CO2 partial pressure gradient is located in the eastern Pacific, the maximum of the flux is in the central Pacific because of low Exchange Coefficients in the eastern Pacific. The largest interannual variation, 3.5 mol m−2 yr−1, occurs in the central Pacific between 1987 and 1989 because the 1986–1987 El Nino event drives ocean partial pressure close to equilibrium with the atmosphere and the 1988–1989 La Nina event brings about both high partial pressure gradient and strong Exchange Coefficient.
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Long‐term variability of the air‐sea CO2 Exchange Coefficient: Consequences for the CO2 fluxes in the equatorial Pacific Ocean
Global Biogeochemical Cycles, 1997Co-Authors: Jacqueline Boutin, J. EtchetoAbstract:Global distributions of the air-sea CO2 Exchange Coefficient are deduced from the remotely sensed Geosat and special sensor microwave imager wind speeds from April 1985 to December 1992. The global 8-year average of the air-sea CO2 Exchange Coefficient is 3.15 10−2 mol m−2 yr−1 μatm−1. The peak-to-peak interannual variations are as large as the amplitude of the seasonal cycle in the tropical oceans and in the Antarctic Ocean, whereas in the northern high latitudes the seasonal variability dominates. The Exchange Coefficient time series is combined with air-sea CO2 partial pressure gradient that we extrapolate between 0°N and 5°S in the equatorial Pacific Ocean, and a zonal distribution of the air-sea CO2 fluxes is presented from 1985 to 1992. While the maximum of the CO2 partial pressure gradient is located in the eastern Pacific, the maximum of the flux is in the central Pacific because of low Exchange Coefficients in the eastern Pacific. The largest interannual variation, 3.5 mol m−2 yr−1, occurs in the central Pacific between 1987 and 1989 because the 1986–1987 El Nino event drives ocean partial pressure close to equilibrium with the atmosphere and the 1988–1989 La Nina event brings about both high partial pressure gradient and strong Exchange Coefficient.
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Intrinsic error in the air‐sea CO2 Exchange Coefficient resulting from the use of satellite wind speeds
Tellus B, 1991Co-Authors: Jacqueline Boutin, J. EtchetoAbstract:This paper is aimed at justifying the use of satellite wind speed measurements for the determination of the carbon dioxide Exchange Coefficient at the air–sea interface. We relate it to the wind speed using a relationship determined by Liss and Merlivat, which enables us to monitor the spatio-temporal variations of the CO 2 Exchange Coefficient on a global scale, using satellite measurements of the wind speed. Yet these measurements integrate the wind speed over areas having a diameter ranging from 25 to 100 km. Moreover, a satellite has a global coverage only after a few days and samples a given place every few days (usually 3 days). We simulate the spatial integration and temporal sampling of spacecraft measurements from in-situ wind speed measurements to infer the errors induced. While the space integration results in a negligible error (a few tenths of cm h -1 at most), a caveat should be given about the sampling error. It is of the order of the statistical error of a normal distribution, depending on the standard deviation and number of measurements. An example of the statistical error resulting from the use of 1 month of SEASAT scatterometer data is shown. Provided this caution about the statistical error is kept in mind and the space and time integration is properly chosen, satellite data, after careful validation of the wind speed retrieval, are well suited for long-term global survey of the CO 2 Exchange Coefficient space and time variations. The use of a relationship between the Exchange Coefficient and the wind speed, which accuracy is presently discussed, is the only way to access these variations. DOI: 10.1034/j.1600-0889.1991.00016.x
Y Rangama - One of the best experts on this subject based on the ideXlab platform.
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influence of gas Exchange Coefficient parameterisation on seasonal and regional variability of co2 air sea fluxes
Geophysical Research Letters, 2002Co-Authors: Jacqueline Boutin, J. Etcheto, Liliane Merlivat, Y RangamaAbstract:[1] We examine the consequences of using four Exchange Coefficient versus wind speed parameterisations on the air-sea CO2 flux estimation, using one year of satellite wind speed measurements at global scale. Estimates of the global net CO2 flux to the ocean vary from 1.2 to 2.7 GtC yr−1. Additionnaly, we show 1) that the relative importance of outgassing and absorption fluxes is dependent on the form of the relationships due to a correlation between the direction of the flux and wind speed and 2) that differences on global net air-sea flux deduced from different K parameterisations are primarily due to parameterisation differences in the wind speed range between 4 and 17 ms−1.
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Influence of gas Exchange Coefficient parameterisation on seasonal and regional variability of CO2 air‐sea fluxes
Geophysical Research Letters, 2002Co-Authors: Jacqueline Boutin, J. Etcheto, Liliane Merlivat, Y RangamaAbstract:[1] We examine the consequences of using four Exchange Coefficient versus wind speed parameterisations on the air-sea CO2 flux estimation, using one year of satellite wind speed measurements at global scale. Estimates of the global net CO2 flux to the ocean vary from 1.2 to 2.7 GtC yr−1. Additionnaly, we show 1) that the relative importance of outgassing and absorption fluxes is dependent on the form of the relationships due to a correlation between the direction of the flux and wind speed and 2) that differences on global net air-sea flux deduced from different K parameterisations are primarily due to parameterisation differences in the wind speed range between 4 and 17 ms−1.
Liliane Merlivat - One of the best experts on this subject based on the ideXlab platform.
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Influence of gas Exchange Coefficient parameterisation on seasonal and regional variability of CO2 air‐sea fluxes
Geophysical Research Letters, 2002Co-Authors: Jacqueline Boutin, J. Etcheto, Liliane Merlivat, Y RangamaAbstract:[1] We examine the consequences of using four Exchange Coefficient versus wind speed parameterisations on the air-sea CO2 flux estimation, using one year of satellite wind speed measurements at global scale. Estimates of the global net CO2 flux to the ocean vary from 1.2 to 2.7 GtC yr−1. Additionnaly, we show 1) that the relative importance of outgassing and absorption fluxes is dependent on the form of the relationships due to a correlation between the direction of the flux and wind speed and 2) that differences on global net air-sea flux deduced from different K parameterisations are primarily due to parameterisation differences in the wind speed range between 4 and 17 ms−1.
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influence of gas Exchange Coefficient parameterisation on seasonal and regional variability of co2 air sea fluxes
Geophysical Research Letters, 2002Co-Authors: Jacqueline Boutin, J. Etcheto, Liliane Merlivat, Y RangamaAbstract:[1] We examine the consequences of using four Exchange Coefficient versus wind speed parameterisations on the air-sea CO2 flux estimation, using one year of satellite wind speed measurements at global scale. Estimates of the global net CO2 flux to the ocean vary from 1.2 to 2.7 GtC yr−1. Additionnaly, we show 1) that the relative importance of outgassing and absorption fluxes is dependent on the form of the relationships due to a correlation between the direction of the flux and wind speed and 2) that differences on global net air-sea flux deduced from different K parameterisations are primarily due to parameterisation differences in the wind speed range between 4 and 17 ms−1.
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seasonal variation of the co2 Exchange Coefficient over the global ocean using satellite wind speed measurements
Tellus B, 1991Co-Authors: J. Etcheto, Jacqueline Boutin, Liliane MerlivatAbstract:We used one year (July 1987 to June 1988) of wind speed measurements made by the microwave radiometer SSM/I to determine the CO 2 Exchange Coefficient between air and sea on a global scale through the Liss and Merlivat relationship. We determined the seasonal variation in every region of the world ocean. It can be as high as a factor of 4 in some areas. An estimate of the accuracy of the retrieved wind speeds showed that this variation is likely to be underestimated. The global averaged CO 2 Exchange Coefficient obtained is 3.34. 10 -2 mol m -2 yr -1 µ atm -1 , close to previous estimates. A study of the errors on the retrieved wind speed showed that the Exchange Coefficient is likely to be underestimated and could be as high as 4 10 -2 mol m -2 yr -1 µ atm -1 . We combined these results with various estimates of the annual CO 2 partial pressure gradient at the air sea surface and get a net flux absorbed by the ocean. The flux so determined is not meaningful, however, since the covariant variability of the Exchange Coefficient and of the CO 2 partial pressure gradient is not taken into account. DOI: 10.1034/j.1600-0889.1991.00017.x
N. Richet - One of the best experts on this subject based on the ideXlab platform.
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oxygen semi permeation oxygen diffusion and surface Exchange Coefficient of la 1 x srxfe 1 y gayo3 δ perovskite membranes
Journal of Membrane Science, 2010Co-Authors: Pierre-marie Geffroy, Sébastien Fourcade, Aurélien Vivet, Jean-marc Bassat, Thierry Chartier, P Del Gallo, N. RichetAbstract:Abstract Mixed ionic and electronic conductors (MIEC) have presented great economical and environmental interests for these last years because of their potential applications for electrode materials in solid oxide fuel cell and for oxygen separation form air such as in catalytic membrane reactors for methane conversion into syngas (H 2 –CO mixture) (A.F. Sammells, M. Schwartz, R.A. Mackay, T.F. Barton, D.R. Peterson [1] , U. Balachandran, J.T. Dusek, R.L. Mieville, R.B. Poeppel, M.S. Kleefisch [2] , H.J.M. Bouwmeester, B.A. Boukamp [3] ). A good compromise between oxygen permeability, chemical stability and physical properties is required to optimize the process. La (1− x ) Sr x Fe (1− y ) Ga y O 3− δ materials fulfill this requirement and were retained as membrane for catalytic membrane reactor (CMR) (Y. Teraoka [4] , G. Etchegoyen, T. Chartier [5] ). Oxygen semi-permeations through La (1− x ) Sr x Fe (1− y ) Ga y O 3− δ membranes have been measured under various oxygen partial pressure gradients from 973 K to 1273 K, and compared with the values obtained by isotopic oxygen Exchange depth experiments (S. Kim, S. Wang, X. Chen, Y.L. Yang, N. Wu, A. Ignatiev, A.J. Jacobson, and B. Abeles [6] ). Those results lead to a better understanding of the oxygen transport through the membrane and the influence of Sr and Ga amounts on oxygen semi-permeation through the membrane. The influence of Ga amount is not limited to the improvement of dimensional stabilities but it also increases oxygen diffusion and surface Exchange kinetic. This paper suggests that La 0.6 Sr 0.4 Fe 0.6 Ga 0.4 O 3− δ perovskite is a very good compromise for membrane reactor materials and opens new perspectives on membrane architecture development.
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Oxygen semi-permeation, oxygen diffusion and surface Exchange Coefficient of La(1−x)SrxFe(1−y)GayO3−δ perovskite membranes
Journal of Membrane Science, 2010Co-Authors: Pierre-marie Geffroy, Sébastien Fourcade, Aurélien Vivet, Pascal Del-gallo, Jean-marc Bassat, Thierry Chartier, N. RichetAbstract:Mixed ionic and electronic conductors (MIEC) have presented great economical and environmental interests for these last years because of their potential applications for electrode materials in solid oxide fuel cell and for oxygen separation form air such as in catalytic membrane reactors for methane conversion into syngas (H2–CO mixture) (A.F. Sammells, M. Schwartz, R.A. Mackay, T.F. Barton, D.R. Peterson [1], U. Balachandran, J.T. Dusek, R.L. Mieville, R.B. Poeppel, M.S. Kleefisch [2], H.J.M. Bouwmeester, B.A. Boukamp [3]). A good compromise between oxygen permeability, chemical stability and physical properties is required to optimize the process. La(1−x)SrxFe(1−y)GayO3−δ materials fulfill this requirement and were retained as membrane for catalytic membrane reactor (CMR) (Y. Teraoka [4], G. Etchegoyen, T. Chartier [5]). Oxygen semi-permeations through La(1−x)SrxFe(1−y)GayO3−δ membranes have been measured under various oxygen partial pressure gradients from 973 K to 1273 K, and compared with the values obtained by isotopic oxygen Exchange depth experiments (S. Kim, S. Wang, X. Chen, Y.L. Yang, N. Wu, A. Ignatiev, A.J. Jacobson, and B. Abeles [6]). Those results lead to a better understanding of the oxygen transport through the membrane and the influence of Sr and Ga amounts on oxygen semi-permeation through the membrane. The influence of Ga amount is not limited to the improvement of dimensional stabilities but it also increases oxygen diffusion and surface Exchange kinetic. This paper suggests that La0.6Sr0.4Fe0.6Ga0.4O3−δ perovskite is a very good compromise for membrane reactor materials and opens new perspectives on membrane architecture development.
