Dual-Satellite Retrievals of Tropical Ice Cloud Particle Shapes and IWC During CRYSTAL-FACE: Comparisons With In-situ and Ground Site Observations

The study consists of (i) evaluating a satellite shape retrieval by comparing its results with in-situ observations within tropical ice clouds (ii) evaluating the impact of the shape retrieval on the satellite IWC estimation and (iii) comparing the satellite IWC with ground-based radar values. The particle shape retrieval uses dual-satellite observations at 650 nm. This method takes advantage of the sensitivity of bi-directional observations in the visible domain to the ice crystal phase function. The phase function is itself mainly a signature of the particle shape in the visible domain, as most of the ice crystals have sizes larger than the wavelength. The method used for retrieving the particle shape has been applied to several cases of observations in the past (Chepfer at al. 2002), but its performance has never been evaluated against in situ observations for tropical ice clouds. The paper will primarily present the comparisons between the shapes as retrieved from satellite and in-situ data. Moreover, the current satellite retrieval of IWC are using particle size retrieval as deduced from infrared wavelengths. Those particle size retrievals require the use of an a-priori assumption of the particle shape that significantly impacts the results. The second part of this study will focus on the potential improvement of the satellite IWC estimation using the ice crystal shape as constrained by the dual-satellite method. Finally, the resulting cloud IWC will be compared to the ones obtained from radar ground based sites.