Channelling of high-latitude boundary-layer flow
International audience Due to the stability of the boundary-layer stratification, high-latitude winds over complex terrain are strongly affected by blocking and channelling effects. Consequently, at many low-lying communities in the Canadian Archipelago, including Cape Dorset and Iqaluit considered...
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ftinsu:oai:HAL:hal-00302952v1 2023-11-12T04:15:35+01:00 Channelling of high-latitude boundary-layer flow Nawri, N. Stewart, R. E. Department of Atmospheric and Oceanic Sciences Montréal McGill University = Université McGill Montréal, Canada 2008-01-31 https://hal.science/hal-00302952 https://hal.science/hal-00302952/document https://hal.science/hal-00302952/file/npg-15-33-2008.pdf en eng HAL CCSD European Geosciences Union (EGU) hal-00302952 https://hal.science/hal-00302952 https://hal.science/hal-00302952/document https://hal.science/hal-00302952/file/npg-15-33-2008.pdf info:eu-repo/semantics/OpenAccess ISSN: 1023-5809 EISSN: 1607-7946 Nonlinear Processes in Geophysics https://hal.science/hal-00302952 Nonlinear Processes in Geophysics, 2008, 15 (1), pp.33-52 [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO] [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] [SDU.STU]Sciences of the Universe [physics]/Earth Sciences info:eu-repo/semantics/article Journal articles 2008 ftinsu 2023-10-25T16:26:26Z International audience Due to the stability of the boundary-layer stratification, high-latitude winds over complex terrain are strongly affected by blocking and channelling effects. Consequently, at many low-lying communities in the Canadian Archipelago, including Cape Dorset and Iqaluit considered in this study, surface winds for the most part are from two diametrically opposed directions, following the orientation of the elevated terrain. Shifts between the two prevailing wind directions can be sudden and are associated with geostrophic wind directions within a well defined narrow range. To quantitatively investigate the role of large-scale pressure gradients and the quasi-geostrophic overlying flow, an idealised dynamical system for the evolution of channelled surface winds is derived from the basic equations of motion, in which stability of stationary along-channel wind directions is described as a function of the geostrophic wind. In comparison with long-term horizontal wind statistics at the two locations it is shown that the climatologically prevailing wind directions can be identified as stationary states of the idealised wind model, and that shifts between prevailing wind directions can be represented as stability transitions between these stationary states. In that sense, the prevailing local wind conditions can be interpreted as attracting states of the actual flow, with observed surface winds adjusting to a new stable direction as determined by the idealised system within 3?9 h. Over these time-scales and longer it is therefore advantageous to determine the relatively slow evolution of the observationally well-resolved large-scale pressure distribution, instead of modelling highly variable surface winds directly. The simplified model also offers a tool for dynamical downscaling of global climate simulations, and for determining future scenarios for local prevailing wind conditions. In particular, it allows an estimation of the sensitivity of local low-level winds to changes in the large-scale ... Article in Journal/Newspaper Canadian Archipelago Cape Dorset Iqaluit Institut national des sciences de l'Univers: HAL-INSU Cape Dorset ENVELOPE(-76.482,-76.482,64.179,64.179) |
institution |
Open Polar |
collection |
Institut national des sciences de l'Univers: HAL-INSU |
op_collection_id |
ftinsu |
language |
English |
topic |
[PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO] [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
spellingShingle |
[PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO] [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] [SDU.STU]Sciences of the Universe [physics]/Earth Sciences Nawri, N. Stewart, R. E. Channelling of high-latitude boundary-layer flow |
topic_facet |
[PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO] [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph] [SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
description |
International audience Due to the stability of the boundary-layer stratification, high-latitude winds over complex terrain are strongly affected by blocking and channelling effects. Consequently, at many low-lying communities in the Canadian Archipelago, including Cape Dorset and Iqaluit considered in this study, surface winds for the most part are from two diametrically opposed directions, following the orientation of the elevated terrain. Shifts between the two prevailing wind directions can be sudden and are associated with geostrophic wind directions within a well defined narrow range. To quantitatively investigate the role of large-scale pressure gradients and the quasi-geostrophic overlying flow, an idealised dynamical system for the evolution of channelled surface winds is derived from the basic equations of motion, in which stability of stationary along-channel wind directions is described as a function of the geostrophic wind. In comparison with long-term horizontal wind statistics at the two locations it is shown that the climatologically prevailing wind directions can be identified as stationary states of the idealised wind model, and that shifts between prevailing wind directions can be represented as stability transitions between these stationary states. In that sense, the prevailing local wind conditions can be interpreted as attracting states of the actual flow, with observed surface winds adjusting to a new stable direction as determined by the idealised system within 3?9 h. Over these time-scales and longer it is therefore advantageous to determine the relatively slow evolution of the observationally well-resolved large-scale pressure distribution, instead of modelling highly variable surface winds directly. The simplified model also offers a tool for dynamical downscaling of global climate simulations, and for determining future scenarios for local prevailing wind conditions. In particular, it allows an estimation of the sensitivity of local low-level winds to changes in the large-scale ... |
author2 |
Department of Atmospheric and Oceanic Sciences Montréal McGill University = Université McGill Montréal, Canada |
format |
Article in Journal/Newspaper |
author |
Nawri, N. Stewart, R. E. |
author_facet |
Nawri, N. Stewart, R. E. |
author_sort |
Nawri, N. |
title |
Channelling of high-latitude boundary-layer flow |
title_short |
Channelling of high-latitude boundary-layer flow |
title_full |
Channelling of high-latitude boundary-layer flow |
title_fullStr |
Channelling of high-latitude boundary-layer flow |
title_full_unstemmed |
Channelling of high-latitude boundary-layer flow |
title_sort |
channelling of high-latitude boundary-layer flow |
publisher |
HAL CCSD |
publishDate |
2008 |
url |
https://hal.science/hal-00302952 https://hal.science/hal-00302952/document https://hal.science/hal-00302952/file/npg-15-33-2008.pdf |
long_lat |
ENVELOPE(-76.482,-76.482,64.179,64.179) |
geographic |
Cape Dorset |
geographic_facet |
Cape Dorset |
genre |
Canadian Archipelago Cape Dorset Iqaluit |
genre_facet |
Canadian Archipelago Cape Dorset Iqaluit |
op_source |
ISSN: 1023-5809 EISSN: 1607-7946 Nonlinear Processes in Geophysics https://hal.science/hal-00302952 Nonlinear Processes in Geophysics, 2008, 15 (1), pp.33-52 |
op_relation |
hal-00302952 https://hal.science/hal-00302952 https://hal.science/hal-00302952/document https://hal.science/hal-00302952/file/npg-15-33-2008.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1782332843935924224 |