Variability of South American Convective Cloud Systems and Tropospheric Circulation during January–March 1998 and 1999

Ferreira, Rosana Nieto; Rickenbach, Thomas M.; Herdies, Dirceu Luís; Carvalho, Leila M. V.

doi:10.1175/1520-0493(2003)131<0961:vosacc>2.0.co;2

Cited by 57 publications

(49 citation statements)

References 35 publications

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“…The dipole variability has been linked to anomalies in other outstanding climate features such as the intensity of the South Atlantic convergence zone (SACZ), South American low-level jet (SALLJ), Pacific-South American (PSA) modes, and El Niñ o-Southern Oscillation (ENSO). Several papers extensively document such links (e.g., Robertson and Mechoso 2000;Díaz and Aceituno 2003;Mo and Paegle 2001;Paegle and Mo 2002;Liebmann et al 2004;Ferreira et al 2003;Grimm 2003;Grimm et al 2007;Silva et al 2009). …”

Section: Introductionmentioning

confidence: 99%

Relationships between Upper-Level Circulation over South America and Rainfall over Southeastern South America: A Physical Base for Seasonal Predictions

2010

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The existence of a significant simultaneous correlation between bimonthly mean precipitation anomalies over southeastern South America (SESA) and either the first or the second (depending on season) leading mode of interannual variability of upper-level wind over South America (SA) is demonstrated during all seasons except winter. The pattern associated with these modes of variability is similar during all seasons and consists of a continental-scale vortex centered over the eastern coast of subtropical SA. The vortex has a quasi-barotropic structure during all seasons, and its variability modifies moisture transport from the South American low-level jet and the western tropical Atlantic to SESA thus creating precipitation anomalies in this region. During spring (October-November) and summer (January-February) the circulation creates a second center of precipitation anomalies over the South Atlantic convergence zone that are of opposite sign to those over SESA, while during fall (April-May) precipitation anomalies are primarily confined to SESA. On the basis of the correlation between upper-level winds and precipitation, an empirical method to produce longrange forecasts of bimonthly mean precipitation over SESA is developed. Method tests in hindcast mode for the period 1959-2001 show a potential for reliable predictions during the southern spring, summer, and fall. The method is further tested in an experimental mode by using Development of a European Multimodel Ensemble System for Seasonal-to-Interannual Prediction (DEMETER) wind hindcasts. Forecasts obtained in this way are skillful during spring only, with highest skill during El Niñ o-Southern Oscillation years. During summer and fall, the DEMETER forecasts of wind anomalies limit the method's ability to make reliable real predictions.

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Section: Introductionmentioning

confidence: 99%

Relationships between Upper-Level Circulation over South America and Rainfall over Southeastern South America: A Physical Base for Seasonal Predictions

2010

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“…One of these systems is the Low Level Jet east of the Andes or the South American Low Level Jet (SALLJ) defined as a subsynoptic system of wind with high speed, with maximum velocity around 2 km height, horizontal extension of hundreds of kilometers and that occurs in all seasons (e.g., Stensrud, 1996;Douglas et al, 2000;Marengo et al, 2004;Misra et al, 2000;Berbery and Barros, 2002). This system seems to be responsible for transporting large quantiCorrespondence to: G. A. M. Silva (gyrlene@model.iag.usp.br) ties of water vapor from the Amazon region into central and southern South America mainly during summer (e.g., Berri and Inzunza, 1993;Nogués-Paegle and Mo, 1997;Saulo and Nicolin, 2000;Silva Dias, 2000;Marengo et al, 2004), generating turbulence through shear and participating actively as trigging mechanism for the formation of severe storm over the Southeast/South of Brazil and Northern Argentina (e.g., Velasco and Fritsch, 1987;Guedes and Silva Dias, 1985;Salio et al, 2002;Nicolini et al, 2002;Nieto Ferreira et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Inter-El Niño variability and its impact on the South American low-level jet east of the Andes during austral summer − two case studies

Silva¹,

Ambrizzi²

2006

Adv. Geosci.

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“…While the La Plata Basin, in SESA, is particularly dominated by large and intense MCSs, the rainfall in the Amazon Basin comes partly from smaller MCSs and partly from frequent showers and thunderstorms. In this region, most convective systems are smaller (average area less than 1 x 1 0 5 km 2 ) and have shorter lifetime (3-6 hours) than MCCs (Carvalho and Jones 2001;Carvalho et al 2002a;Nieto Ferreira et al 2003).…”

Section: Mesoscale Featuresmentioning

confidence: 97%

Synoptic and Mesoscale Processes in the South American Monsoon

Grimm

Dias

2011

The Global Monsoon System

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The general features of the South American monsoon system (SAMS) are reviewed, but particular emphasis is put on its synoptic and mesoscale processes. During austral summer, the daily precipitation variability over tropical South America results mainly from the combined action of equatorial trades, easterly tropical disturbances, and the equatorward incursions of midlatitude synoptic wave systems. In the subtropics and western Amazon basin it is largely explained by frequent northward incursions of mid-latitude systems, affected by the Andes topography. There are different types of influence from frontal systems, which lead to different spatial organization of tropical convection, and different development of mesoscale convective systems (MCSs). MCSs are strongly modulated by the diurnal cycle and by transient synoptic systems, as well as influenced by mesoscale effects such as jets and other topographically forced circulations and surface atmosphere interactions. There are also mesoscale features associated with aerosols and land cover (deforestation). The jet with most extensive influence in the SAMS is the South American low-level jet east of the Andes. There are major regional differences in the structure, intensity, and diurnal cycle of rainfall systems. While the La Plata Basin (LPB) is particularly dominated by large and intense MCSs, the rainfall in the Amazon Basin comes partly from smaller MCSs and partly from frequent showers and thunderstorms. The diurnal cycle of convective cloudiness during the summer rainy season is generally tied to the diurnal march of the insolation, but is also influenced by regional factors. The peak is at afternoon/early evening in most of the monsoon region, while a nocturnal precipitation maximum is observed in the subtropical plains (LPB). Monsoon precipitation and its extreme events are modulated by several intraseasonal oscillations, including the Madden-Julian oscillation. The maximum intraseasonal variability is concentrated in Central-East Brazil, including the South Atlantic Convergence Zone. The frequency and intensity of extreme precipitation events is also modulated by other climatic oscillations, such as the El Nifio-Southern Oscillation.

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Variability of South American Convective Cloud Systems and Tropospheric Circulation during January–March 1998 and 1999

Cited by 57 publications

References 35 publications

Relationships between Upper-Level Circulation over South America and Rainfall over Southeastern South America: A Physical Base for Seasonal Predictions

Relationships between Upper-Level Circulation over South America and Rainfall over Southeastern South America: A Physical Base for Seasonal Predictions

Inter-El Niño variability and its impact on the South American low-level jet east of the Andes during austral summer − two case studies

Synoptic and Mesoscale Processes in the South American Monsoon

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