Estimation of cloud physical parameters from airborne solar spectral reflectance measurements for stratocumulus clouds

Abstract

A new method is proposed to retrieve various cloud physical parameters of water clouds from the solar-flux reflectances at four wavelengths measured by using the airborne Multi-channel Cloud Pyranometer (MCP) system. The cloud optical thickness and the effective particle radius of the water-cloud layer can be simultaneously retrieved from the MCP reflectances. Under the assumption that cloud pressure height is known, the cloud liquid water content (LWC) can then be retrieved from the MCP reflectance. Finally, the in-cloud water vapor amount can be estimated from the MCP reflectance at the water vapor absorption-band channel. Using these directly retrieved parameters, we can estimate byproduct parameters such as integrated liquid water path, cloud particle concentration, and geometrical thickness of the homogeneous cloud layer. The present retrieval method was applied to the MCP spectral reflectance data obtained through aircraft observations for wintertime stratocumulus clouds over the ocean south of Tokyo, made as part of the Western North Pacific Cloud-Radiation Experiment. -from Authors