Surface air relative humidities spuriously exceeding 100% in CMIP5 model output and their impact on future projections
In 17 out of the 29 Phase 5 of Coupled Model Intercomparison Project (CMIP5) climate models examined in this work, near-surface air relative humidity (RH) frequently exceeded 100% with respect to ice in polar areas in winter. The degree of supersaturation varied considerably across the models, and t...
Published in: | Journal of Geophysical Research: Atmospheres |
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American Geophysical Union
2019
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Online Access: | http://hdl.handle.net/10138/308149 |
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HELDA – University of Helsinki Open Repository |
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ANTARCTICA LAND RISK ICE 114 Physical sciences |
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ANTARCTICA LAND RISK ICE 114 Physical sciences Ruosteenoja, Kimmo Jylha, Kirsti Räisänen, Jouni Mäkelä, Antti Surface air relative humidities spuriously exceeding 100% in CMIP5 model output and their impact on future projections |
topic_facet |
ANTARCTICA LAND RISK ICE 114 Physical sciences |
description |
In 17 out of the 29 Phase 5 of Coupled Model Intercomparison Project (CMIP5) climate models examined in this work, near-surface air relative humidity (RH) frequently exceeded 100% with respect to ice in polar areas in winter. The degree of supersaturation varied considerably across the models, and the same evidently applies to the causes of the phenomenon. Consultations with the modeling groups revealed three categories of explanations for supersaturation occurrence: specification of RH with respect to ice rather than liquid water; inconsistencies in the determination of specific humidity and air temperature for the near-surface level; and the nonlinearity of saturated specific humidity as a function of temperature. Modeled global warming tended to reduce the artificial supersaturations, inducing a spurious negative trend in the future RH change. For example, over East Antarctica under Representative Concentration Pathway 8.5, the multimodel mean RH would decrease by about 10% by the end of the ongoing century. Truncation of overly high RHs to a maximum value of 100% cut the RH response close to zero. In Siberia and northern North America, truncation even reversed the sign of the response. The institutes responsible for the CMIP6 model experiments should be aware of the supersaturation issue, and the algorithms used to produce near-surface RH should be developed to eliminate the problem before publishing the RH output data. Plain Language Summary In the atmosphere, observed relative humidity is between 0% and 100%. However, some climate models produce spurious higher than 100% humidities. The problem only concerns polar areas in winter. As temperatures rise in the future, such model-produced excessively high relative humidities partially vanish. Unfortunately, this induces a spurious negative trend in the future humidity projections. Such a spurious component in the simulated trend complicates discerning the real physically based trend. The spurious trend could be eliminated by truncating the portion of relative ... |
author2 |
Department of Physics |
format |
Article in Journal/Newspaper |
author |
Ruosteenoja, Kimmo Jylha, Kirsti Räisänen, Jouni Mäkelä, Antti |
author_facet |
Ruosteenoja, Kimmo Jylha, Kirsti Räisänen, Jouni Mäkelä, Antti |
author_sort |
Ruosteenoja, Kimmo |
title |
Surface air relative humidities spuriously exceeding 100% in CMIP5 model output and their impact on future projections |
title_short |
Surface air relative humidities spuriously exceeding 100% in CMIP5 model output and their impact on future projections |
title_full |
Surface air relative humidities spuriously exceeding 100% in CMIP5 model output and their impact on future projections |
title_fullStr |
Surface air relative humidities spuriously exceeding 100% in CMIP5 model output and their impact on future projections |
title_full_unstemmed |
Surface air relative humidities spuriously exceeding 100% in CMIP5 model output and their impact on future projections |
title_sort |
surface air relative humidities spuriously exceeding 100% in cmip5 model output and their impact on future projections |
publisher |
American Geophysical Union |
publishDate |
2019 |
url |
http://hdl.handle.net/10138/308149 |
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East Antarctica |
geographic_facet |
East Antarctica |
genre |
Antarc* Antarctica East Antarctica Siberia |
genre_facet |
Antarc* Antarctica East Antarctica Siberia |
op_relation |
10.1002/2017JD026909 This study has been performed under a contract (C3S_51_Lot4_FMI/DECM) for the Copernicus Climate Change Service. ECMWF implements this Service and the Copernicus Atmosphere Monitoring Service on behalf of the European Commission. Additional funding has been received from the Academy of Finland through the PLUMES project (decision 278067). The CMIP5 GCM data were downloaded from the Earth System Grid Federation (ESGF) data archive (http://esgf-node.llnl.gov/search/cmip5). All participating climate modeling groups are acknowledged for making their model output available through ESGF. Revisions induced by the comments presented by M. Juckes and an unknown reviewer have substantially deepened our insight into the subject. For information about near-surface RH calculations in the models, we are grateful for the following persons: A. Ackerman, I. Bethke, Y. Cheng, A. Del Genio, C. Fortelius, D. Ji, C. D. Jones, M. Kawamiya, K. Lo, Y. Lu, O. Seland, T. Toniazzo, E. Volodin, M. Watanabe, and S. Yukimoto, as well as for the GFDL Climate Model Info. As a part of this manuscript, an electronic supporting information file is available, containing figures displaying the influence of supersaturation on future projections for selected models. Also, maps of the ensemble-mean RH response using all 29 models are presented. Ruosteenoja , K , Jylha , K , Räisänen , J & Mäkelä , A 2017 , ' Surface air relative humidities spuriously exceeding 100% in CMIP5 model output and their impact on future projections ' , Journal of Geophysical Research : Atmospheres , vol. 122 , no. 18 , pp. 9557-9568 . https://doi.org/10.1002/2017JD026909 ORCID: /0000-0003-3657-1588/work/39925472 85031105270 39bf03aa-5d03-410b-8245-2f39ebe2b03c http://hdl.handle.net/10138/308149 000416388000001 |
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cc_by_nc_sa openAccess info:eu-repo/semantics/openAccess |
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Journal of Geophysical Research: Atmospheres |
container_volume |
122 |
container_issue |
18 |
container_start_page |
9557 |
op_container_end_page |
9568 |
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1787429673033007104 |
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ftunivhelsihelda:oai:helda.helsinki.fi:10138/308149 2024-01-07T09:39:28+01:00 Surface air relative humidities spuriously exceeding 100% in CMIP5 model output and their impact on future projections Ruosteenoja, Kimmo Jylha, Kirsti Räisänen, Jouni Mäkelä, Antti Department of Physics 2019-12-12T10:42:04Z 12 application/pdf http://hdl.handle.net/10138/308149 eng eng American Geophysical Union 10.1002/2017JD026909 This study has been performed under a contract (C3S_51_Lot4_FMI/DECM) for the Copernicus Climate Change Service. ECMWF implements this Service and the Copernicus Atmosphere Monitoring Service on behalf of the European Commission. Additional funding has been received from the Academy of Finland through the PLUMES project (decision 278067). The CMIP5 GCM data were downloaded from the Earth System Grid Federation (ESGF) data archive (http://esgf-node.llnl.gov/search/cmip5). All participating climate modeling groups are acknowledged for making their model output available through ESGF. Revisions induced by the comments presented by M. Juckes and an unknown reviewer have substantially deepened our insight into the subject. For information about near-surface RH calculations in the models, we are grateful for the following persons: A. Ackerman, I. Bethke, Y. Cheng, A. Del Genio, C. Fortelius, D. Ji, C. D. Jones, M. Kawamiya, K. Lo, Y. Lu, O. Seland, T. Toniazzo, E. Volodin, M. Watanabe, and S. Yukimoto, as well as for the GFDL Climate Model Info. As a part of this manuscript, an electronic supporting information file is available, containing figures displaying the influence of supersaturation on future projections for selected models. Also, maps of the ensemble-mean RH response using all 29 models are presented. Ruosteenoja , K , Jylha , K , Räisänen , J & Mäkelä , A 2017 , ' Surface air relative humidities spuriously exceeding 100% in CMIP5 model output and their impact on future projections ' , Journal of Geophysical Research : Atmospheres , vol. 122 , no. 18 , pp. 9557-9568 . https://doi.org/10.1002/2017JD026909 ORCID: /0000-0003-3657-1588/work/39925472 85031105270 39bf03aa-5d03-410b-8245-2f39ebe2b03c http://hdl.handle.net/10138/308149 000416388000001 cc_by_nc_sa openAccess info:eu-repo/semantics/openAccess ANTARCTICA LAND RISK ICE 114 Physical sciences Article publishedVersion 2019 ftunivhelsihelda 2023-12-14T00:02:09Z In 17 out of the 29 Phase 5 of Coupled Model Intercomparison Project (CMIP5) climate models examined in this work, near-surface air relative humidity (RH) frequently exceeded 100% with respect to ice in polar areas in winter. The degree of supersaturation varied considerably across the models, and the same evidently applies to the causes of the phenomenon. Consultations with the modeling groups revealed three categories of explanations for supersaturation occurrence: specification of RH with respect to ice rather than liquid water; inconsistencies in the determination of specific humidity and air temperature for the near-surface level; and the nonlinearity of saturated specific humidity as a function of temperature. Modeled global warming tended to reduce the artificial supersaturations, inducing a spurious negative trend in the future RH change. For example, over East Antarctica under Representative Concentration Pathway 8.5, the multimodel mean RH would decrease by about 10% by the end of the ongoing century. Truncation of overly high RHs to a maximum value of 100% cut the RH response close to zero. In Siberia and northern North America, truncation even reversed the sign of the response. The institutes responsible for the CMIP6 model experiments should be aware of the supersaturation issue, and the algorithms used to produce near-surface RH should be developed to eliminate the problem before publishing the RH output data. Plain Language Summary In the atmosphere, observed relative humidity is between 0% and 100%. However, some climate models produce spurious higher than 100% humidities. The problem only concerns polar areas in winter. As temperatures rise in the future, such model-produced excessively high relative humidities partially vanish. Unfortunately, this induces a spurious negative trend in the future humidity projections. Such a spurious component in the simulated trend complicates discerning the real physically based trend. The spurious trend could be eliminated by truncating the portion of relative ... Article in Journal/Newspaper Antarc* Antarctica East Antarctica Siberia HELDA – University of Helsinki Open Repository East Antarctica Journal of Geophysical Research: Atmospheres 122 18 9557 9568 |