Abstract

This paper discusses an improved procedure for the inversion of aureole forward scattering measurements to obtain aerosol size distributions. It is shown that the use of finite differences of the high angular resolution forward scattering data significantly improves the inversion results compared with using the direct kernel and enables one to resolve the bimodal structure of typical volume size distribution. An addition of proper scaling of the absolute size distribution to the Twomey-Chahine inversion algorithm results in very fast convergence with only three iterations typically required. An averaging and smoothing procedure is used to remove the spurious features of the inverted size distribution. The inversion method has been tested using simulated angular scattering measurements for four different aerosol models. For measurements covering 1.08-10° at a wavelength of 0.25 μm, the size distributions were retrieved with a 15-30% rms error over the radii range between 0.2 and 6.0 μm, with a representative measurement noise of 4%. It is noted that the differential inversion technique is more sensitive to noise than the direct method, since differencing the measurements decreases the signal-to-noise ratio.

© 1985 Optical Society of America