Time-Varying Empirical Probability Densities of Southern Ocean Surface Winds: Linking the Leading Mode to SAM and QuantifyingWind Product Differences
AbstractSouthern Ocean (SO) surface winds are essential for ventilating the upper ocean by bringing heat and CO2 to the ocean interior. The relationships between mixed-layer ventilation, the Southern Annular Mode (SAM), and the storm tracks remain unclear because processes can be governed by short-t...
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2021
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Online Access: | https://escholarship.org/uc/item/8jf2z19v https://escholarship.org/content/qt8jf2z19v/qt8jf2z19v.pdf https://doi.org/10.1175/jcli-d-20-0629.1 |
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ftcdlib:oai:escholarship.org:ark:/13030/qt8jf2z19v 2024-09-15T18:37:08+00:00 Time-Varying Empirical Probability Densities of Southern Ocean Surface Winds: Linking the Leading Mode to SAM and QuantifyingWind Product Differences Hell, Momme C Cornuelle, Bruce D Gille, Sarah T Lutsko, Nicholas J 1 - 80 2021-04-07 application/pdf https://escholarship.org/uc/item/8jf2z19v https://escholarship.org/content/qt8jf2z19v/qt8jf2z19v.pdf https://doi.org/10.1175/jcli-d-20-0629.1 unknown eScholarship, University of California qt8jf2z19v https://escholarship.org/uc/item/8jf2z19v https://escholarship.org/content/qt8jf2z19v/qt8jf2z19v.pdf doi:10.1175/jcli-d-20-0629.1 public Journal of Climate, vol 34, iss 13 Southern Ocean Annular mode Wind stress Atmosphere-ocean interaction Extratropical cyclones Principal components analysis Atmospheric Sciences Oceanography Geomatic Engineering Meteorology & Atmospheric Sciences article 2021 ftcdlib https://doi.org/10.1175/jcli-d-20-0629.1 2024-06-28T06:28:21Z AbstractSouthern Ocean (SO) surface winds are essential for ventilating the upper ocean by bringing heat and CO2 to the ocean interior. The relationships between mixed-layer ventilation, the Southern Annular Mode (SAM), and the storm tracks remain unclear because processes can be governed by short-term wind events as well as long-term means.In this study, observed time-varying 5-day probability density functions (PDFs) of ERA5 surface winds and stresses over the SO are used in a singular value decomposition to derive a linearly independent set of empirical basis functions. The first modes of wind (72% of the total wind variance) and stress (74% of the total stress variance) are highly correlated with a standard SAM index (r = 0.82) and reflect SAM’s role in driving cyclone intensity and, in turn, extreme westerly winds. This Joint PDFs of zonal and meridional wind show that southerly and less westerly winds associated with strong mixed-layer ventilation are more frequent during short and distinct negative SAM phases. The probability of these short-term events might be related to mid-latitude atmospheric circulation. The second mode describes seasonal changes in the wind variance (16% of the total variance) that are uncorrelated with the first mode.The analysis produces similar results when repeated using 5-day PDFs from a suite of scatterometer products. Differences between wind product PDFs resemble the first mode of the PDFs. Together, these results show a strong correlation between surface stress PDFs and the leading modes of atmospheric variability, suggesting that empirical modes can serve as a novel pathway for understanding differences and variability of surface stress PDFs. Article in Journal/Newspaper Southern Ocean University of California: eScholarship Journal of Climate 1 80 |
institution |
Open Polar |
collection |
University of California: eScholarship |
op_collection_id |
ftcdlib |
language |
unknown |
topic |
Southern Ocean Annular mode Wind stress Atmosphere-ocean interaction Extratropical cyclones Principal components analysis Atmospheric Sciences Oceanography Geomatic Engineering Meteorology & Atmospheric Sciences |
spellingShingle |
Southern Ocean Annular mode Wind stress Atmosphere-ocean interaction Extratropical cyclones Principal components analysis Atmospheric Sciences Oceanography Geomatic Engineering Meteorology & Atmospheric Sciences Hell, Momme C Cornuelle, Bruce D Gille, Sarah T Lutsko, Nicholas J Time-Varying Empirical Probability Densities of Southern Ocean Surface Winds: Linking the Leading Mode to SAM and QuantifyingWind Product Differences |
topic_facet |
Southern Ocean Annular mode Wind stress Atmosphere-ocean interaction Extratropical cyclones Principal components analysis Atmospheric Sciences Oceanography Geomatic Engineering Meteorology & Atmospheric Sciences |
description |
AbstractSouthern Ocean (SO) surface winds are essential for ventilating the upper ocean by bringing heat and CO2 to the ocean interior. The relationships between mixed-layer ventilation, the Southern Annular Mode (SAM), and the storm tracks remain unclear because processes can be governed by short-term wind events as well as long-term means.In this study, observed time-varying 5-day probability density functions (PDFs) of ERA5 surface winds and stresses over the SO are used in a singular value decomposition to derive a linearly independent set of empirical basis functions. The first modes of wind (72% of the total wind variance) and stress (74% of the total stress variance) are highly correlated with a standard SAM index (r = 0.82) and reflect SAM’s role in driving cyclone intensity and, in turn, extreme westerly winds. This Joint PDFs of zonal and meridional wind show that southerly and less westerly winds associated with strong mixed-layer ventilation are more frequent during short and distinct negative SAM phases. The probability of these short-term events might be related to mid-latitude atmospheric circulation. The second mode describes seasonal changes in the wind variance (16% of the total variance) that are uncorrelated with the first mode.The analysis produces similar results when repeated using 5-day PDFs from a suite of scatterometer products. Differences between wind product PDFs resemble the first mode of the PDFs. Together, these results show a strong correlation between surface stress PDFs and the leading modes of atmospheric variability, suggesting that empirical modes can serve as a novel pathway for understanding differences and variability of surface stress PDFs. |
format |
Article in Journal/Newspaper |
author |
Hell, Momme C Cornuelle, Bruce D Gille, Sarah T Lutsko, Nicholas J |
author_facet |
Hell, Momme C Cornuelle, Bruce D Gille, Sarah T Lutsko, Nicholas J |
author_sort |
Hell, Momme C |
title |
Time-Varying Empirical Probability Densities of Southern Ocean Surface Winds: Linking the Leading Mode to SAM and QuantifyingWind Product Differences |
title_short |
Time-Varying Empirical Probability Densities of Southern Ocean Surface Winds: Linking the Leading Mode to SAM and QuantifyingWind Product Differences |
title_full |
Time-Varying Empirical Probability Densities of Southern Ocean Surface Winds: Linking the Leading Mode to SAM and QuantifyingWind Product Differences |
title_fullStr |
Time-Varying Empirical Probability Densities of Southern Ocean Surface Winds: Linking the Leading Mode to SAM and QuantifyingWind Product Differences |
title_full_unstemmed |
Time-Varying Empirical Probability Densities of Southern Ocean Surface Winds: Linking the Leading Mode to SAM and QuantifyingWind Product Differences |
title_sort |
time-varying empirical probability densities of southern ocean surface winds: linking the leading mode to sam and quantifyingwind product differences |
publisher |
eScholarship, University of California |
publishDate |
2021 |
url |
https://escholarship.org/uc/item/8jf2z19v https://escholarship.org/content/qt8jf2z19v/qt8jf2z19v.pdf https://doi.org/10.1175/jcli-d-20-0629.1 |
op_coverage |
1 - 80 |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_source |
Journal of Climate, vol 34, iss 13 |
op_relation |
qt8jf2z19v https://escholarship.org/uc/item/8jf2z19v https://escholarship.org/content/qt8jf2z19v/qt8jf2z19v.pdf doi:10.1175/jcli-d-20-0629.1 |
op_rights |
public |
op_doi |
https://doi.org/10.1175/jcli-d-20-0629.1 |
container_title |
Journal of Climate |
container_start_page |
1 |
op_container_end_page |
80 |
_version_ |
1810481472653492224 |