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, and the formation and distribution of sea ice. Reanalysis datasets are especially important at high southern latitudes where observations are few. Here, we inve...
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ftdoajarticles:oai:doaj.org/article:b026b36721b2499b93fe3076bc3b6bd7 2023-05-15T13:44:00+02:00 Reanalysis representation of low-level winds in the Antarctic near-coastal region T. Caton Harrison S. Biri T. J. Bracegirdle J. C. King E. C. Kent É. Vignon J. Turner 2022-12-01T00:00:00Z https://doi.org/10.5194/wcd-3-1415-2022 https://doaj.org/article/b026b36721b2499b93fe3076bc3b6bd7 EN eng Copernicus Publications https://wcd.copernicus.org/articles/3/1415/2022/wcd-3-1415-2022.pdf https://doaj.org/toc/2698-4016 doi:10.5194/wcd-3-1415-2022 2698-4016 https://doaj.org/article/b026b36721b2499b93fe3076bc3b6bd7 Weather and Climate Dynamics, Vol 3, Pp 1415-1437 (2022) Meteorology. Climatology QC851-999 article 2022 ftdoajarticles https://doi.org/10.5194/wcd-3-1415-2022 2022-12-30T20:17:33Z Low-level easterly winds encircling Antarctica help drive coastal currents which modify transport of circumpolar deep water to ice shelves, and 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 near-surface wind observations from the Advanced Scatterometer (ASCAT) 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 near-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 Directory of Open Access Journals: DOAJ Articles Antarctic Merra ENVELOPE(12.615,12.615,65.816,65.816) The Antarctic Weather and Climate Dynamics 3 4 1415 1437 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Meteorology. Climatology QC851-999 |
spellingShingle |
Meteorology. Climatology QC851-999 T. Caton Harrison S. Biri T. J. Bracegirdle J. C. King E. C. Kent É. Vignon J. Turner Reanalysis representation of low-level winds in the Antarctic near-coastal region |
topic_facet |
Meteorology. Climatology QC851-999 |
description |
Low-level easterly winds encircling Antarctica help drive coastal currents which modify transport of circumpolar deep water to ice shelves, and 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 near-surface wind observations from the Advanced Scatterometer (ASCAT) 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 near-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 |
T. Caton Harrison S. Biri T. J. Bracegirdle J. C. King E. C. Kent É. Vignon J. Turner |
author_facet |
T. Caton Harrison S. Biri T. J. Bracegirdle J. C. King E. C. Kent É. Vignon J. Turner |
author_sort |
T. Caton Harrison |
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/wcd-3-1415-2022 https://doaj.org/article/b026b36721b2499b93fe3076bc3b6bd7 |
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_source |
Weather and Climate Dynamics, Vol 3, Pp 1415-1437 (2022) |
op_relation |
https://wcd.copernicus.org/articles/3/1415/2022/wcd-3-1415-2022.pdf https://doaj.org/toc/2698-4016 doi:10.5194/wcd-3-1415-2022 2698-4016 https://doaj.org/article/b026b36721b2499b93fe3076bc3b6bd7 |
op_doi |
https://doi.org/10.5194/wcd-3-1415-2022 |
container_title |
Weather and Climate Dynamics |
container_volume |
3 |
container_issue |
4 |
container_start_page |
1415 |
op_container_end_page |
1437 |
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1766195745979891712 |