Retrieval of Low-Level Marine Cloud Parameters from Airborne Observation Data

摘要

研究概要:It is of great interest to investigate the radiative properties on the cloud optical, microphysical, and geometrical parameters, in particular, of low-level marine clouds which play crucial influence on a global climate system. Top height, base height, and geometrical thickness of cloud layer are considered here as cloud geometrical parameters. These parameters are very important because top and base heights are the factors which govern the strength of greenhouse effect through the thermal radiation from/to cloud layer, whereas the geometrical thickness is the key parameter for the estimation of gaseous absorption in cloud layer where multiple scattering process dominates. Some studies have shown that information of a few spectral regions including oxygen A band, enabled us possible to retrieve the cloud geometrical parameters as well as the optical thickness, the effective particle radius of cloud. In this study, an algorithm has developed to retrieve simultaneously the cloud optical thickness, effective particle radius, top height, and geometrical thickness of cloud layer from the spectral information of visible, near infrared, thermal infrared, and oxygen A band channels. This algorithm was applied to the actual airborne data which included the above four channels and targeted at the low-level marine clouds off the coast of California in summer. The retrieved results seems to be almost consistent to the in situ microphysical observation although further validation studies are required for the cloud geometrical parameters in particular.