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Communication Dans Un Congrès Année : 2019

Introducing the Version 4 CALIPSO IIR Cloud Data Products

Résumé

The Imaging Infrared Radiometer (IIR), one of the three instruments on board the CALIPSO satellite, includes three channels centered at 08.65 μm, 10.6 μm, and 12.05 μm. The center of its 69-km swath is by design co-located with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) ground track. Following the release of the Version 4 (V4) CALIOP data products, V4 IIR Level 2 data products are now available. The retrievals are applied to suitable types of scenes classified using the CALIOP 5-km cloud and aerosol layer products. IIR cloud microphysical retrievals use the concept of microphysical index (βeff) applied to the IIR pairs of channels (12.05, 10.6) and (12.05, 8.65), with βeff12/10 and βeff12/08 defined as the 12.05-to-10.6 and 12.05-to-08.65 ratios of the effective absorption optical depths, respectively. The key IIR retrievals are cloud effective emissivity in each IIR channel and the subsequent microphysical indices, which are interpreted in terms of effective diameter (De) by using Look-Up Tables (LUTs) built using the FASDOM model. For ice clouds, V4 uses two crystal models, namely severely rough "single hexagonal column" and "8-element column aggregate", and bulk scattering properties are computed using a gamma particle size distribution (PSD). De is retrieved using the ice crystal model that provides the best agreement with IIR "observations" in terms of relationship between βeff12/10 and βeff12/08. We show that modeled and observed βeff12/10-βeff12/08 relationships compare better in V4 than in V3, owing to the reduction of inter-channel biases in V4 effective emissivity retrievals. The "single hexagonal column" model is selected in 70 % of the cases for clouds of radiative temperature smaller than 200 K and this fraction steadily decreases to 60 % as radiative temperature increases up to 230 K, while the CALIOP particulate depolarization ratio exhibits similar relative variations with temperature. The cloud model selection is little sensitive to the assumed PSD, but sensitivity of retrieved De can be significant, as will be shown and discussed. Because the technique is very sensitive to small cloud particles, it is potentially well adapted for retrievals in liquid water clouds. Liquid water clouds microphysical properties, now available in the V4 IIR products, will be presented and discussed.

Domaines

Météorologie
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Dates et versions

insu-04485667 , version 1 (01-03-2024)

Identifiants

Citer

Anne Garnier, Jacques Pelon, N. Pascal, P. Dubuisson, P. Yang, et al.. Introducing the Version 4 CALIPSO IIR Cloud Data Products. American Geophysical Union, Fall Meeting 2019, Dec 2019, San Francisco, United States. pp.abstract #A11B-08. ⟨insu-04485667⟩
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