Stochastic Study of Detection of Aerosol Increase Due to Asian Dust and Outdoor Facility Construction

概要

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The real-time detection of an increase in the atmospheric aerosol number concentration due to Asian dust and outdoor facility construction was studied with a stochastic method, called FUMI theory (function of mutual information). It is difficult to find this event in its early stage by means of instrumental analysis, since the instrumental output originating from the event is so small that it can almost be hidden under, or rather overlapped with, the omnipresent instrumental noise. Difficulty comes from the fact that the background and objective signal are both subject to random fluctuations. If an observed value exceeds a detection limit, the hypothesis that the observed one originates from a natural cause other than the Asian dust or outdoor facility construction would be denied. The following methods are elaborated to make the early detection of the event more practical with satisfactory precision: continuous shift of a time domain used for the detection-limit estimation; removal of spike noise and output judged as a signal in our method from the domain; classification of a signal in the scale of the detection limit.