Qualitative classification of the La Niña events

Abstract

La Nina is a cold episode of the El Nino Southern Oscillation (ENSO) phenomenon which is the strongest climatic signal on the inter-annual time scale; besides it greatly affects the world population. It plays an important role in formation of climate and environment anomalies. Based on the global HadISST datasets on sea surface temperature in the Nino3.4 region of the equatorial Pacific in 1870 – 2013 and the South Oscillation index (SOI) data, the La Nina events are selected and described. The obtained results are used as a ground for classifying the La Nina events. Taking into account typical variability of three main characteristics, i.e. intensity, duration and maximum SOI level, three types of the La Nina events are selected using the objective cluster analysis method. Three types of the La Niña events are distinguished by the objective classification. Type I is characterized by maximum duration (more than two years) and the highest intensity, type II – less pronounced features: moderately weak intensity and mid duration, and type III – low intensive and low- or mid-enduring La Nina events with low values of the Southern Oscillation index. Quasi-periodicity, apparently, conditioned by low-frequency variability in the ocean-atmosphere system is characteristic of the anomalies’ temporal variation corresponding to each of the distinguished types.

Keywords

La Niña, El Niño – South Oscillation (ENSO), South Oscillation index, Pacific Ocean region.

DOI: 10.22449/1573-160X-2015-3-14-24

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