Articles | Volume 42
Adv. Geosci., 42, 73–81, 2016
https://doi.org/10.5194/adgeo-42-73-2016
Adv. Geosci., 42, 73–81, 2016
https://doi.org/10.5194/adgeo-42-73-2016

  26 Aug 2016

26 Aug 2016

Tropical and Extratropical predictions of the summer and autumn Niño3.4 Index: a comparison

Miguel Tasambay-Salazar1,2, María José OrtizBeviá1, Antonio RuizdeElvira1, and Francisco José Alvarez-García1 Miguel Tasambay-Salazar et al.
  • 1Departamento de Física y Matemática, Universidad de Alcalá, Alcalá de Henares, 28801, Spain
  • 2Facultad de Informática y Electrónica, Escuela Superior Politécnica de Chimborazo, Riobamba, EC060155, Ecuador

Abstract. The El Niño-Southern Oscillation (ENSO) phenomenon is the main source of the predictability skill in many regions of the world for seasonal and interannual timescales. Longer lead predictability experiments of Niño3.4 Index using simple statistical linear models have shown an important skill loss at longer lead times when the targeted season is summer or autumn. We develop different versions of the model substituting some its variables with others that contain tropical or extratropical information, produce a number of hindcasts with these models using two different predictions schemes and cross validate them. We have identified different sets of tropical or extratropical predictors, which can provide useful values of potential skill. We try to find out the sources of the predictability by comparing the sea surface temperature (SST) and heat content (HC) anomalous fields produced by the successful predictors for the 1980–2012 period. We observe that where tropical predictors are used the prediction reproduces only the equatorial characteristics of the warming (cooling). However, where extratropical predictors are included, the predictions are able to simulate the absorbed warming in the South Pacific Convergence Zone (SPCZ).

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Short summary
We investigate the factors that determine the longer lead ENSO predictability in the 1980-2012 period. We compare different versions of the prediction model using some variables that contain tropical or extratropical information.We observe that where tropical predictors are used the prediction reproduces only the equatorial characteristics of the warming (cooling). However, where extratropical predictors are included, the predictions are able to simulate the absorbed warming in the SPCZ.