Regional and seasonal variations of the double-ITCZ bias in CMIP5 models
Current climate models represent the zonal- and annual-mean intertropical convergence zone (ITCZ) position in a biased way, with an unrealistic double precipitation peak straddling the equator in the ensemble mean over the models. This bias is seasonally and regionally localized. It results primaril...
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ftcaltechauth:oai:authors.library.caltech.edu:87564 2023-05-15T17:34:36+02:00 Regional and seasonal variations of the double-ITCZ bias in CMIP5 models Adam, Ori Schneider, Tapio Brient, Florent 2018-07 https://authors.library.caltech.edu/87564/ https://resolver.caltech.edu/CaltechAUTHORS:20180705-143240657 unknown Springer Adam, Ori and Schneider, Tapio and Brient, Florent (2018) Regional and seasonal variations of the double-ITCZ bias in CMIP5 models. Climate Dynamics, 51 (1-2). pp. 101-117. ISSN 0930-7575. doi:10.1007/s00382-017-3909-1. https://resolver.caltech.edu/CaltechAUTHORS:20180705-143240657 <https://resolver.caltech.edu/CaltechAUTHORS:20180705-143240657> Article PeerReviewed 2018 ftcaltechauth https://doi.org/10.1007/s00382-017-3909-1 2021-11-18T18:46:32Z Current climate models represent the zonal- and annual-mean intertropical convergence zone (ITCZ) position in a biased way, with an unrealistic double precipitation peak straddling the equator in the ensemble mean over the models. This bias is seasonally and regionally localized. It results primarily from two regions: the eastern Pacific and Atlantic (EPA), where the ITCZ in boreal winter and spring is displaced farther south than is observed; and the western Pacific (WP), where a more pronounced and wider than observed double ITCZ straddles the equator year-round. Additionally, the precipitation associated with the ascending branches of the zonal overturning circulations (e.g., Walker circulation) in the Pacific and Atlantic sectors is shifted westward. We interpret these biases in light of recent theories that relate the ITCZ position to the atmospheric energy budget. WP biases are associated with the well known Pacific cold tongue bias, which, in turn, is linked to atmospheric net energy input biases near the equator. In contrast, EPA biases are shown to be associated with a positive bias in the cross-equatorial divergent atmospheric energy transport during boreal winter and spring, with two potential sources: tropical biases associated with equatorial sea surface temperatures (SSTs) and tropical low clouds, and extratropical biases associated with Southern Ocean clouds and north Atlantic SST. The distinct seasonal and regional characteristics of WP and EPA biases and the differences in their associated energy budget biases suggest that the biases in the two sectors involve different mechanisms and potentially different sources. Article in Journal/Newspaper North Atlantic Southern Ocean Caltech Authors (California Institute of Technology) Pacific Southern Ocean Climate Dynamics 51 1-2 101 117 |
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Caltech Authors (California Institute of Technology) |
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description |
Current climate models represent the zonal- and annual-mean intertropical convergence zone (ITCZ) position in a biased way, with an unrealistic double precipitation peak straddling the equator in the ensemble mean over the models. This bias is seasonally and regionally localized. It results primarily from two regions: the eastern Pacific and Atlantic (EPA), where the ITCZ in boreal winter and spring is displaced farther south than is observed; and the western Pacific (WP), where a more pronounced and wider than observed double ITCZ straddles the equator year-round. Additionally, the precipitation associated with the ascending branches of the zonal overturning circulations (e.g., Walker circulation) in the Pacific and Atlantic sectors is shifted westward. We interpret these biases in light of recent theories that relate the ITCZ position to the atmospheric energy budget. WP biases are associated with the well known Pacific cold tongue bias, which, in turn, is linked to atmospheric net energy input biases near the equator. In contrast, EPA biases are shown to be associated with a positive bias in the cross-equatorial divergent atmospheric energy transport during boreal winter and spring, with two potential sources: tropical biases associated with equatorial sea surface temperatures (SSTs) and tropical low clouds, and extratropical biases associated with Southern Ocean clouds and north Atlantic SST. The distinct seasonal and regional characteristics of WP and EPA biases and the differences in their associated energy budget biases suggest that the biases in the two sectors involve different mechanisms and potentially different sources. |
format |
Article in Journal/Newspaper |
author |
Adam, Ori Schneider, Tapio Brient, Florent |
spellingShingle |
Adam, Ori Schneider, Tapio Brient, Florent Regional and seasonal variations of the double-ITCZ bias in CMIP5 models |
author_facet |
Adam, Ori Schneider, Tapio Brient, Florent |
author_sort |
Adam, Ori |
title |
Regional and seasonal variations of the double-ITCZ bias in CMIP5 models |
title_short |
Regional and seasonal variations of the double-ITCZ bias in CMIP5 models |
title_full |
Regional and seasonal variations of the double-ITCZ bias in CMIP5 models |
title_fullStr |
Regional and seasonal variations of the double-ITCZ bias in CMIP5 models |
title_full_unstemmed |
Regional and seasonal variations of the double-ITCZ bias in CMIP5 models |
title_sort |
regional and seasonal variations of the double-itcz bias in cmip5 models |
publisher |
Springer |
publishDate |
2018 |
url |
https://authors.library.caltech.edu/87564/ https://resolver.caltech.edu/CaltechAUTHORS:20180705-143240657 |
geographic |
Pacific Southern Ocean |
geographic_facet |
Pacific Southern Ocean |
genre |
North Atlantic Southern Ocean |
genre_facet |
North Atlantic Southern Ocean |
op_relation |
Adam, Ori and Schneider, Tapio and Brient, Florent (2018) Regional and seasonal variations of the double-ITCZ bias in CMIP5 models. Climate Dynamics, 51 (1-2). pp. 101-117. ISSN 0930-7575. doi:10.1007/s00382-017-3909-1. https://resolver.caltech.edu/CaltechAUTHORS:20180705-143240657 <https://resolver.caltech.edu/CaltechAUTHORS:20180705-143240657> |
op_doi |
https://doi.org/10.1007/s00382-017-3909-1 |
container_title |
Climate Dynamics |
container_volume |
51 |
container_issue |
1-2 |
container_start_page |
101 |
op_container_end_page |
117 |
_version_ |
1766133496883970048 |