It is of great interest to investigate the properties on the cloud optical, microphysical, and geometrical parameters, in particular, of low-level marine clouds which have crucial influence on the global climate system. Top height, bottom height, and geometrical thickness of cloud layer are considered here as cloud geometrical parameters. These parameters are very important, because top and bottom 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 a cloud layer where multiple scattering process dominates.

In this study, an algorithm was developed to retrieve simultaneously 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 First ISCCP Regional Experiment (FIRE, conducted in 1987) airborne data which included the relevant four channels and targeted at the low-level marine clouds off the coast of California in summer. The retrieved results seems to be comparable to the in situ microphysical observation. But, for the cloud geometrical parameters (top and bottom heights), compared to lidar observation, variance of the retrieved cloud bottom height is rather large for multilayered cloud system in particular.

The other data sets, recently observed in airborne and spaceborne measurement, will further be analyzed, so as to confirm the algorithm's utility and check the limitation on a regional and global scale, respectively. The algorithm will be applied to the Global Imager (GLI) spaceborne data set to make global cloud products. The GLI will be onboard with Advanced Earth Observing Satellite-II (ADEOS-II) satellite which will be launched in 2002 by National Space Development Agency of Japan (NASDA).