A Simple Approximation for the Reflectance of a Thick Cloud in Gaseous Absorption Band and Its Application for the Cloud-Top Height Determination

This paper presents a new, simple, fast method to retrieve cloud altitude from measurements of light absorption in the strongest molecular band of oxygen (the A-band), centered at 761 nm, by the polarization and directionality of the earth's reflectance sensor. First, we assess the validity of the method against synthetic spectra as a function of realistic cloud scenarios and satellite observation geometries. The retrieval error estimate amounts, on average, to less than 500 m. Second, the hurricane Ileana, overpassed the August 30, 2012, off the coasts west of Mexico and Southern California, is selected as test bed for the comparison of our retrievals against independent and nearly coincident cloud data inferred with the Moderate Resolution Imaging Spectroradiometer onboard Aqua and the Global Ozone Monitoring Experiment 2 onboard MetOp-A. We find that our approach can accurately reproduce the cloud height patterns, as long as the clouds are not thin cirrus.