Title :

An improved algorithm of cloud droplet size distribution from polder polarized measurements

Author(s) :

Shang, Huazhe [Auteur]
Laboratoire d’Optique Atmosphérique - UMR 8518 [LOA]
Chinese Academy of Sciences [Beijing] [CAS]
Letu, Husi [Auteur]
Tokai University
Chinese Academy of Sciences [Beijing] [CAS]
Breon, Francois-Marie [Auteur]
Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] [LSCE]
Riedi, Jerome [Auteur]
Laboratoire d’Optique Atmosphérique - UMR 8518 [LOA]
interaction Clouds Aerosols Radiations - ICARE/AERIS Data and Services Center - UMS 2877 [ICARE]
Ma, Run [Auteur]
University of Chinese Academy of Sciences [Beijing] [UCAS]
Chinese Academy of Sciences [Beijing] [CAS]
Wang, Ziming [Auteur]
University of Chinese Academy of Sciences [Beijing] [UCAS]
Chinese Academy of Sciences [Beijing] [CAS]
Nakajima, Takashi Y. [Auteur]
Tokai University
Wang, Zhongting [Auteur]
Chen, Liangfu [Auteur]
Chinese Academy of Sciences [Beijing] [CAS]

Journal title :

Remote Sensing of Environment

Abbreviated title :

Remote Sens. Environ.

Volume number :

228

Publication date :

2019-07-01

ISSN :

0034-4257

English keyword(s) :

POLDER
Cloud droplet radius
Droplet effective variance
Polarization
Droplet size retrieval

HAL domain(s) :

Physique [physics]

English abstract : [en]

The Polarization and Directionality of Earth Reflectances (POLDER) instrument provides unique cloud droplet radius (CDR) and effective variance (EV) observations for the analysis of clouds on the global scale. However, the ...
Show more >The Polarization and Directionality of Earth Reflectances (POLDER) instrument provides unique cloud droplet radius (CDR) and effective variance (EV) observations for the analysis of clouds on the global scale. However, the cloud droplet size distribution estimated using the conventional POLDER algorithm is limited by its coarse spatial resolution (150 km) and insufficient information for large droplets (CDR > 15 μm). In this study, we proposed an improved primary cloudbow retrieval (PCR) algorithm to estimate CDR and EV from POLDER. Simulated retrievals based on a radiative transfer model indicate that primary cloudbow measurements are sensitive to large droplets (CDR > 15 μm) and enable the retrieval to be applied at a higher spatial resolution; therefore, we employ POLDER polarized measurements from both primary and supernumerary cloudbow regions in the PCR algorithm. Retrieval cases using POLDER measurements reveal that the PCR algorithm is robust when the cloud fields are homogeneous. When the cloud field is heterogeneous, the estimation of CDR is sensitive to the scattering angle ranges as well as the grid size, with uncertainty <1 μm. In addition, a spatial resolution of 40–60 km is suitable for the PCR algorithm based on the relationship between the retrieval grid size and the total successful retrievals. Further comparisons between the PCR retrievals and operational products are conducted on the global scale using POLDER measurements for February, May, August and November 2008, revealing that PCR retrievals agree well with operational products on the global scale as CDR < 15 μm. Our analysis indicates that most of the large droplets estimated using the conventional procedure are overestimated due to the absence of primary cloudbow measurements. The PCR algorithm permits an extended range of CDR (3–25 μm) and EV (0.01–0.29) estimates and a higher resolution (40–60 km) in the retrieval.Show less >

Language :

Anglais

Audience :

Internationale

Popular science :

Non

Administrative institution(s) :

CNRS
Université de Lille

Collections :

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

Submission date :

2024-01-30T11:45:52Z
2024-02-21T09:51:52Z
2024-02-23T14:19:17Z