Cloud parameter retrieval from combined remote sensing observations

• Published in: Physics and chemistry of the earth. Part B, Hydrology, oceans and atmosphere Vol. 25; no. 10-12; pp. 1063 - 1067
• Main Authors: Tinel, C, Testud, J, Guyot, A, Caillault, K
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 2000
• ISSN: 1464-1909
• DOI: 10.1016/S1464-1909(00)00153-2

To appreciate the radiative impact of clouds in the dynamics of the global atmosphere, it is important to deploy from space, from aircraft, or from ground, instruments able to describe the cloud layering and to document the cloud characteristics (namely liquid and/or ice water content, and the effective particle radius). Combining passive and active remote sensing techniques, microwave or VIS/IR, is a possible way to achieve this goal. A statistical knowledge of particle spectra drawn from microphysical data base is nevertheless indispensable to build the inverse model and algorithms needed to retrieve the cloud parameters from remote sensing observations. The present paper covers three subjects: •- Techniques to analyse particle spectra from cloud databases: What are the key parameters to characterise a particle spectrum? What are their statistics? How do they vary with temperature?•- Building of the inverse model: How do the parameters which define the response of remote sensing instruments (radar reflectivity Z, radar specific attenuation K, lidar backscattering coefficient β, lidar extinction coefficient α) relate to the cloud parameters interesting to evaluate cloud radiative properties (liquid water content LWC, ice water content IWC, effective radius of particles ree.•- Algorithm retrieval: What are the uncertainties in the retrievals of radar or lidar alone? What do combined observations of radar and lidar bring? What kind of combined algorithm can we consider to improve the retrieval? Results of the combining algorithm applied tot data sets are then presented.