Observed Precipitation variability induced by ENSO

SANTIAGO HURTADO; EDUARDO AGOSTA SCAREL

Guayaquil

Conferencia; IV International Conference on El Niño Southern Oscillation: ENSO in a warmer Climate; 2018

CIIFEN y CLIVAR

The Argentinian Chaco region (ACR) is highly sensitive to precipitation variability because of water scarcity during dry season. The work aims at clarifying the hemispherical/global climate forcing that drives precipitation in the region at inter-annual scale. The precipitation data was acquired from the network provided by the Chaco Province Water Authority, consisting in 64 gauge stations over the ACR in the period 1954-2010. The annual precipitation cycle was statistically divided into two seasons: a wet season (from October to April) and a dry season (from May to September). A spatial cluster analysis was performed by means of Principal Component Analysis technique, yielding four subregions in ACR. For every subregion a representative precipitation index for each season (dry and wet) was calculated and further examined. First, trends were estimated and removed if significant. Secondly, a spectral analysis was computed, reveling periodicities that could be related to the low and high frequency variability of the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole. The Yamamoto test for climatological jumps was calculated for each precipitation index and the running correlation between the precipitation index and climatological indices were compute to determine different periods of potential changes in  teleconnections. For those specific periods, composite anomalies of atmospheric and oceanic variables were computed for high index values and low index values. The composites revealed that high and low values of precipitation are directly associated with ENSO, showing high inter-El Niño variability. Particularly, most of dry years in western ACR are linked to La Niña events. The El Niño signal is less noticeable in eastern ACR.