Sulphur dioxide plume structure by mask correlation spectroscopy

A method for describing two dimensional plume structure using a ground based remote sensing technique, mask correlation spectroscopy, is presented. It consists essentially of a series of optical depth measurements at different zenith and azimuth angles. By geometrical projection and interpolation one can obtain the "isopleths", which represent the contours of gas density inside the plume. This method has been tested in the field and some typical results for different meteorological conditions are given. The limitations of the method and possible future developments are discussed.