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 content 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 find that the local dust emission strongly influences the Aerosol Index data and it is responsible for about 78% of the annual periodicity in the signal.