Study of the diffraction pattern of cloud particles and the respective responses of optical array probes
Abstract. Optical array probes (OAPs) are classical instrumental
means to derive shape, size, and number concentration of cloud and
precipitation particles from 2-D images. However, recorded 2-D images are
subject to distortion based on the diffraction of light when particles are
imaged out of the object plane of the optical device. This phenomenon highly
affects retrievals of microphysical properties of cloud particles. Previous
studies of this effect mainly focused on spherical droplets. In this study we
propose a theoretical method to compute diffraction patterns of all kinds of
cloud particle shapes in order to simulate the response recorded by an OAP.
To check the validity of this method, a series of experimental measurements
have been performed with a 2D-S probe mounted on a test bench. Measurements
are performed using spinning glass discs with imprinted non-circular opaque
particle shapes.