Rita NOHRA
PhD in Physics, speciality Sciences de la Matière, du Rayonnement et de l'Environnement
Thesis defended on 21st March 2016
Laboratoire d'Optique Atmosphérique (LOA)

 


Title and thesis summary

Study of macrophysical and optical properties of cirrus clouds using a micro-lidar on the Lille site

Clouds are the main source of the uncertainty of climate studies (IPCC, 2013). Cirrus clouds are a special group of clouds, mainly composed of ice crystals, they cover about 30 % of the globe. Their high altitudes and the complexity of their microphysical properties make their characteristics poorly known. The impact of cirrus clouds is difficult to quantify, contributing to Earth's radiation budget with a relatively low albedo effect and a stronger greenhouse effect. Since 2006, LOA has an atmospheric monitoring station equipped with a ground-based micro-lidar and several passive instruments. The objective of this study is to retrieve cirrus clouds properties over Lille, using the micro-lidar database on the observation site in Lille. The first part of this thesis was to develop an algorithm for the detection and the characterization of cirrus clouds using the backscatter profiles measured by the micro-lidar. Seven years of observations have been treated with this algorithm, which allow us to establish a climatology of cirrus clouds over Lille site and to retrieve their macrophysical properties and microphysical properties. In addition, an application of this algorithm to the data obtained from a micro-lidar on M'bour (Senegal) site was performed in order to differentiate the characteristics of cirrus clouds observed at both sites. Finally, the results of the seven years of data on the Lille site were compared to those obtained by the lidar CALIOP on board CALIPSO platform showing an agreement between the two results.

Referees :
Philippe KECKHUT
Johannes QUAAS

Examiners :
Marjolaine CHIRIACO
Jacques PELON
Olivier JOURDAN

Supervisor :
Frédéric Parol (LOA)

Co-supervisor:
Philippe Dubuisson (LOA)

Laboratory: LOA

Financing: Region Nord-Pas-de-Calais / Université Lille 1