A comparison of the structure and dynamics of Global atmospheric oscillation in reality and in the CMIP5 climate models

Abstract

In this paper, global fields of mean anomalies of the sea-level atmospheric pressure and the surface air temperature are constructed for positive and negative phases of a recently discovered by Russian scientists Global atmospheric oscillation (GAO) with El Niño and La Niña as its elements. This is done using observations and their re-analyses, as well as the results of experiments with climate models. A GAO index is proposed, and its spectra, as well as spectra of El Niño – Southern Oscillation (ENSO), are calculated. It is shown that some of the modern models of ocean-atmosphere general circulation of the international Coupled Model Intercomparison Project Phase 5 (CMIP5) reproduce well the GAO spatial structure. The model temporal energy spectra, however, differ from the real ones in the general variation of the energy spectra of interannual-decadal oscillations, as well as in the periods of specific peaks in this range. A comparison of CMIP5 experiments called Historical and piControl shows that the climate models with the 11-year solar activity cycle forcing reproduce the GAO periodicity more accurately. It is concluded that the differences between the model spectra and the real ones cause major errors in the predictions of the El Niño onset for more than half a year.