The role of large‐scale eddies in the occurrence of winter precipitation deficits in Portugal
Abstract The severest winter precipitation deficits in Portugal result from an enhancement in the stationary wave pattern of the atmospheric large‐scale circulation over the Northern Hemisphere, which implies a strengthening of the axially asymmetric eddies, mainly over the North Atlantic and adjace...
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crwiley:10.1002/joc.1818 2024-06-02T08:11:09+00:00 The role of large‐scale eddies in the occurrence of winter precipitation deficits in Portugal Santos, J. A. Andrade, C. Corte‐Real, J. Leite, S. 2008 http://dx.doi.org/10.1002/joc.1818 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjoc.1818 https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/joc.1818 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor International Journal of Climatology volume 29, issue 10, page 1493-1507 ISSN 0899-8418 1097-0088 journal-article 2008 crwiley https://doi.org/10.1002/joc.1818 2024-05-03T11:26:06Z Abstract The severest winter precipitation deficits in Portugal result from an enhancement in the stationary wave pattern of the atmospheric large‐scale circulation over the Northern Hemisphere, which implies a strengthening of the axially asymmetric eddies, mainly over the North Atlantic and adjacent continental areas. This enhancement leads to a strong warm‐core ridge westward of Iberia, with a nearly equivalent barotropic structure, and a clear separation between the subtropical and polar‐front jet. These atmospheric conditions are clearly unfavourable to the establishment of rain‐generating mechanisms over Portugal, leading to a lack of precipitation and to extremely dry conditions with a high potential to trigger drought episodes. Conversely, the atmospheric flow during extremely wet winters contrasts highly with the above‐described conditions by presenting a significantly weakened North Atlantic ridge and a relatively unclear separation between the two westerly jets. A diagnosis of the main forcing dynamical mechanisms that generate and maintain the anomalous flow is carried out in two ways: by analyzing the Eliassen–Palm fluxes, zonally averaged over a North Atlantic window, and by calculating the third and sixth components of the empirical forcing functions. The former approach enables a quantification of the contributions made by the transient and stationary‐eddy transports of enthalpy and momentum to the establishment of the contrasting dynamical structures. The latter approach explores the role of local transient transports of enthalpy and angular momentum in forcing large‐scale asymmetries. Copyright © 2008 Royal Meteorological Society Article in Journal/Newspaper North Atlantic Wiley Online Library International Journal of Climatology 29 10 1493 1507 |
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Wiley Online Library |
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language |
English |
description |
Abstract The severest winter precipitation deficits in Portugal result from an enhancement in the stationary wave pattern of the atmospheric large‐scale circulation over the Northern Hemisphere, which implies a strengthening of the axially asymmetric eddies, mainly over the North Atlantic and adjacent continental areas. This enhancement leads to a strong warm‐core ridge westward of Iberia, with a nearly equivalent barotropic structure, and a clear separation between the subtropical and polar‐front jet. These atmospheric conditions are clearly unfavourable to the establishment of rain‐generating mechanisms over Portugal, leading to a lack of precipitation and to extremely dry conditions with a high potential to trigger drought episodes. Conversely, the atmospheric flow during extremely wet winters contrasts highly with the above‐described conditions by presenting a significantly weakened North Atlantic ridge and a relatively unclear separation between the two westerly jets. A diagnosis of the main forcing dynamical mechanisms that generate and maintain the anomalous flow is carried out in two ways: by analyzing the Eliassen–Palm fluxes, zonally averaged over a North Atlantic window, and by calculating the third and sixth components of the empirical forcing functions. The former approach enables a quantification of the contributions made by the transient and stationary‐eddy transports of enthalpy and momentum to the establishment of the contrasting dynamical structures. The latter approach explores the role of local transient transports of enthalpy and angular momentum in forcing large‐scale asymmetries. Copyright © 2008 Royal Meteorological Society |
format |
Article in Journal/Newspaper |
author |
Santos, J. A. Andrade, C. Corte‐Real, J. Leite, S. |
spellingShingle |
Santos, J. A. Andrade, C. Corte‐Real, J. Leite, S. The role of large‐scale eddies in the occurrence of winter precipitation deficits in Portugal |
author_facet |
Santos, J. A. Andrade, C. Corte‐Real, J. Leite, S. |
author_sort |
Santos, J. A. |
title |
The role of large‐scale eddies in the occurrence of winter precipitation deficits in Portugal |
title_short |
The role of large‐scale eddies in the occurrence of winter precipitation deficits in Portugal |
title_full |
The role of large‐scale eddies in the occurrence of winter precipitation deficits in Portugal |
title_fullStr |
The role of large‐scale eddies in the occurrence of winter precipitation deficits in Portugal |
title_full_unstemmed |
The role of large‐scale eddies in the occurrence of winter precipitation deficits in Portugal |
title_sort |
role of large‐scale eddies in the occurrence of winter precipitation deficits in portugal |
publisher |
Wiley |
publishDate |
2008 |
url |
http://dx.doi.org/10.1002/joc.1818 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjoc.1818 https://rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/joc.1818 |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
International Journal of Climatology volume 29, issue 10, page 1493-1507 ISSN 0899-8418 1097-0088 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.1002/joc.1818 |
container_title |
International Journal of Climatology |
container_volume |
29 |
container_issue |
10 |
container_start_page |
1493 |
op_container_end_page |
1507 |
_version_ |
1800757197425082368 |