Répartition spatiale de l'influence de l'ENSO sur les précipitations annuelles en Équateur

Rossel, Frédéric; Goulven, Patrick Le; Cadier, Éric

doi:10.7202/705348ar

Cited by 27 publications

(22 citation statements)

References 16 publications

(12 reference statements)

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“…For inter-Andean valleys as the Paute basin, ENSO influence is almost negligible due to their high elevation and eastward-oriented exposure towards the Amazon basin (Rossel et al, 1998;Célleri et al, 2007). Also, for the Amazon region, ENSO influence is negligible (Rossel et al, 1998), which confirms the findings of Bendix and Lauer (1992) that the Andes cordillera acts as weather divide. However, during 1982However, during -1983However, during and 1997However, during -1998, ENSO exceptional events affected Ecuador severely, thereby producing significant positive anomalies in precipitation countrywide.…”

Section: Study Areamentioning

confidence: 99%

Evaluation of downscaled estimates of monthly temperature and precipitation for a Southern Ecuador case study

Ochoa

Campozano

Sánchez

et al. 2015

Intl Journal of Climatology

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The downscaling of global climate models (GCMs) aims at incorporating finer scale information to their horizontal resolution in order to represent regional and local processes better. There are two main approaches to downscaling: statistical (based on data relationships between synoptic atmospheric variables and observations of local variables) and dynamical (based on the modelling of regional atmospheric processes and land–surface interactions). In this study, some predictive capabilities regarding the generation of station‐scale mean monthly temperature and rainfall of both a statistical artificial neural network (ANN‐based) and a dynamical weather research and forecasting (WRF‐based) downscaling approach are assessed. We have devised two versions of the statistical downscaling approach. One of them includes regional orographic variables as predictors to allow for spatial extrapolation; the other is purely local. Historical observational data, from the period 1990 to 1999, of two major watersheds in the Ecuadorian Southern Andes, the Jubones and Paute river basins, were used. Since, to a certain extent, the value added by downscaling techniques can be attributed to terrain information, it is worth noting that some characteristics of the selected catchments (as notorious altitude differences and the presence of qualitatively different precipitation regimes) provide a scientifically interesting location for exploring how finer scale effects are captured. For this reason, we concentrate on the ability of downscaling techniques to reproduce seasonality. A decade of evaluation proved that both approaches were able to qualitatively describe precipitation and temperature seasonal variations for different regimes at representative weather stations. Furthermore, the seasonality of precipitation represented by both downscaling approaches surpassed the seasonality representation of reanalysis data. However, shortcomings on the estimates were found. Specifically, dynamical downscaled precipitation estimates were prone to overestimation. Despite the fact that the considered downscaling approaches are different in nature, their ability to represent the high spatio‐temporal variability in this region highlights the importance of evaluating their strengths and limitations.

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Section: Study Areamentioning

confidence: 99%

Evaluation of downscaled estimates of monthly temperature and precipitation for a Southern Ecuador case study

Ochoa

Campozano

Sánchez

et al. 2015

Intl Journal of Climatology

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“…Hence, 3 monthly mean sea-surface temperature anomalies in the El Niño blocks 1 C 2 (0-10°S, 80-90°W) are used to identify El Niño and La Niña years (cf. Figure 7; Rossel et al, 1997). This method successfully identifies the well known El Niño events of 1982-83 and 1997-98, as well as less important events (e.g.…”

Section: Hydrological and Meteorological Datamentioning

confidence: 99%

Suspended sediment yield and metal contamination in a river catchment affected by El Niño events and gold mining activities: the Puyango river basin, southern Ecuador

Tarras-Wahlberg

Lane

2003

Hydrological Processes

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Abstract:The suspended sediment yield and the transfer of polluted sediment are investigated for the Puyango river basin in southern Ecuador. This river system receives metal (Cd, Cu, Hg, Pb and Zn) and cyanide pollution generated by mining, and is associated with large-scale hydrological variability, which is partly governed by El Niño events. Field sampling and statistical modelling methods are used to quantify the amount of mine tailings that is discharged into the basin. Annual suspended sediment yields are estimated using a novel combination of the suspended sediment rating method and Monte Carlo simulations, which allow for propagation of the uncertainties of the calculations that lead to final load estimates. Geochemical analysis of suspended and river bed sediment is used to assess the dispersion and long-term fate of contaminated sediment within the river catchment. Knowledge of the inter-and intra-annual variation in suspended sediment yield is shown to be crucial for judging the importance of mining discharges, and the extent to which the resultant pollution is diluted by river flows. In wet years, polluted sediments represent only a very small proportion of the yield estimates, but in dry years the proportion can be significant. Evidence shows that metal contaminated sediments are stored in the Puyango river bed during low flows. Large flood events flush this sediment periodically, both on an annual cycle associated with the rainy season, and also related to El Niño events. Therefore, environmental impacts of mining-related discharges are more likely to be severe during dry years compared with wet years, and in the dry season rather than the wet season. The hydrological consequences of El Niño events are shown to depend upon the extent to which these events penetrate inland. It is, thus, shown that the general conclusion that El Niño events can significantly affect suspended sediment yields needs evaluation with respect to the particular way in which those events affect a given catchment.

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“…Antizana 15 is located on the Amazonian slope of the Andes, 300 km east from the Pacific coast, which usually records strong local sea surface temperature anomalies (SSTA) during ENSO events (Niño 1 + 2 region). Several recent studies have discussed the significant changes in precipitation, cloud cover, and temperature that occur during ENSO all along the Pacific coast and the western slope of the Ecuadorian Andes [ Rossel et al , 1998; Bendix , 2000; Vuille et al , 2000b; Bendix et al , 2003]. The northeastern cordillera equally experiences significant temperature changes during ENSO periods, but precipitation anomalies during El Niño/La Niña years do not seem to be as pronounced as along the coast or in the northwestern Ecuadorian Andes [ Vuille et al , 2000b].…”

Section: Introductionmentioning

confidence: 99%

New evidence for an ENSO impact on low‐latitude glaciers: Antizana 15, Andes of Ecuador, 0°28′S

Francou¹

2004

J. Geophys. Res.

153

191

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[1] Continuous monthly mass balance measurements from the ablation zone of Antizana 15 glacier in the Andes of Ecuador between January 1995 and December 2002 indicate a strong dependence on El Niño-Southern Oscillation (ENSO). Over the 8-year period investigated, mass balance was negative all year round during El Niño periods but remained close to equilibrium (positive anomalies) during La Niña events. On seasonal timescales, mean ablation rates remain at a quite constant level all year round, but interannual variability shows much larger changes from year to year during the key periods February-May and September. This variability is caused by large differences that occur in the seasonal cycle during the two opposite phases of ENSO. Since ENSO is phase locked to the seasonal cycle with largest sea surface temperature anomalies around boreal winter, November-February, and the atmospheric response to ENSO is delayed by 3 months over the Ecuadorian Andes, year-to-year variations in mass balance are largest between February and May. Energy balance studies at the glacier surface indicate that high air temperature, which favors rain over snowfall, weak and sporadic snowfall, insufficient to maintain a high glacier albedo, low wind speeds, which limit the transfer of energy from melting to sublimation, and reduced cloud cover, which increases the incoming short-wave radiation, are the dominant factors related to El Niño, which tend to increase ablation. La Niña events on the other hand are characterized by colder temperatures, higher snowfall amounts, and to a lesser degree, more constant winds, factors which increase albedo and sublimation and therefore preclude melting at the glacier surface. The effects of ENSO variability are also important over the accumulation area, which represents up to 80% of the glacier surface during La Niña events (1999)(2000) and 45-60% in El Niño years. Since the accumulation rates increase during these cold periods, the specific net balance and the dynamics of the entire glacier are strongly affected. Longer mass balance records than this 8-year period are needed for conclusive answers about the dependence of the Ecuadorian glaciers on ENSO variability, but initial results suggest that the response observed on Antizana glaciers is very similar to what has been observed previously during ENSO periods on Andean glaciers in the outer tropics. The seasonal dependence on ENSO and the physical mechanisms linking ENSO with mass balance variations on Antizana, however, are different from the response observed on Andean glaciers in the outer tropics.

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Répartition spatiale de l'influence de l'ENSO sur les précipitations annuelles en Équateur

Cited by 27 publications

References 16 publications

Evaluation of downscaled estimates of monthly temperature and precipitation for a Southern Ecuador case study

Evaluation of downscaled estimates of monthly temperature and precipitation for a Southern Ecuador case study

Suspended sediment yield and metal contamination in a river catchment affected by El Niño events and gold mining activities: the Puyango river basin, southern Ecuador

New evidence for an ENSO impact on low‐latitude glaciers: Antizana 15, Andes of Ecuador, 0°28′S

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