Influence of local dust source and stochastic fluctuations on Saharan aerosol index dynamics

We analyse time series of the Aerosol Index, a parameter related to the aerosol con- tent and retrieved by satellite observations. In particular, we consider data recorded on oriental part of Sahara. A stochastic equation describes the behaviour of the Aerosol Index as occurs in Italy, but out of a stochastic resonance regime. We prove that, in the oriental part of Sahara, local dust source is simply linear superimposed to noise so that a stochastic resonance regime is not set. Furthermore, we nd that the local dust emission strongly in uences the Aerosol Index data and it is responsible for about 78% of the annual periodicity in the signal.