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Abstract

The interaction of solar radiation with ice particles in clouds plays a crucial role in redistributing solar light. Understanding this process is essential for accurate calculations of the shortwave radiative transfer in climate models and for retrieving cloud properties from satellite observations. However, current knowledge of the light scattering behavior of atmospheric ice particles is limited using simplified ice particle morphologies in optical models.To address this limitation, the Particle Habit Imaging and Polar Scattering (PHIPS) airborne probe was developed to obtain in-situ measurements of single atmospheric ice crystals. The PHIPS probe is a combination of a stereo microscopic bright field imager and a polar nephelometer that works on single particles. By using PHIPS, a unique and comprehensive dataset of microphysical properties and correlated angular light scattering functions of real atmospheric ice particles has been acquired from several aircraft campaigns.The acquired dataset is of high value for scientists developing and applying single particle light scattering models. By simulating the light scattering behavior of the observed crystals with the optical engineering software FRED, the study shows that even solid hexagonal crystals require surface roughness assumptions to accurately explain their light scattering function. The study tests two surface roughness models: the tilted-facet angle distribution method and the "smooth surface roughness" approach, which assumes scalar diffraction on wavelength-scale roughness features. The performance of these two models for the example crystals is discussed. Overall, this study demonstrates the importance of in-situ measurements for improving our understanding of the light scattering behavior of atmospheric ice particles.