Titre :

A variational approach for retrieving ice cloud properties from infrared measurements: application in the context of two IIR validation campaigns

Auteur(s) :

Sourdeval, Odran [Auteur]
Laboratoire d'Optique Atmosphérique (LOA) - UMR 8518
Couillard Labonnotte, Laurent [Auteur]
Laboratoire d'Optique Atmosphérique (LOA) - UMR 8518
Brogniez, Gerard [Auteur]
Laboratoire d'Optique Atmosphérique (LOA) - UMR 8518
Jourdan, O. [Auteur]
Pelon, Jacques [Auteur]
Garnier, Anne [Auteur]

Titre de la revue :

Atmospheric Chemistry and Physics

Nom court de la revue :

Atmos. Chem. Phys.

Numéro :

13

Pagination :

8229-8244

Éditeur :

Copernicus GmbH

Date de publication :

2013-08-21

ISSN :

1680 7324

Discipline(s) HAL :

Physique [physics]/Physique [physics]/Physique Atmosphérique et Océanique [physics.ao-ph]
Planète et Univers [physics]/Sciences de la Terre/Climatologie
Sciences de l'environnement/Milieux et Changements globaux

Résumé en anglais : [en]

Cirrus are cloud types that are recognized to have a strong impact on the Earth-atmosphere radiation balance. This impact is however still poorly understood, due to the difficulties in describing the large variability of ...
Lire la suite >Cirrus are cloud types that are recognized to have a strong impact on the Earth-atmosphere radiation balance. This impact is however still poorly understood, due to the difficulties in describing the large variability of their properties in global climate models. Consequently, numerous airborne and space-borne missions have been dedicated to their study in the last decades. The satellite constellation A-Train has for instance proven to be particularly helpful for the study of cirrus. More particularly, the Infrared Imaging Radiometer (IIR) carried onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite shows a great sensitivity to the radiative and microphysical properties of these clouds. Our study presents a novel methodology that uses the thermal infrared measurements of IIR to retrieve the ice crystal effective size and optical thickness of cirrus. This methodology is based on an optimal estimation scheme, which possesses the advantage of attributing precise uncertainties to the retrieved parameters. Two IIR airborne validation campaigns have been chosen as case studies for illustrating the results of our retrieval method. It is observed that optical thicknesses could be accurately retrieved but that large uncertainties may occur on the effective diameters. Strong agreements have also been found between the products of our method when separately applied to the measurements of IIR and of the airborne radiometer CLIMAT-AV, which consolidates the results of previous validation studies of IIR level-1 measurements. Comparisons with in situ observations and with operational products of IIR are also discussed and appear to be coherent with our results. However, we have found that the quality of our retrievals can be strongly impacted by uncertainties related to the choice of a pristine crystal model and by poor constraints on the properties of possible liquid cloud layers underneath cirrus. Simultaneous retrievals of liquid clouds radiative and microphysical properties and/or the use of different ice crystal models should therefore be considered in order to improve the quality of the results.Lire moins >

Langue :

Anglais

Comité de lecture :

Oui

Audience :

Internationale

Vulgarisation :

Non

Établissement(s) :

Université de Lille
CNRS

Collections :

• Laboratoire d'Optique Atmosphérique (LOA) - UMR 8518

Équipe(s) de recherche :

Interactions Rayonnement Nuages (IRN)

Date de dépôt :

2023-01-06T14:22:29Z
2023-01-10T15:33:43Z
2023-01-11T13:16:22Z