Low-frequency oscillations in climatic and hydrological variables in southern South America?s tropical-subtropical regions

Vargas, Walter M.; Minetti, Juan Leonidas; Poblete, Arnobio Germán

doi:10.1007/s007040200010

Cited by 24 publications

(18 citation statements)

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“…It does not appear as significant in the MTM spectra, however, due to the shortness of the record analyzed (40 years). This long‐term variation in the occurrence of CD in summer was also shown by Barrucand and Rusticucci [2001] and was observed in other variables such as annual flow of the Paraná River, rainfall in northeastern Argentina and humidity advection into the continent in southern South America [ Minetti and Vargas , 1999; Vargas et al , 2002]. A marked change of sign is clearly observed in the summer CD and WD time series (and those of their associated SST) around the second part of the 1970s (results not shown), which is presumably related to the well known climatic “jump” of 1976/1977 [ Deser and Blackmon , 1993; Kushnir , 1994].…”

Section: Temporal Variabilitysupporting

confidence: 75%

Warm and cold events in Argentina and their relationship with South Atlantic and South Pacific Sea surface temperatures

2003

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[1] A Singular Value Decomposition (SVD) analysis was performed jointly on extreme temperature events in Argentina and sea surface temperature (SST) in the South Atlantic and South Pacific. Sea level pressure (SLP) patterns associated with the first SVD coupled mode were also analyzed. Winter is the season of the year that is best represented by the first mode, accounting for up to 70% of the winter covariance between temperature events and SST. The warm and cold events in Argentina are essentially a consequence of the creation of meridional atmospheric circulations over the continent. Such atmospheric patterns result from displacements and intensity changes of the subtropical anticyclones over the oceans and of the continental low-pressure center in northwestern Argentina. The temperature events in southern Argentina are also closely related to the warming and cooling of the coastal waters in the South Atlantic and South Pacific. The analysis suggests that in summer and winter, high (low) occurrence of warm events and low (high) occurrence of cold events are related to similar oceanic and atmospheric circulation situations. The temperature events in Argentina show higher correlation with the Atlantic than with the Pacific, which reflects the importance of the ''orographic barrier'' of the Andes Mountains in driving the atmospheric circulation. The only exception to this rule concerns the warm events in spring, for which the warming of the equatorial Pacific (the ENSO pattern) appears as the dominant mode. The temporal patterns of the temperature events in Argentina exhibit significant interannual variability in fall, winter, and spring, with periods of 3 to 5 years. The summer patterns suggest a very low-frequency variation with a period longer than 20 years.

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Section: Temporal Variabilitysupporting

confidence: 75%

Warm and cold events in Argentina and their relationship with South Atlantic and South Pacific Sea surface temperatures

2003

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“…A 15-year component is highlighted in the Parana and Paraguay River discharges by Robertson and Mechoso (1998) with high river runoff related to anomalously cool SSTs over the tropical North Atlantic. Vargas et al (2002) described an interdecadal 22-26-year variability which may be related to the ENSO cycle modulation. Robertson et al (2001) examined a more complex combination of 2.5, 8 and 17-year processes in the Parana River and Krepper et al (2003) noted a combination of 3, 6 and 30-year variability in the Uruguay basin.…”

Section: Parana Discharge Variabilitymentioning

confidence: 98%

Recent advances in wavelet analyses: Part 2—Amazon, Parana, Orinoco and Congo discharges time scale variability

Labat

Ronchail

Guyot

2005

Journal of Hydrology

208

112

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“…En el espectro interanual Tucumán y Río Gallegos presentan oscilaciones significativas en períodos centrados en 12 años entre los años 1950-1970. Para la temperatura mínima los períodos de máxima energía son más heterogéneos donde solamente Río Gallegos muestra un patrón de oscilación pluridecadal (12-28 años) durante todo el período y la aparición de un máximo centrado en la banda de 6 y 12 años durante el período 1960-1985. Estos cambios de baja frecuencia concuerdan con los resultados obtenidos en distintas variables del sistema climático por Compagnucci y Vargas (1983) para las precipitaciones estivales del noroeste argentino, Minetti y Carletto (1990) y Vargas et al (2002), donde encuentran señales con períodos entre 17 y 26 años. Barrucand y Rusticucci (2001) detectan la presencia de ondas largas (mayores a 10 años) que dominan la variabilidad interanual de la frecuencia de días extremadamente fríos en el este del país (especialmente en verano), ondas medias (entre 3 y 10 años) en el centro y norte del país y ondas cortas (cuasi bienales, menores a 3 años) predominan en áreas costeras.…”

Section: Resultados Y Discusiónunclassified

Variabilidad de Baja Frecuencia de la Persistencia de la Temperatura en el Sudeste de Sudamérica

Naumann

Vargas

2017

Rev. bras. meteorol.

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Recebido em 21 de Abril de 2015 -Aceito em 3 de Junho de 2016 ResumenSe analizan las estructuras de las autocovarianzas y autocorrelaciones de las temperaturas máximas y mínimas en estaciones de referencia en el sudeste de Sudamérica. A través de estas propiedades se observa que existen oscilaciones de períodos entre 18 y 25 años en las series bajo estudio, aunque estas periodicidades presentan cambios con el tiempo, especialmente entre los años . La excepción es Río Gallegos donde la periodicidad de 18 años se observa durante todo el registro. La persistencia definida mediante el primer coeficiente de autocorrelación es función de la cantidad de términos de autocovarianza negativas. No obstante, durante algunos años es dependiente de la magnitud de los términos positivos dados por las irrupciones cálidas o frías intensas. Entre los años 1950 y 1970 se ha observado un aumento de la variabilidad con una alta alternancia entre períodos de mayor y menor persistencia. Estos cambios analizados en la persistencia sugieren una variación en la frecuencia de distintos tipos de circulación que tienen un impacto directo en la estructura térmica regional. Así mismo, variaciones de este tipo pueden tener serios impactos socio-económicos ya que estos afectarían directamente la frecuencia y duración de los eventos extremos. Esto tiene importancia también en el diseño de métodos de control y consistencia ya que en ellos es posible considerar como outlier o información errónea los cambios producidos por las irrupciones de escala sinóptica mencionadas anteriormente. Palabras-clave: variabilidad climática, memoria, temperatura diaria, análisis wavelet. Low-Frequency Variability of Surface Air Temperature Persistence in Southern South America AbstractEight reference stations in south-eastern South America are analysed to derive the auto-covariance and auto-correlations of maximum and minimum temperature. Through the analysis are observed oscillations of periods between 18 and 25 years in the series studied. These periodicities show changes over time, especially in the 1950-1970 period. The exception is Río Gallegos where a periodicity of 18 years is observed throughout the entire record. Persistence is defined as the first correlation coefficient and is a function of the number of negative terms in the auto-covariance. However for some years it is mainly driven by the magnitude of the positive terms given by extreme warm or cold outbreaks. Between 1950 and 1970 it was observed an increased variability in the analysed properties. These changes suggest a variation in the frequency of different circulation patterns having a direct impact on the regional thermal structure. Likewise, this kind of variations can have serious socio-economic impacts as these directly affect the frequency and duration of extreme events. This is relevant in the design of consistency and quality control methods to detect outliers or systematic errors.

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Low-frequency oscillations in climatic and hydrological variables in southern South America?s tropical-subtropical regions

Cited by 24 publications

References 0 publications

Warm and cold events in Argentina and their relationship with South Atlantic and South Pacific Sea surface temperatures

Warm and cold events in Argentina and their relationship with South Atlantic and South Pacific Sea surface temperatures

Recent advances in wavelet analyses: Part 2—Amazon, Parana, Orinoco and Congo discharges time scale variability

Variabilidad de Baja Frecuencia de la Persistencia de la Temperatura en el Sudeste de Sudamérica

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