Abstract

GALVAN, Romina; CARBONETTI, Micaela; GENDE, Mauricio  and  BRUNINI, Claudio. Impact of the extreme 2015-2016 Enos event on the geometry of the earth surface in the equatorial region of South America. Geoacta [online]. 2017, vol.42, n.2, pp.23-44. ISSN 1852-7744.

El Niño-Southern Oscillation (ENSO) is an atmospheric-oceanic phenomenon that originates in the equatorial Pacific Ocean. It is characterized by two phases: the warm or “El Niño” phase, and the cold or “La Niña” phase. They respectively refer to a significant increase or decrease of the surface temperature of the Pacific Ocean with respect to normal values.One of the main consequences of this abnormality is an alteration of the hydrological cycle in the rainfall patterns in South American and Caribbean region. Such disturbance can cause non-periodic variations in both the rainfall patterns and water body storages located on the surface or near it. The immediate consequence is the pressure that such bodies exert on the earth's crust change. They can cause geometric movements of the earth's crust and gravity measurement changes.This paper is focused on the geometric effects of this phenomenon on the GNSS station positions of SIRGAS-CON network. Time periods for whichEl Niño or La Niña occurred are recognized using the Oceanic Niño Index (ONI). The impact of the most significant events, occurred between 2008-2012 and 2015-2016, over rainfall patterns and on total water storage is analyzed. Regions of characteristic behaviour of each phase are recognized using global precipitation model CMAP. The greatest differences with respect to average values occur between December 2015 and March 2016. A decrease up to 60% in rainfall is observed in the northern region of the South American continent. In order to evaluate water storage anomalies GRACE satellite mission data is assessed. A decrease up to 60 cm in Brazil northern region and an increase up to 40 cm in the southern region is observed during 2015-2016 El Niño event. Furthermore, the effect on the vertical component of the coordinates is investigated. Positive anomalies are found in the northern region of South America during the 2015-2016 event, while a significant opposite effect is detected in the southern equatorial region.

Keywords : Geodesy; GNSS; El Niño-Southern Oscillation; South America.

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