Teleconnections between the Peruvian Central Andes and Northeast Brazil during Extreme Rainfall Events in Austral Summer

Abstract

Extreme precipitation events in the Peruvian Andes have significant socioeconomic impacts, yet their atmospheric dynamics are poorly understood. Here austral summer (December–March) wet and dry spells and their continental- and large-scale teleconnections are analyzed using reanalysis, gridded, and in situ precipitation data. Dry and wet spells in the Peruvian Andes show a pervasive dipole pattern with precipitation anomalies of the opposite sign over northeastern Brazil. Composite anomalies of various atmospheric fields during extreme precipitation events indicate that this dipole is related to large-scale adjustments in the upper-tropospheric Bolivian high–Nordeste low system, which in turn are modulated by northward-propagating extratropical Rossby wave trains. At upper- and midtropospheric levels, westerly wind anomalies over the Peruvian Andes suppress moisture flux from the Amazon during dry events, while wet events are characterized by opposite conditions. Yet, while easterly wind anomalies appear to be a prerequisite for heavy precipitation events in the region, they are not a sufficient forcing, as dry days can still occur during such periods. Dry spells in the Peruvian Andes appear to be linked to weakened convective activity over the western tropical Pacific, consistent with the previously documented El Niño influence over the region. Extreme dry and wet spells in northeastern Brazil only show a weak link to precipitation anomalies of the opposite sign over Peru but are strongly coupled with changes in the position and strength of the Nordeste low and the South Atlantic convergence zone.

Comparing peasants' perceptions of precipitation change with precipitation records in the tropical Callejón de Huaylas, Peru

“…We developed the criterion to meet the agricultural view of the peasants' report analyses. Thresholds are, as a consequence, different from those one would obtain when following climatological/statistical criteria such as in Marengo et al (2001), Nieto-Ferreira and Rickenbach (2011) or Sulca et al (2016). It is also worth mentioning explicitly that each wet spell stands for 1 week of relatively dry conditions (whereas the date used in Fig.…”

The Forest Effects on the Isotopic Composition of Rainfall in the Northwestern Amazon Basin

“…Some authors sustain the notion that during the Last Glacial Maximum a strong east‐west rainfall isotope gradient along the Amazon basin may have resulted from reduced water recycling, as consequence of a widely drier Amazonia, leading to reduced plant transpiration (Wang et al, ). On the other hand, other authors claim that the spatial variability in the isotope rainfall composition resulted from an east‐west precipitation dipole (Sylvestre et al, ; Cruz et al, ; Cheng et al, ) associated with an upper‐level atmospheric wave response to enhanced monsoon circulation, known as the Bolivian High‐Nordeste Low system (Chen et al, ; Lenters & Cook, , ; Sulca et al, ). In this scenario, the increased convective activity and precipitation over the tropical Andes and western Amazon is balanced by enhanced subsidence over Northeastern Brazil, leading to an antiphased precipitation pattern between the western and eastern Amazon, rather than pervasive dry conditions.…”

Impacts of different ENSO flavors and tropical Pacific convection variability (ITCZ, SPCZ) on austral summer rainfall in South America, with a focus on Peru

“…On the other hand, below average precipitation prevails in the tropical Andes during El Niño (e.g. Aceituno, 1988;Instituto Geofísico del Perú, 2005a), primarily due to upper-levels westerly wind anomalies (Vuille, 1999;Garreaud et al, 2009;Sulca et al, 2016). The same westerly wind anomalies and the associated precipitation deficit at same time also lead to negative glacier balance mass along the tropical Andes during El Niño (Francou et al, 2004;Vuille et al, 2008).…”

“…During the austral summer, Atlantic SST variability does not have an important influence on rainfall over the Altiplano region (Vuille et al, 2000a;Münnich and Neelin, 2005), the Peruvian central Andes (Instituto Geofísico del Perú, 2005b;Silva et al, 2008) or the Ecuadorian Andes (Vuille et al, 2000b). Indeed, teleconnections between SST in the tropical Pacific Ocean appear dominant in modulating rainfall variability in the Andean region, considering several timescales, from intra-seasonal to decadal (Garreaud, 1999;Segura et al, 2016;Sulca et al, 2016).…”

“…Garreaud and Aceituno, 2001;Vuille and Keimig, 2004). Even, on sub-seasonal timescales, Sulca et al (2016) pointed out that dry spells in the Peruvian central Andes are associated with the northward displacement of the SPCZ during the austral summer. Moreover, Vera et al (2004) showed that differences in ENSO impacts in South America in boreal spring are associated with the behaviour of the SPCZ and the propagation of stationary Rossby waves in the south Pacific and into South America.…”