Light Backscattering by Ice Crystals of Cirrus Clouds Within the Physical Optics Approximation Alexander Konoshonkin, Anatoli Borovoi, Natalia Kustova, Zhenzhu Wang, Dong Liu and Chenbo Xie EPJ Web Conf., 237 (2020) 08011 Published online: 07 July 2020 DOI: 10.1051/epjconf/202023708011