Early-winter North Atlantic low-level jet latitude biases in climate models: implications for simulated regional atmosphere-ocean linkages
Climate model biases in the North Atlantic (NA) low-level tropospheric westerly jet are a major impediment to reliably representing variability of the NA climate system and its wider influence, in particular over western Europe. A major aspect of the biases is the occurrence of a prominent early-win...
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ftdoajarticles:oai:doaj.org/article:c8b0502211174c0eaa93d3cda5144b31 2023-09-05T13:21:25+02:00 Early-winter North Atlantic low-level jet latitude biases in climate models: implications for simulated regional atmosphere-ocean linkages Thomas J Bracegirdle Hua Lu Jon Robson 2021-01-01T00:00:00Z https://doi.org/10.1088/1748-9326/ac417f https://doaj.org/article/c8b0502211174c0eaa93d3cda5144b31 EN eng IOP Publishing https://doi.org/10.1088/1748-9326/ac417f https://doaj.org/toc/1748-9326 doi:10.1088/1748-9326/ac417f 1748-9326 https://doaj.org/article/c8b0502211174c0eaa93d3cda5144b31 Environmental Research Letters, Vol 17, Iss 1, p 014025 (2021) North Atlantic CMIP6 westerly jet sub-polar gyre atmosphere-ocean coupling Environmental technology. Sanitary engineering TD1-1066 Environmental sciences GE1-350 Science Q Physics QC1-999 article 2021 ftdoajarticles https://doi.org/10.1088/1748-9326/ac417f 2023-08-13T00:36:45Z Climate model biases in the North Atlantic (NA) low-level tropospheric westerly jet are a major impediment to reliably representing variability of the NA climate system and its wider influence, in particular over western Europe. A major aspect of the biases is the occurrence of a prominent early-winter equatorward jet bias in Coupled Model Inter-comparison Project Phase 5 (CMIP5) models that has implications for NA atmosphere-ocean coupling. Here we assess whether this bias is reduced in the new CMIP6 models and assess implications for model representation of NA atmosphere-ocean linkages, in particular over the sub-polar gyre (SPG) region. Historical simulations from the CMIP5 and CMIP6 model datasets were compared against reanalysis data over the period 1861–2005. The results show that the early-winter equatorward bias remains present in CMIP6 models, although with an approximately one-fifth reduction compared to CMIP5. The equatorward bias is mainly associated with a weaker-than-observed frequency of poleward excursions of the jet to its northern position. A potential explanation is provided through the identification of a strong link between NA jet latitude bias and systematically too-weak model-simulated low-level baroclinicity over eastern North America in early-winter. CMIP models with larger equatorward jet biases exhibit weaker correlations between temporal variability in speed of the jet and sea surface conditions (sea surface temperatures and turbulent heat fluxes) over the SPG. The results imply that the early-winter equatorward bias in jet latitude in CMIP models could partially explain other known biases, such as the weaker-than-observed seasonal-decadal predictability of the NA climate system. Article in Journal/Newspaper North Atlantic Directory of Open Access Journals: DOAJ Articles Environmental Research Letters 17 1 014025 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
North Atlantic CMIP6 westerly jet sub-polar gyre atmosphere-ocean coupling Environmental technology. Sanitary engineering TD1-1066 Environmental sciences GE1-350 Science Q Physics QC1-999 |
spellingShingle |
North Atlantic CMIP6 westerly jet sub-polar gyre atmosphere-ocean coupling Environmental technology. Sanitary engineering TD1-1066 Environmental sciences GE1-350 Science Q Physics QC1-999 Thomas J Bracegirdle Hua Lu Jon Robson Early-winter North Atlantic low-level jet latitude biases in climate models: implications for simulated regional atmosphere-ocean linkages |
topic_facet |
North Atlantic CMIP6 westerly jet sub-polar gyre atmosphere-ocean coupling Environmental technology. Sanitary engineering TD1-1066 Environmental sciences GE1-350 Science Q Physics QC1-999 |
description |
Climate model biases in the North Atlantic (NA) low-level tropospheric westerly jet are a major impediment to reliably representing variability of the NA climate system and its wider influence, in particular over western Europe. A major aspect of the biases is the occurrence of a prominent early-winter equatorward jet bias in Coupled Model Inter-comparison Project Phase 5 (CMIP5) models that has implications for NA atmosphere-ocean coupling. Here we assess whether this bias is reduced in the new CMIP6 models and assess implications for model representation of NA atmosphere-ocean linkages, in particular over the sub-polar gyre (SPG) region. Historical simulations from the CMIP5 and CMIP6 model datasets were compared against reanalysis data over the period 1861–2005. The results show that the early-winter equatorward bias remains present in CMIP6 models, although with an approximately one-fifth reduction compared to CMIP5. The equatorward bias is mainly associated with a weaker-than-observed frequency of poleward excursions of the jet to its northern position. A potential explanation is provided through the identification of a strong link between NA jet latitude bias and systematically too-weak model-simulated low-level baroclinicity over eastern North America in early-winter. CMIP models with larger equatorward jet biases exhibit weaker correlations between temporal variability in speed of the jet and sea surface conditions (sea surface temperatures and turbulent heat fluxes) over the SPG. The results imply that the early-winter equatorward bias in jet latitude in CMIP models could partially explain other known biases, such as the weaker-than-observed seasonal-decadal predictability of the NA climate system. |
format |
Article in Journal/Newspaper |
author |
Thomas J Bracegirdle Hua Lu Jon Robson |
author_facet |
Thomas J Bracegirdle Hua Lu Jon Robson |
author_sort |
Thomas J Bracegirdle |
title |
Early-winter North Atlantic low-level jet latitude biases in climate models: implications for simulated regional atmosphere-ocean linkages |
title_short |
Early-winter North Atlantic low-level jet latitude biases in climate models: implications for simulated regional atmosphere-ocean linkages |
title_full |
Early-winter North Atlantic low-level jet latitude biases in climate models: implications for simulated regional atmosphere-ocean linkages |
title_fullStr |
Early-winter North Atlantic low-level jet latitude biases in climate models: implications for simulated regional atmosphere-ocean linkages |
title_full_unstemmed |
Early-winter North Atlantic low-level jet latitude biases in climate models: implications for simulated regional atmosphere-ocean linkages |
title_sort |
early-winter north atlantic low-level jet latitude biases in climate models: implications for simulated regional atmosphere-ocean linkages |
publisher |
IOP Publishing |
publishDate |
2021 |
url |
https://doi.org/10.1088/1748-9326/ac417f https://doaj.org/article/c8b0502211174c0eaa93d3cda5144b31 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Environmental Research Letters, Vol 17, Iss 1, p 014025 (2021) |
op_relation |
https://doi.org/10.1088/1748-9326/ac417f https://doaj.org/toc/1748-9326 doi:10.1088/1748-9326/ac417f 1748-9326 https://doaj.org/article/c8b0502211174c0eaa93d3cda5144b31 |
op_doi |
https://doi.org/10.1088/1748-9326/ac417f |
container_title |
Environmental Research Letters |
container_volume |
17 |
container_issue |
1 |
container_start_page |
014025 |
_version_ |
1776202033920999424 |