The Orinoco low‐level jet during El Niño–Southern Oscillation

Abstract

This study shows the influence of El Niño-Southern Oscillation (ENSO) over the seasonal and diurnal variability of the Orinoco low-level jet (OLLJ) during the December-January-February (DJF) season. Results show changes in the occurrence and intensity of the OLLJ winds during the phases of ENSO (El Niño and La Niña) in relation to Neutral conditions. During El Niño (La Niña), the OLLJ days decrease (increase) over the mid and exit of the OLLJ corridor. Furthermore, the mean wind vertical profiles (and the intensity of the diurnal cycle) decrease (increase) with values ranging from 5 to 9 mÁs −1 . We highlight that the OLLJ days decrease (increase) in January (February) during El Niño (La Niña) up to 24% (15%). These changes are modulated by the pressure gradient between the Atlantic subtropical high and the nearequatorial trough regions that decreases (increases) during El Niño (La Niña) and thus induces a decrease (increase) of the OLLJ winds. Moreover, the water vapour flux and precipitation reduce during both phases of ENSO along the OLLJ corridor. This work shows new insights on the OLLJ features during ENSO, which contributes to improving our understanding of the processes that influence the hydro-climatology of northern South America.

Precipitation over northern South America and the far‐eastern Pacific during ENSO: Phase synchronization at inter‐annual time scales

“…The ChocoJet winds show PS with precipitation over western Colombia for both states of ENSO, which can be associated with the increase (decrease) in ChocoJet winds during LN (EN) and the increase (decrease) in precipitation over western Colombia (Poveda & Mesa, 2000). Finally, some PS spatial patterns for precipitation and low‐level winds at 925 hPa are coincident over the LLJ regions, these results suggest phase synchrony between low‐level winds and precipitation, relationship that have been mentioned using other approaches for each LLJ case by Wang (2007); Poveda and Mesa (2000); Builes‐Jaramillo et al (2022a, 2022b).…”

“…For example, (i) the Caribbean LLJ (CLLJ) has a different relationship with ENSO during its active seasons (JJA and DJF). During DJF, a weak (strong) easterly CLLJ corresponds to warm (cold) SST anomalies in the tropical eastern and central Pacific, whereas in JJA, a strong (weak) easterly CLLJ is associated with warm (cold) SST anomalies in the tropical Pacific (Wang, 2007); (ii) The ChocoJet, which is active during SON, is associated with an reduction (increase) in precipitation over western Colombia during EN (LN) (Poveda & Mesa, 2000; Yepes et al, 2019) and (iii) The Orinoco LLJ (OLLJ), which is active during DJF and during EN (LN), the mean wind vertical profiles (and the intensity of the diurnal cycle) decreased (increased) up to 24% (15%) (Builes‐Jaramillo et al, 2022a, 2022b). Although there have been advances in our understanding of the relationships between ENSO and precipitation in the NSA and FEP, questions remain and we are still far from a robust understanding of the impacts, inter‐basin climate interactions and possible consequences in the context of climate change (Cai et al, 2020).…”

Moisture Recycling in the Colombian Andes

“…(2014) showed that the Tropical North Atlantic and the far eastern tropical Pacific are connected through aerial rivers that flow over the Amazon River basin and the Andes, particularly from April to October. Also, the Tropical North Atlantic feeds the easterly trade winds and the Orinoco LLJ which in turn hits the foothills of the Eastern Andes providing the input moisture and energy for diverse land‐atmosphere interactions as initiating convective processes (Builes‐Jaramillo et al., 2022; Espinoza et al., 2020; Jimenez‐Sánchez et al., 2019; Poveda et al., 2020). As reported in previous studies, northwestern Amazon modulates moisture sources for continental precipitation (Dominguez et al., 2022; Gimeno et al., 2012; Poveda et al., 2014; Staal et al., 2018; Weng et al., 2018; Zemp et al., 2014).…”

“…The CA block westerly and easterly winds that are primary sources for the high rainfall rates witnessed in the Pacific and Orinoco boundaries. These regions are sensitive to ENSO‐related variability (Figures 7 and 8) and are part of the complex mechanism of interaction between low‐level jets such as the Chocó (Poveda et al., 2014, 2020), Caribbean (Amador, 2008; Durán‐Quesada et al., 2012; Poveda & Mesa, 1999), and Orinoco (Builes‐Jaramillo et al., 2022; Jiménez‐Sanchez et al., 2019; Martínez et al., 2022). Finally, the assumption of well‐mixing of advective and evaporative sources of atmospheric vapor needs to be better evaluated in the context of the Colombian Andes for WAM‐2.…”

“…Their complex geomorphology comprises three branches (Western, Central, and Eastern) separated by two major long intra‐Andean valleys drained by the Magdalena and Cauca rivers (Figure 2a). Research directly or indirectly related to the hydroclimate of this region includes studies of variability at diurnal time‐scales (Bedoya‐Soto, Aristizábal, et al., 2019; Poveda et al., 2005), annual time and seasonal time‐scales (Alvarez‐Villa et al., 2011; Poveda, 2004; Urrea et al., 2019; Vallejo‐Bernal et al., 2021); interannual time‐scales (Bedoya‐Soto, Poveda, et al., 2019; Córdoba‐Machado et al., 2015a, 2015b; Posada‐Marín et al., 2018; Poveda and Mesa, 1997, 2000; Poveda et al., 2001, 2006, 2011, 2020); activity of low level‐jets and moisture sources (Arias et al., 2015; Builes‐Jaramillo et al., 2022; Durán‐Quesada et al., 2012; Hoyos et al., 2018, 2019; Jiménez‐Sánchez et al., 2019; Morales et al., 2021; Poveda et al., 2014; Poveda & Mesa, 2000; Yepes et al., 2019); activity of mesoscale convective systems (Jaramillo et al., 2017; Poveda et al., 2020; Sakamoto et al., 2011; Zuluaga & Houze, 2015); and climate change (Carmona & Poveda, 2014; Mesa et al., 2021; Pabón‐Caicedo et al., 2020; Sierra et al., 2015, 2021); among others.…”