ABSTRACT
This chapter describes the techniques and recent results pertaining to the measurement of elastic scattering and absorption of aerosols. The information on aerosol properties that can be retrieved from measurements of spectral and angular dependence is not dissimilar. Most notably, both the wavelength dependence of scattering and extinction and the angle dependence of scattering are functions of the size parameter, the ratio of the particle circumference to the wavelength of the light. Therefore, spectroscopy and angular measurement of intensity are closely related, and both can be used to retrieve the size, or size distribution, of aerosol particles. However, we observe that additional properties can be obtained from the angular dependence of scattering, by virtue of stronger sensitivity of scattering to particle shape, symmetry, and orientation and, for two-dimensional (2D) scattering patterns, the greater information content of the data. Moreover, for single particles, scattering is much easier to measure than extinction. In contrast, the opposite can be said to be true of measurements on multiple particles. Therefore, extinction and angular measurements are in some ways complementary to each other.
