Intraseasonal variability in South America during the cold season

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Intraseasonal (IS) variability in South America is analyzed during the cold season using 10-90 day bandpass filtered OLR anomalies (FOLR). IS variability explains a large percentage of variance with maximum values over Paraguay, northeastern Argentina, and southern Brazil. The leading pattern of FOL...

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Autores principales: Alvarez, M.S., Vera, C.S., Kiladis, G.N., Liebmann, B.
Formato: INPR
Lenguaje:English
Materias:
Intraseasonal variability
Outgoing longwave radiation
South America
Winter
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_09307575_v_n_p1_Alvarez
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_09307575_v_n_p1_Alvarez2023-10-03T15:48:07Z Intraseasonal variability in South America during the cold season Alvarez, M.S. Vera, C.S. Kiladis, G.N. Liebmann, B. Intraseasonal variability Outgoing longwave radiation South America Winter Intraseasonal (IS) variability in South America is analyzed during the cold season using 10-90 day bandpass filtered OLR anomalies (FOLR). IS variability explains a large percentage of variance with maximum values over Paraguay, northeastern Argentina, and southern Brazil. The leading pattern of FOLR, as isolated from an EOF analysis, (Cold Season IS pattern, CSIS), is characterized by a monopole centered over southeastern South America (SESA) with a northwest-southeast orientation. CSIS induces a large modulation on daily precipitation anomalies, especially on both wet spells and daily precipitation extremes, which are favored during positive (wet) CSIS phases. Large-Scale OLR anomalies over the tropical Indian and west Pacific Oceans associated with CSIS exhibit eastward propagation along tropical latitudes. In addition, circulation anomalies in the Southern Hemisphere reveal the presence of an anticyclonic anomaly over Antarctica with opposite-sign anomalies in middle latitudes 10 days before CSIS is maximum as well as evidence of Rossby wave-like patterns. Positive precipitation anomalies in SESA are favored during wet CSIS phases by the intensification of a cyclonic anomaly located further south, which is discernible over the southeastern Pacific for at least 14 days before CSIS peaks. The cyclonic anomaly evolution is accompanied by the intensification of an upstream anticyclonic anomaly, which remains quasi-stationary near the Antarctica Peninsula before the CSIS peak. We speculate that the stationary behavior of the anticyclonic center is favored by a hemispheric circulation anomaly pattern resembling that associated with a negative southern annular mode phase and a wavenumber 3-4 pattern at middle latitudes. © 2013 Springer-Verlag Berlin Heidelberg. Fil:Alvarez, M.S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Vera, C.S. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. INPR English info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_09307575_v_n_p1_Alvarez
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
language English
orig_language_str_mv English
topic Intraseasonal variability
Outgoing longwave radiation
South America
Winter
spellingShingle Intraseasonal variability
Outgoing longwave radiation
South America
Winter
Alvarez, M.S.
Vera, C.S.
Kiladis, G.N.
Liebmann, B.
Intraseasonal variability in South America during the cold season
topic_facet Intraseasonal variability
Outgoing longwave radiation
South America
Winter
description Intraseasonal (IS) variability in South America is analyzed during the cold season using 10-90 day bandpass filtered OLR anomalies (FOLR). IS variability explains a large percentage of variance with maximum values over Paraguay, northeastern Argentina, and southern Brazil. The leading pattern of FOLR, as isolated from an EOF analysis, (Cold Season IS pattern, CSIS), is characterized by a monopole centered over southeastern South America (SESA) with a northwest-southeast orientation. CSIS induces a large modulation on daily precipitation anomalies, especially on both wet spells and daily precipitation extremes, which are favored during positive (wet) CSIS phases. Large-Scale OLR anomalies over the tropical Indian and west Pacific Oceans associated with CSIS exhibit eastward propagation along tropical latitudes. In addition, circulation anomalies in the Southern Hemisphere reveal the presence of an anticyclonic anomaly over Antarctica with opposite-sign anomalies in middle latitudes 10 days before CSIS is maximum as well as evidence of Rossby wave-like patterns. Positive precipitation anomalies in SESA are favored during wet CSIS phases by the intensification of a cyclonic anomaly located further south, which is discernible over the southeastern Pacific for at least 14 days before CSIS peaks. The cyclonic anomaly evolution is accompanied by the intensification of an upstream anticyclonic anomaly, which remains quasi-stationary near the Antarctica Peninsula before the CSIS peak. We speculate that the stationary behavior of the anticyclonic center is favored by a hemispheric circulation anomaly pattern resembling that associated with a negative southern annular mode phase and a wavenumber 3-4 pattern at middle latitudes. © 2013 Springer-Verlag Berlin Heidelberg.
format INPR
author Alvarez, M.S.
Vera, C.S.
Kiladis, G.N.
Liebmann, B.
author_facet Alvarez, M.S.
Vera, C.S.
Kiladis, G.N.
Liebmann, B.
author_sort Alvarez, M.S.
title Intraseasonal variability in South America during the cold season
title_short Intraseasonal variability in South America during the cold season
title_full Intraseasonal variability in South America during the cold season
title_fullStr Intraseasonal variability in South America during the cold season
title_full_unstemmed Intraseasonal variability in South America during the cold season
title_sort intraseasonal variability in south america during the cold season
url http://hdl.handle.net/20.500.12110/paper_09307575_v_n_p1_Alvarez
work_keys_str_mv AT alvarezms intraseasonalvariabilityinsouthamericaduringthecoldseason
AT veracs intraseasonalvariabilityinsouthamericaduringthecoldseason
AT kiladisgn intraseasonalvariabilityinsouthamericaduringthecoldseason
AT liebmannb intraseasonalvariabilityinsouthamericaduringthecoldseason
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