The most important breath of life is the first breath.” |
Beside the Asian-Australian monsoon, rainfall over both Central America and tropical South America is the most important hydro-meteorological phenomenon in the tropics. Using a multiple spatiotemporal scale approach, the variability of South America rainfall was analyzed. Its interannual variability is affected by the El Niño Southern Oscillation (ENSO), which is noted by two out-of-phase patterns in the associated atmospheric teleconnection.
Although the role of the intraseasonal mode on tropical precipitation at the global scale is well known, documentation of this mode at continental scale on tropical South America, as a major pattern of variability of the summer rainfall regime, is not well understood. Here, we isolated two dominant modes in the interseasonal scale (12-24 and 30-60 day) and to relate extreme rainfall events to the variability and modulation of these perturbations. Thus, the 12-24 day mode, embedded and modulated by the 30-60 day mode, seems to be the dominant one. The intraseasonal (12-24 and 30-60 day) modes portray the quasi-periodic rainfall patterns over the tropics in South America. The synoptic systems embedded in these scenarios, mainly affected by both the warm and cold ENSO phases, are described. Synoptic (eastward) and diurnal high-frequency (westward) disturbances propagate and interact influenced by the cold and warm ENSO phases. During La Niña, positive anomalous precipitation is expected because of the constructive interference of these two modes, and during El Niño, the synoptic disturbance is suppressed. The figure is from Carrillo's MS thesis (2010) and represents this multi-scale interaction. |