Nonequilibrium Fractionation During Ice Cloud Formation in iCAM5: Evaluating the Common Parameterization of Supersaturation as a Linear Function of Temperature
Abstract Supersaturation with respect to ice determines the strength of nonequilibrium fractionation during vapor deposition onto ice or snow and therefore influences the water isotopic composition of vapor and precipitation in cold environments. Historically, most general circulation models formed...
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ftdoajarticles:oai:doaj.org/article:b5bd45e3f0154396b8f3c0f3a97af4b8 2023-05-15T13:32:48+02:00 Nonequilibrium Fractionation During Ice Cloud Formation in iCAM5: Evaluating the Common Parameterization of Supersaturation as a Linear Function of Temperature Marina Dütsch Peter N. Blossey Eric J. Steig Jesse M. Nusbaumer 2019-11-01T00:00:00Z https://doi.org/10.1029/2019MS001764 https://doaj.org/article/b5bd45e3f0154396b8f3c0f3a97af4b8 EN eng American Geophysical Union (AGU) https://doi.org/10.1029/2019MS001764 https://doaj.org/toc/1942-2466 1942-2466 doi:10.1029/2019MS001764 https://doaj.org/article/b5bd45e3f0154396b8f3c0f3a97af4b8 Journal of Advances in Modeling Earth Systems, Vol 11, Iss 11, Pp 3777-3793 (2019) stable water isotopes deuterium excess supersaturation Antarctica ice clouds Physical geography GB3-5030 Oceanography GC1-1581 article 2019 ftdoajarticles https://doi.org/10.1029/2019MS001764 2022-12-31T12:59:45Z Abstract Supersaturation with respect to ice determines the strength of nonequilibrium fractionation during vapor deposition onto ice or snow and therefore influences the water isotopic composition of vapor and precipitation in cold environments. Historically, most general circulation models formed clouds through saturation adjustment and therefore prevented supersaturation. To match the observed isotopic content, especially the deuterium excess, of snow in polar regions, the saturation ratio with respect to ice (Si) was parameterized, usually by assuming a linear dependence of Si on temperature. The Community Atmosphere Model Version 5 (CAM5) no longer applies saturation adjustment for the ice phase and thus allows ice supersaturation. Here, we adapt the isotope‐enabled version of CAM5 to compute nonequilibrium fractionation in ice and mixed‐phase clouds based on Si from the CAM5 microphysics and use it to evaluate the common parameterization of Si. Our results show a wide range of Si predicted by the CAM5 microphysics and reflected in the simulated deuterium excess of Antarctic precipitation; this is overly simplified by the linear parameterization. Nevertheless, a linear function, when properly tuned, can reproduce the average observed relationship between δD and deuterium excess reasonably well. However, only the model‐predicted Si can capture changes in microphysical conditions under different climate states that are not due to changes in temperature. Furthermore, parametric sensitivity tests show that with the model‐predicted Si, water isotopes are more closely tied to the model microphysics and can therefore constrain uncertain microphysical parameters. Article in Journal/Newspaper Antarc* Antarctic Antarctica Directory of Open Access Journals: DOAJ Articles Antarctic Journal of Advances in Modeling Earth Systems 11 11 3777 3793 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
stable water isotopes deuterium excess supersaturation Antarctica ice clouds Physical geography GB3-5030 Oceanography GC1-1581 |
spellingShingle |
stable water isotopes deuterium excess supersaturation Antarctica ice clouds Physical geography GB3-5030 Oceanography GC1-1581 Marina Dütsch Peter N. Blossey Eric J. Steig Jesse M. Nusbaumer Nonequilibrium Fractionation During Ice Cloud Formation in iCAM5: Evaluating the Common Parameterization of Supersaturation as a Linear Function of Temperature |
topic_facet |
stable water isotopes deuterium excess supersaturation Antarctica ice clouds Physical geography GB3-5030 Oceanography GC1-1581 |
description |
Abstract Supersaturation with respect to ice determines the strength of nonequilibrium fractionation during vapor deposition onto ice or snow and therefore influences the water isotopic composition of vapor and precipitation in cold environments. Historically, most general circulation models formed clouds through saturation adjustment and therefore prevented supersaturation. To match the observed isotopic content, especially the deuterium excess, of snow in polar regions, the saturation ratio with respect to ice (Si) was parameterized, usually by assuming a linear dependence of Si on temperature. The Community Atmosphere Model Version 5 (CAM5) no longer applies saturation adjustment for the ice phase and thus allows ice supersaturation. Here, we adapt the isotope‐enabled version of CAM5 to compute nonequilibrium fractionation in ice and mixed‐phase clouds based on Si from the CAM5 microphysics and use it to evaluate the common parameterization of Si. Our results show a wide range of Si predicted by the CAM5 microphysics and reflected in the simulated deuterium excess of Antarctic precipitation; this is overly simplified by the linear parameterization. Nevertheless, a linear function, when properly tuned, can reproduce the average observed relationship between δD and deuterium excess reasonably well. However, only the model‐predicted Si can capture changes in microphysical conditions under different climate states that are not due to changes in temperature. Furthermore, parametric sensitivity tests show that with the model‐predicted Si, water isotopes are more closely tied to the model microphysics and can therefore constrain uncertain microphysical parameters. |
format |
Article in Journal/Newspaper |
author |
Marina Dütsch Peter N. Blossey Eric J. Steig Jesse M. Nusbaumer |
author_facet |
Marina Dütsch Peter N. Blossey Eric J. Steig Jesse M. Nusbaumer |
author_sort |
Marina Dütsch |
title |
Nonequilibrium Fractionation During Ice Cloud Formation in iCAM5: Evaluating the Common Parameterization of Supersaturation as a Linear Function of Temperature |
title_short |
Nonequilibrium Fractionation During Ice Cloud Formation in iCAM5: Evaluating the Common Parameterization of Supersaturation as a Linear Function of Temperature |
title_full |
Nonequilibrium Fractionation During Ice Cloud Formation in iCAM5: Evaluating the Common Parameterization of Supersaturation as a Linear Function of Temperature |
title_fullStr |
Nonequilibrium Fractionation During Ice Cloud Formation in iCAM5: Evaluating the Common Parameterization of Supersaturation as a Linear Function of Temperature |
title_full_unstemmed |
Nonequilibrium Fractionation During Ice Cloud Formation in iCAM5: Evaluating the Common Parameterization of Supersaturation as a Linear Function of Temperature |
title_sort |
nonequilibrium fractionation during ice cloud formation in icam5: evaluating the common parameterization of supersaturation as a linear function of temperature |
publisher |
American Geophysical Union (AGU) |
publishDate |
2019 |
url |
https://doi.org/10.1029/2019MS001764 https://doaj.org/article/b5bd45e3f0154396b8f3c0f3a97af4b8 |
geographic |
Antarctic |
geographic_facet |
Antarctic |
genre |
Antarc* Antarctic Antarctica |
genre_facet |
Antarc* Antarctic Antarctica |
op_source |
Journal of Advances in Modeling Earth Systems, Vol 11, Iss 11, Pp 3777-3793 (2019) |
op_relation |
https://doi.org/10.1029/2019MS001764 https://doaj.org/toc/1942-2466 1942-2466 doi:10.1029/2019MS001764 https://doaj.org/article/b5bd45e3f0154396b8f3c0f3a97af4b8 |
op_doi |
https://doi.org/10.1029/2019MS001764 |
container_title |
Journal of Advances in Modeling Earth Systems |
container_volume |
11 |
container_issue |
11 |
container_start_page |
3777 |
op_container_end_page |
3793 |
_version_ |
1766035934895144960 |