Cloud Research for Yielding Sophisticated Treatment of Atmospheric Light-scattering

Objective

In recent decades the significance of high-level cirrus clouds in shaping our climate has gained recognition. These clouds play a pivotal role in Earth's radiation balance - both by scattering incoming solar radiation and absorbing outgoing thermal radiation. Due to their high altitude cirrus clouds are completely composed of tiny ice crystals. To correctly quantify the role of cirrus clouds in climate, it is crucial to determine the optical properties of cirrus ice crystals reliably. Since there is no analytical solution available for solving the light scattering by nonspherical ice crystals, extensive efforts have been made to develop numerical models. Recently I demonstrated that nano-scale structures on ice crystals (such as surface roughness) are decisive in determining their optical properties in the solar spectrum. Unfortunately, these structures are not well represented in numerical models, leading to significant discrepancies between modelled and observed ice optical properties. This project aims at developing a much needed realistic optical model for roughened ice crystal. For the first time I will apply the treatment of rough surfaces in technical optics for the optical treatment of atmospheric ice crystal surfaces. Combining novel nano-printing of realistic ice surfaces with airborne observations, a physically-based model will be developed to accurately account for the optical effects of ice crystal surface structures at solar wavelengths. Understanding the optical effects of ice crystal surface roughness marks a breakthrough in atmospheric science, providing the foundation for the creation of a comprehensive dataset of ice optical properties for remote sensing retrievals, a crucial achievement for the success of upcoming satellite missions like Metop - Second Generation, where precise ice optical properties are essential for high-quality meteorological observations.