Potential retrieval of dominating crystal habit and size using radiance data from a dual-view and multiwavelength instrument: A tropical cirrus anvil case

The potential to retrieve dominating crystal habit, size and bulk optical depth for tropical anvil cirrus using radiance measurements from a dual-view and multiwavelength instrument is demonstrated. The radiance measurements are taken from the along-track scanning radiometer (ATSR-2) instrument at wavelengths of 0.87 and 1.6 mu m The ATSR-2 has a dual-view capability being able to make radiance measurements at near nadir and at a forward view of 55 degrees of the same cloud. The dual-view radiance measurements at 0.87 mu m are best fitted by a polycrystal phase function and estimates of crystal size (crystal size in this paper is defined in terms of the crystal maximum dimension) using the 1.6 mu m channel vary between 25 and 100 mu m. Two other tropical cirrus anvil cases are used to show qualitatively the variation of crystal size with anvil maturity. Quantitative comparisons are made with observations taken from the Central Equatorial Pacific Experiment with regard to dominating habit and cloud-top crystal size.