ENSO-related rainfall anomalies in South America and associated circulation features during warm and cold Pacific decadal oscillation regimes

Abstract

El Niño/Southern Oscillation (ENSO)-related patterns of monthly reanalyzed upper-level circulation data and monthly rainfall time series over South America are revised for the 1948-1999 period considering the phases of the Pacific interDecadal Oscillation (PDO). The El Niño (EN) related composites show differences relative to the PDO phases as well as seasonal differences. EN signals in the South American rainfall are more conspicuous for the warm PDO (WPDO) regime, when seasonal differences are more pronounced, than for the cold PDO (CPDO). Differences for the 200-hPa stream function composites seem to determine the precipitation composite differences. In fact, the negative precipitation anomalies over northeast Brazil and the excessive rainfall to the south are explained respectively by a cyclonic center over eastern and northeastern Brazil and a weak anticyclonic center over southeastern South America for the WPDO regime. Positive precipitation anomalies over southeastern South America are located in a southern position for the CPDO regime when compared to those for the WPDO regime. These anomalies might be related to a strengthened upper-level subtropical jet stream associated with strong cyclonic circulation extending over southern South America for the CPDO regime. With regard to the linear and nonlinear parts of the precipitation anomaly patterns related to the ENSO, the nonlinear component is considerably smaller than the linear component, in particular, over northern and southeastern South America. This suggests that the linear approach of the South American precipitation response to the ENSO seems to be appropriated.

Interannual relations between South American rainfall and tropical sea surface temperature anomalies before and after 1976

“…These results are in agreement with previous composites of the summer precipitation anomalies for the ENSO extremes considering the PDO phases (Andreoli and Kayano, 2005;Kayano and Andreoli, 2007). Andreoli and Kayano (2005) explained most of the differences in the ENSO-related rainfall composites by the differences in the 200-hPa stream function composites between the PDO phases. Thus, the differences between the two periods reflect, in part, ENSO teleconnections over South America with the PDO background acting to enhance (weaken) the correlations when ENSO and PDO are in the same (opposite) phase.…”

“…Andreoli and Kayano (2005) discussed the relationships of ENSOrelated rainfall and circulation anomalies over South America and the PDO. They found that El Niño signals in South American rainfall are more conspicuous for the warm PDO regime than for the cold PDO regime.…”

Análises estatísticas das tendências de elevação nas séries anuais de temperatura mínima do ar no Estado de São Paulo

“…A comparação entre as duas regiões, geograficamente bastante próximas, não revelou concomitância nas tendências contínuas de elevação da Tmín. Em outro aspecto, o intervalo temporal de aproximadamente 12 anos entre a data de mudança de local do posto e a intersecção entre u(tn) e u*(tn), aliada às afirmações de MELLO et al (1994) relativas à série As influências dessa oscilação de escala multidecadal na variabilidade climática da América do Sul foram investigadas por ANDREOLI e KAYANO (2005) e KAYANO e ANDREOLI (2007). Nesses trabalhos, verifica-se que para a precipitação pluvial esse fenômeno age de maneira construtiva (destrutiva) quando o El Niño/Oscilação Sul (ENOS) e a ODP estão na mesma (oposta) fase.…”

Possible influences of pacific decadal oscillation in the ten day based radio between actual and potential evapotranspiration in the region of Campinas, São Paulo State, Brazil

“…As for the South American climate variability, only more recently has it been interpreted in the context of the PDO effects (ANDREOLI and KAYANO, 2005;KAYANO and ANDREOLI, 2007). These papers showed that the PDO creates a background for the ENSO teleconnections for the South American precipitation, acting constructively (destructively) when the ENSO and the PDO are in the same (opposite) phase.…”