Sensitivity of the surface orographic gravity wave drag to vertical wind shear over Antarctica
The effects of vertical wind shear on orographic gravity wave drag derived previously from inviscid linear theory are evaluated using reanalysis data. Emphasis is placed on the relative importance of uniform and directional shear (associated with first and second vertical derivatives of the wind vel...
Published in: | Quarterly Journal of the Royal Meteorological Society |
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crwiley:10.1002/qj.3416 2024-06-02T07:57:24+00:00 Sensitivity of the surface orographic gravity wave drag to vertical wind shear over Antarctica Turner, Holly V. Teixeira, Miguel A. C. Methven, John Vosper, Simon B. Natural Environment Research Council 2018 http://dx.doi.org/10.1002/qj.3416 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fqj.3416 https://onlinelibrary.wiley.com/doi/pdf/10.1002/qj.3416 https://onlinelibrary.wiley.com/doi/full-xml/10.1002/qj.3416 https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.3416 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Quarterly Journal of the Royal Meteorological Society volume 145, issue 718, page 164-178 ISSN 0035-9009 1477-870X journal-article 2018 crwiley https://doi.org/10.1002/qj.3416 2024-05-03T10:42:19Z The effects of vertical wind shear on orographic gravity wave drag derived previously from inviscid linear theory are evaluated using reanalysis data. Emphasis is placed on the relative importance of uniform and directional shear (associated with first and second vertical derivatives of the wind velocity), which are theoretically predicted, respectively, to reduce and enhance the surface drag. Two levels at which the wind derivatives are estimated are considered for evaluating the shear corrections to the drag: a height just above the parametrized boundary‐layer height (BLH) in the ECMWF model, and a height of order the standard deviation of the subgrid‐scale orography elevation (SDH), adopted by previous authors. A climatology of the Richardson number ( Ri ) computed for the decade 2006–2015 suggests that the Antarctic region has a high incidence of low Ri values, implying high shear conditions. Shear estimated at the BLH has a relatively modest impact on the drag, whereas shear estimated at the SDH has a stronger impact. Predicted drag enhancement is more widespread than drag reduction because terms involving second wind derivatives dominate the drag correction for a larger fraction of the time than terms involving first derivatives. A comparison of climatologies of the drag corrections for horizontally elliptical mountains (which represent anisotropic subgrid‐scale orography in parametrizations) and axisymmetric mountains always results in drag enhancement over Antarctica, with a maximum during the JJA season, showing qualitative robustness to both calculation height and orography anisotropy. However, this enhancement is smaller when using elliptical instead of axisymmetric orography. This is because the shear vector is predominantly oriented along mountain ridges rather than across them when the orography is anisotropic. Article in Journal/Newspaper Antarc* Antarctic Antarctica Wiley Online Library Antarctic The Antarctic Quarterly Journal of the Royal Meteorological Society 145 718 164 178 |
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Wiley Online Library |
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crwiley |
language |
English |
description |
The effects of vertical wind shear on orographic gravity wave drag derived previously from inviscid linear theory are evaluated using reanalysis data. Emphasis is placed on the relative importance of uniform and directional shear (associated with first and second vertical derivatives of the wind velocity), which are theoretically predicted, respectively, to reduce and enhance the surface drag. Two levels at which the wind derivatives are estimated are considered for evaluating the shear corrections to the drag: a height just above the parametrized boundary‐layer height (BLH) in the ECMWF model, and a height of order the standard deviation of the subgrid‐scale orography elevation (SDH), adopted by previous authors. A climatology of the Richardson number ( Ri ) computed for the decade 2006–2015 suggests that the Antarctic region has a high incidence of low Ri values, implying high shear conditions. Shear estimated at the BLH has a relatively modest impact on the drag, whereas shear estimated at the SDH has a stronger impact. Predicted drag enhancement is more widespread than drag reduction because terms involving second wind derivatives dominate the drag correction for a larger fraction of the time than terms involving first derivatives. A comparison of climatologies of the drag corrections for horizontally elliptical mountains (which represent anisotropic subgrid‐scale orography in parametrizations) and axisymmetric mountains always results in drag enhancement over Antarctica, with a maximum during the JJA season, showing qualitative robustness to both calculation height and orography anisotropy. However, this enhancement is smaller when using elliptical instead of axisymmetric orography. This is because the shear vector is predominantly oriented along mountain ridges rather than across them when the orography is anisotropic. |
author2 |
Natural Environment Research Council |
format |
Article in Journal/Newspaper |
author |
Turner, Holly V. Teixeira, Miguel A. C. Methven, John Vosper, Simon B. |
spellingShingle |
Turner, Holly V. Teixeira, Miguel A. C. Methven, John Vosper, Simon B. Sensitivity of the surface orographic gravity wave drag to vertical wind shear over Antarctica |
author_facet |
Turner, Holly V. Teixeira, Miguel A. C. Methven, John Vosper, Simon B. |
author_sort |
Turner, Holly V. |
title |
Sensitivity of the surface orographic gravity wave drag to vertical wind shear over Antarctica |
title_short |
Sensitivity of the surface orographic gravity wave drag to vertical wind shear over Antarctica |
title_full |
Sensitivity of the surface orographic gravity wave drag to vertical wind shear over Antarctica |
title_fullStr |
Sensitivity of the surface orographic gravity wave drag to vertical wind shear over Antarctica |
title_full_unstemmed |
Sensitivity of the surface orographic gravity wave drag to vertical wind shear over Antarctica |
title_sort |
sensitivity of the surface orographic gravity wave drag to vertical wind shear over antarctica |
publisher |
Wiley |
publishDate |
2018 |
url |
http://dx.doi.org/10.1002/qj.3416 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fqj.3416 https://onlinelibrary.wiley.com/doi/pdf/10.1002/qj.3416 https://onlinelibrary.wiley.com/doi/full-xml/10.1002/qj.3416 https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.3416 |
geographic |
Antarctic The Antarctic |
geographic_facet |
Antarctic The Antarctic |
genre |
Antarc* Antarctic Antarctica |
genre_facet |
Antarc* Antarctic Antarctica |
op_source |
Quarterly Journal of the Royal Meteorological Society volume 145, issue 718, page 164-178 ISSN 0035-9009 1477-870X |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1002/qj.3416 |
container_title |
Quarterly Journal of the Royal Meteorological Society |
container_volume |
145 |
container_issue |
718 |
container_start_page |
164 |
op_container_end_page |
178 |
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1800740559830122496 |