Statistical Analysis of Madden-Julian Events Using Time Series Indices.

The Madden-Julian Oscillation (MJO) is the dominant mode in the tropical atmosphere on sub-seasonal time scales, with a strong influence on the tropical weather and impacts on higher latitudes. Although it is an in depth-studied phenomenon, its intensification and attenuation mechanisms are not fully understood. The purpose of this communication is to analyse the statistics of MJO events using the Wheeler and Hendon index.
In our framework an MJO event takes place when the amplitude of the index is above a threshold for a certain number of days, depending on the averaging of the signal. With this, we define the maximum amplitude of an event, its duration and its size which is the sum of the amplitudes along the duration of an event.
We then analyse how the statistical properties change under variations in the definition of events. We further explore whether the tails of the event distributions are heavy tailed. As MJO interacts with other phenomena and has impacts on higher latitudes we compare the statistics of the MJO with other atmospheric indices. These statistical analyses may contribute to the knowledge of the intensification and attenuation processes that constitute the basic dynamics of the MJO.