Title :

An algorithm to retrieve ice water content profiles in cirrus clouds from the synergy of ground-based lidar and thermal infrared radiometer measurements

Author(s) :

Hemmer, Friederike [Auteur]
Laboratoire d’Optique Atmosphérique - UMR 8518 [LOA]
Couillard-Labonnotte, Laurent [Auteur]
Laboratoire d'Optique Atmosphérique (LOA) - UMR 8518
Parol, Frederic [Auteur]
Laboratoire d'Optique Atmosphérique (LOA) - UMR 8518
Brogniez, Gerard [Auteur]
Laboratoire d'Optique Atmosphérique (LOA) - UMR 8518
Damiri, Bahaiddin [Auteur]
Podvin, Thierry [Auteur]
Laboratoire d’Optique Atmosphérique - UMR 8518 [LOA]

Journal title :

Atmospheric Measurement Techniques

Abbreviated title :

Atmos. Meas. Tech.

Volume number :

12

Publication date :

2019-03-12

ISSN :

1867-1381

HAL domain(s) :

Physique [physics]

English abstract : [en]

The algorithm presented in this paper was developed to retrieve ice water content (IWC) profiles in cirrus clouds. It is based on optimal estimation theory and combines ground-based visible lidar and thermal infrared (TIR) ...
Show more >The algorithm presented in this paper was developed to retrieve ice water content (IWC) profiles in cirrus clouds. It is based on optimal estimation theory and combines ground-based visible lidar and thermal infrared (TIR) radiometer measurements in a common retrieval framework in order to retrieve profiles of IWC together with a correction factor for the backscatter intensity of cirrus cloud particles. As a first step, we introduce a method to retrieve extinction and IWC profiles in cirrus clouds from the lidar measurements alone and demonstrate the shortcomings of this approach due to the backscatter-to-extinction ambiguity. As a second step, we show that TIR radiances constrain the backscattering of the ice crystals at the visible lidar wavelength by constraining the ice water path (IWP) and hence the IWC, which is linked to the optical properties of the ice crystals via a realistic bulk ice microphysical model. The scattering phase function obtained from the microphysical model is flat around the backscatter direction (i.e., there is no backscatter peak). We show that using this flat backscattering phase function to define the backscatter-to-extinction ratio of the ice crystals in the retrievals with the lidar-only algorithm results in an overestimation of the IWC, which is inconsistent with the TIR radiometer measurements. Hence, a synergy algorithm was developed that combines the attenuated backscatter profiles measured by the lidar and the measurements of TIR radiances in a common optimal estimation framework to retrieve the IWC profile together with a correction factor for the phase function of the bulk ice crystals in the backscattering direction. We show that this approach yields consistent lidar and TIR results. The resulting lidar ratios for cirrus clouds are found to be consistent with previous independent studies.Show less >

Language :

Anglais

Peer reviewed article :

Oui

Audience :

Internationale

Popular science :

Non

Administrative institution(s) :

CNRS
Université de Lille

Collections :

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

Submission date :

2024-01-30T11:45:48Z
2024-02-26T16:00:26Z