Reanalysis representation of low-level winds in the Antarctic near-coastal region
Low-level easterly winds encircling Antarctica help drive coastal currents which modify transport of circumpolar deep water to ice shelves, as well as the formation and distribution of sea ice. Reanalysis datasets are especially important at high southern latitudes where observations are few. Here,...
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ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00062260 2023-05-15T13:49:21+02:00 Reanalysis representation of low-level winds in the Antarctic near-coastal region Caton Harrison, Thomas Biri, Stavroula Bracegirdle, Thomas J. King, John C. Kent, Elizabeth C. Vignon, Étienne Turner, John 2022-08 electronic https://doi.org/10.5194/egusphere-2022-693 https://noa.gwlb.de/receive/cop_mods_00062260 https://egusphere.copernicus.org/preprints/egusphere-2022-693/egusphere-2022-693.pdf eng eng Copernicus Publications https://doi.org/10.5194/egusphere-2022-693 https://noa.gwlb.de/receive/cop_mods_00062260 https://egusphere.copernicus.org/preprints/egusphere-2022-693/egusphere-2022-693.pdf https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/restrictedAccess CC-BY article Verlagsveröffentlichung article Text doc-type:article 2022 ftnonlinearchiv https://doi.org/10.5194/egusphere-2022-693 2022-08-14T23:11:52Z Low-level easterly winds encircling Antarctica help drive coastal currents which modify transport of circumpolar deep water to ice shelves, as well as the formation and distribution of sea ice. Reanalysis datasets are especially important at high southern latitudes where observations are few. Here, we investigate the representation of the mean state and short-term variability of coastal easterlies in three recent reanalyses, ERA5, MERRA-2 and JRA-55. Reanalysed winds are compared with summertime marine surface wind observations from the ASCAT scatterometer and surface and upper air measurements from coastal stations. Reanalysis coastal easterlies correlate highly with ASCAT (r=0.91, 0.89 and 0.85 for ERA5, MERRA-2 and JRA-55 respectively) but notable wind speed biases are found close to the coastal margins, especially near complex orography and at high wind speeds. To characterise short-term variability, 12-hourly reanalysis and coastal station winds are composited using self-organising maps (SOMs), which cluster timesteps under similar synoptic and mesoscale influences. Reanalysis performance is sensitive to the flow configuration at stations near steep coastal slopes, where they fail to capture the magnitude of surface wind speed variability when synoptic forcing is weak and conditions favour katabatic forcing. ERA5 exhibits the best overall performance, has more realistic orography and a more realistic jet structure and temperature profile. These results demonstrate the regime behaviour of Antarctica’s coastal winds and indicate important features of the coastal winds which are not well characterised by reanalysis datasets. Article in Journal/Newspaper Antarc* Antarctic Antarctica Ice Shelves Sea ice Niedersächsisches Online-Archiv NOA Antarctic Merra ENVELOPE(12.615,12.615,65.816,65.816) The Antarctic |
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Niedersächsisches Online-Archiv NOA |
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ftnonlinearchiv |
language |
English |
topic |
article Verlagsveröffentlichung |
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article Verlagsveröffentlichung Caton Harrison, Thomas Biri, Stavroula Bracegirdle, Thomas J. King, John C. Kent, Elizabeth C. Vignon, Étienne Turner, John Reanalysis representation of low-level winds in the Antarctic near-coastal region |
topic_facet |
article Verlagsveröffentlichung |
description |
Low-level easterly winds encircling Antarctica help drive coastal currents which modify transport of circumpolar deep water to ice shelves, as well as the formation and distribution of sea ice. Reanalysis datasets are especially important at high southern latitudes where observations are few. Here, we investigate the representation of the mean state and short-term variability of coastal easterlies in three recent reanalyses, ERA5, MERRA-2 and JRA-55. Reanalysed winds are compared with summertime marine surface wind observations from the ASCAT scatterometer and surface and upper air measurements from coastal stations. Reanalysis coastal easterlies correlate highly with ASCAT (r=0.91, 0.89 and 0.85 for ERA5, MERRA-2 and JRA-55 respectively) but notable wind speed biases are found close to the coastal margins, especially near complex orography and at high wind speeds. To characterise short-term variability, 12-hourly reanalysis and coastal station winds are composited using self-organising maps (SOMs), which cluster timesteps under similar synoptic and mesoscale influences. Reanalysis performance is sensitive to the flow configuration at stations near steep coastal slopes, where they fail to capture the magnitude of surface wind speed variability when synoptic forcing is weak and conditions favour katabatic forcing. ERA5 exhibits the best overall performance, has more realistic orography and a more realistic jet structure and temperature profile. These results demonstrate the regime behaviour of Antarctica’s coastal winds and indicate important features of the coastal winds which are not well characterised by reanalysis datasets. |
format |
Article in Journal/Newspaper |
author |
Caton Harrison, Thomas Biri, Stavroula Bracegirdle, Thomas J. King, John C. Kent, Elizabeth C. Vignon, Étienne Turner, John |
author_facet |
Caton Harrison, Thomas Biri, Stavroula Bracegirdle, Thomas J. King, John C. Kent, Elizabeth C. Vignon, Étienne Turner, John |
author_sort |
Caton Harrison, Thomas |
title |
Reanalysis representation of low-level winds in the Antarctic near-coastal region |
title_short |
Reanalysis representation of low-level winds in the Antarctic near-coastal region |
title_full |
Reanalysis representation of low-level winds in the Antarctic near-coastal region |
title_fullStr |
Reanalysis representation of low-level winds in the Antarctic near-coastal region |
title_full_unstemmed |
Reanalysis representation of low-level winds in the Antarctic near-coastal region |
title_sort |
reanalysis representation of low-level winds in the antarctic near-coastal region |
publisher |
Copernicus Publications |
publishDate |
2022 |
url |
https://doi.org/10.5194/egusphere-2022-693 https://noa.gwlb.de/receive/cop_mods_00062260 https://egusphere.copernicus.org/preprints/egusphere-2022-693/egusphere-2022-693.pdf |
long_lat |
ENVELOPE(12.615,12.615,65.816,65.816) |
geographic |
Antarctic Merra The Antarctic |
geographic_facet |
Antarctic Merra The Antarctic |
genre |
Antarc* Antarctic Antarctica Ice Shelves Sea ice |
genre_facet |
Antarc* Antarctic Antarctica Ice Shelves Sea ice |
op_relation |
https://doi.org/10.5194/egusphere-2022-693 https://noa.gwlb.de/receive/cop_mods_00062260 https://egusphere.copernicus.org/preprints/egusphere-2022-693/egusphere-2022-693.pdf |
op_rights |
https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/restrictedAccess |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.5194/egusphere-2022-693 |
_version_ |
1766251234647343104 |