Climatic change and quasi-oscillations in central-west Argentina summer precipitation: Main features and coherent behaviour with southern African region

Summer rainfall variability (October to March) shows inter-annual to multi-decadal fluctuations over a vast area of subtropical Argentina between 28°S-38°S and 65°W-70°W. Statistically significant oscillations of quasi-period in the bands of 18-21, 6, 4 and 2 years can be found throughout the region...

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Autores principales:	Compagnucci, Rosa Hilda, Vargas, Walter Mario
Publicado:	2002
Materias:	annual variation climate change decadal variation precipitation (climatology) sea surface temperature summer teleconnection Africa Argentina
Acceso en línea:	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_09307575_v18_n5_p421_Compagnucci http://hdl.handle.net/20.500.12110/paper_09307575_v18_n5_p421_Compagnucci
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	paper:paper_09307575_v18_n5_p421_Compagnucci
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spelling	paper:paper_09307575_v18_n5_p421_Compagnucci2023-06-08T15:52:35Z Climatic change and quasi-oscillations in central-west Argentina summer precipitation: Main features and coherent behaviour with southern African region Compagnucci, Rosa Hilda Vargas, Walter Mario annual variation climate change decadal variation precipitation (climatology) sea surface temperature summer teleconnection Africa Argentina Summer rainfall variability (October to March) shows inter-annual to multi-decadal fluctuations over a vast area of subtropical Argentina between 28°S-38°S and 65°W-70°W. Statistically significant oscillations of quasi-period in the bands of 18-21, 6, 4 and 2 years can be found throughout the region and intra-regionally, though the latter are variable. The lower frequency variation produces alternating episodes of above and below normal rainfall each lasting roughly 9 years. This quasi-fluctuation appears to be shared with the summer rainfall region of South Africa and were in-phase related one another until mid-1970s. The teleconnection between both subtropical regions could be generated by an atmospheric-oceanic bridge through the global sea surface temperatures (SSTs), particularly those of the equatorial-tropical South Atlantic. From mid-1970s, the alternating wet and dry pattern has been interrupted in the Argentine region producing the longest, as yet unfinished, wet spell of the century. Thus, a significant change of the long-term variation was observed around 1977 toward lower frequencies. Since then the statistical model that explains more than 89% of the variance of the series until 1977, diverges from the observed values in the 1980s and 1990s. In addition the Yamamoto statistical index, employed to detect a climatic jump, reaches its major value in 1973 at the beginning of the current long wet spell. Therefore the change could be located between 1973 and 1977. Application of the t-student's test gives significant differences of mean values for pre-1977 and post-1977 sub-sample from both individual time series and the regional index series. The spectral analysis also shows changes in energy bands in concordance with the features of the change that occurred from mid-1970s. The change gives rise to a significant increment of more than 20% in average of normal rainfall over the region. Conversely, a drought between mid-1980s and the 1990s has been observed in the South Africa counterpart with severe characteristics, thereby continuing the quasi-18-year oscillation. Consequently, the low-frequency coherent behaviour between both the Argentine and South Africa regions is lost from the mid-1970s. The analysis of association of wet/dry spells and warm/cold, El Nino/La Nina episodes appears to be not significant at scales of year-to-year variability although at decadal to multi-decadal scales the association could be relevant. More than one process of multi-decadal variability of global SSTs could influence the Argentine summer rainfall region and the former bidecadal teleconnection. Finally, potential hypothetical factors of change are discussed, such as the strengthening of direct and indirect mechanisms of moisture flux transport associated with global warning, low-level atmospheric circulation changes and/or to SSTs mean condition long-term variations over tropical and sub-tropical South Atlantic and South Pacific oceans. Fil:Compagnucci, R.H. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Vargas, W.M. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2002 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_09307575_v18_n5_p421_Compagnucci http://hdl.handle.net/20.500.12110/paper_09307575_v18_n5_p421_Compagnucci
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic	annual variation climate change decadal variation precipitation (climatology) sea surface temperature summer teleconnection Africa Argentina
spellingShingle	annual variation climate change decadal variation precipitation (climatology) sea surface temperature summer teleconnection Africa Argentina Compagnucci, Rosa Hilda Vargas, Walter Mario Climatic change and quasi-oscillations in central-west Argentina summer precipitation: Main features and coherent behaviour with southern African region
topic_facet	annual variation climate change decadal variation precipitation (climatology) sea surface temperature summer teleconnection Africa Argentina
description	Summer rainfall variability (October to March) shows inter-annual to multi-decadal fluctuations over a vast area of subtropical Argentina between 28°S-38°S and 65°W-70°W. Statistically significant oscillations of quasi-period in the bands of 18-21, 6, 4 and 2 years can be found throughout the region and intra-regionally, though the latter are variable. The lower frequency variation produces alternating episodes of above and below normal rainfall each lasting roughly 9 years. This quasi-fluctuation appears to be shared with the summer rainfall region of South Africa and were in-phase related one another until mid-1970s. The teleconnection between both subtropical regions could be generated by an atmospheric-oceanic bridge through the global sea surface temperatures (SSTs), particularly those of the equatorial-tropical South Atlantic. From mid-1970s, the alternating wet and dry pattern has been interrupted in the Argentine region producing the longest, as yet unfinished, wet spell of the century. Thus, a significant change of the long-term variation was observed around 1977 toward lower frequencies. Since then the statistical model that explains more than 89% of the variance of the series until 1977, diverges from the observed values in the 1980s and 1990s. In addition the Yamamoto statistical index, employed to detect a climatic jump, reaches its major value in 1973 at the beginning of the current long wet spell. Therefore the change could be located between 1973 and 1977. Application of the t-student's test gives significant differences of mean values for pre-1977 and post-1977 sub-sample from both individual time series and the regional index series. The spectral analysis also shows changes in energy bands in concordance with the features of the change that occurred from mid-1970s. The change gives rise to a significant increment of more than 20% in average of normal rainfall over the region. Conversely, a drought between mid-1980s and the 1990s has been observed in the South Africa counterpart with severe characteristics, thereby continuing the quasi-18-year oscillation. Consequently, the low-frequency coherent behaviour between both the Argentine and South Africa regions is lost from the mid-1970s. The analysis of association of wet/dry spells and warm/cold, El Nino/La Nina episodes appears to be not significant at scales of year-to-year variability although at decadal to multi-decadal scales the association could be relevant. More than one process of multi-decadal variability of global SSTs could influence the Argentine summer rainfall region and the former bidecadal teleconnection. Finally, potential hypothetical factors of change are discussed, such as the strengthening of direct and indirect mechanisms of moisture flux transport associated with global warning, low-level atmospheric circulation changes and/or to SSTs mean condition long-term variations over tropical and sub-tropical South Atlantic and South Pacific oceans.
author	Compagnucci, Rosa Hilda Vargas, Walter Mario
author_facet	Compagnucci, Rosa Hilda Vargas, Walter Mario
author_sort	Compagnucci, Rosa Hilda
title	Climatic change and quasi-oscillations in central-west Argentina summer precipitation: Main features and coherent behaviour with southern African region
title_short	Climatic change and quasi-oscillations in central-west Argentina summer precipitation: Main features and coherent behaviour with southern African region
title_full	Climatic change and quasi-oscillations in central-west Argentina summer precipitation: Main features and coherent behaviour with southern African region
title_fullStr	Climatic change and quasi-oscillations in central-west Argentina summer precipitation: Main features and coherent behaviour with southern African region
title_full_unstemmed	Climatic change and quasi-oscillations in central-west Argentina summer precipitation: Main features and coherent behaviour with southern African region
title_sort	climatic change and quasi-oscillations in central-west argentina summer precipitation: main features and coherent behaviour with southern african region
publishDate	2002
url	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_09307575_v18_n5_p421_Compagnucci http://hdl.handle.net/20.500.12110/paper_09307575_v18_n5_p421_Compagnucci
work_keys_str_mv	AT compagnuccirosahilda climaticchangeandquasioscillationsincentralwestargentinasummerprecipitationmainfeaturesandcoherentbehaviourwithsouthernafricanregion AT vargaswaltermario climaticchangeandquasioscillationsincentralwestargentinasummerprecipitationmainfeaturesandcoherentbehaviourwithsouthernafricanregion
_version_	1768544419425812480

Climatic change and quasi-oscillations in central-west Argentina summer precipitation: Main features and coherent behaviour with southern African region

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