Weather regimes in the South American sector and neighbouring oceans during winter

We classified 34 years of winter daily 500 hPa geopotential height patterns over the eastern South Pacific-South America-South Atlantic region using the K-means clustering method. We found a significant classification into five weather regimes (WRs) defined as the most frequent large-scale circulati...

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Detalles Bibliográficos
Publicado: 2003
Materias:
atmospheric circulation
cluster analysis
regional climate
Southern Hemisphere
synoptic meteorology
winter
Atlantic Ocean
Pacific Ocean
South America
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_09307575_v21_n1_p91_Solman
http://hdl.handle.net/20.500.12110/paper_09307575_v21_n1_p91_Solman
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_09307575_v21_n1_p91_Solman
record_format dspace
spelling paper:paper_09307575_v21_n1_p91_Solman2023-06-08T15:52:35Z Weather regimes in the South American sector and neighbouring oceans during winter atmospheric circulation cluster analysis regional climate Southern Hemisphere synoptic meteorology winter Atlantic Ocean Pacific Ocean South America We classified 34 years of winter daily 500 hPa geopotential height patterns over the eastern South Pacific-South America-South Atlantic region using the K-means clustering method. We found a significant classification into five weather regimes (WRs) defined as the most frequent large-scale circulation anomalies: WR1 (trough centred downstream of the Drake Passage), WR2 (trough over the SW Pacific and ridge downstream), WR3 (ridge over the SE Pacific and NW-SE trough downstream), WR4 (trough over the SE Pacific and NW-SE ridge downstream) and WR5 (weak ridge to the west of southern South America). We also analysed their persistence and temporal evolution, including transitions between them and development around onsets and breaks of each regime. The preferred transitions, WR1 ← WR3 ← WR2 ← WR4 ← WR1 and also WR1 ← WR3 ← WR2 ← WR1, suggest the progression of a Rossby wave-like pattern in which each of the regimes resemble the Pacific-South America modes. Significant influence of the WRs on local climate over Argentina was found. The preferred transitions WR1 ← WR3 and WR3 ← WR2 induce sustained cold conditions over Patagonia and over northern Argentina, respectively. The most significant change in precipitation frequency is found for WR3, with wetter conditions over all the analysed regions. Finally, the interannual to interdecadal significant variations in the occurrence of these regimes were discussed. WR1 and WR3 are more frequent and WR2 is less frequent during El Niño, and WR2 and WR5 are more frequent and WR1 is less frequent during La Niña. A significant decrease in WR2 and increase of WR4 and WR5 during the 1970s and early 1980s were found. 2003 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_09307575_v21_n1_p91_Solman http://hdl.handle.net/20.500.12110/paper_09307575_v21_n1_p91_Solman
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic atmospheric circulation
cluster analysis
regional climate
Southern Hemisphere
synoptic meteorology
winter
Atlantic Ocean
Pacific Ocean
South America
spellingShingle atmospheric circulation
cluster analysis
regional climate
Southern Hemisphere
synoptic meteorology
winter
Atlantic Ocean
Pacific Ocean
South America
Weather regimes in the South American sector and neighbouring oceans during winter
topic_facet atmospheric circulation
cluster analysis
regional climate
Southern Hemisphere
synoptic meteorology
winter
Atlantic Ocean
Pacific Ocean
South America
description We classified 34 years of winter daily 500 hPa geopotential height patterns over the eastern South Pacific-South America-South Atlantic region using the K-means clustering method. We found a significant classification into five weather regimes (WRs) defined as the most frequent large-scale circulation anomalies: WR1 (trough centred downstream of the Drake Passage), WR2 (trough over the SW Pacific and ridge downstream), WR3 (ridge over the SE Pacific and NW-SE trough downstream), WR4 (trough over the SE Pacific and NW-SE ridge downstream) and WR5 (weak ridge to the west of southern South America). We also analysed their persistence and temporal evolution, including transitions between them and development around onsets and breaks of each regime. The preferred transitions, WR1 ← WR3 ← WR2 ← WR4 ← WR1 and also WR1 ← WR3 ← WR2 ← WR1, suggest the progression of a Rossby wave-like pattern in which each of the regimes resemble the Pacific-South America modes. Significant influence of the WRs on local climate over Argentina was found. The preferred transitions WR1 ← WR3 and WR3 ← WR2 induce sustained cold conditions over Patagonia and over northern Argentina, respectively. The most significant change in precipitation frequency is found for WR3, with wetter conditions over all the analysed regions. Finally, the interannual to interdecadal significant variations in the occurrence of these regimes were discussed. WR1 and WR3 are more frequent and WR2 is less frequent during El Niño, and WR2 and WR5 are more frequent and WR1 is less frequent during La Niña. A significant decrease in WR2 and increase of WR4 and WR5 during the 1970s and early 1980s were found.
title Weather regimes in the South American sector and neighbouring oceans during winter
title_short Weather regimes in the South American sector and neighbouring oceans during winter
title_full Weather regimes in the South American sector and neighbouring oceans during winter
title_fullStr Weather regimes in the South American sector and neighbouring oceans during winter
title_full_unstemmed Weather regimes in the South American sector and neighbouring oceans during winter
title_sort weather regimes in the south american sector and neighbouring oceans during winter
publishDate 2003
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_09307575_v21_n1_p91_Solman
http://hdl.handle.net/20.500.12110/paper_09307575_v21_n1_p91_Solman
_version_ 1768543759479341056

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