LOA - Laboratoire d'Optique Atmosphèrique - UMR 8518

France Centre de recherche public
Accréditation CIR
Contact principal
Téléphone : 33(0)3 20 43 45 32
Mail : direction-loa@univ-lille1.fr
Adresse :
Bât. P5
59655 Villeneuve d'Ascq
France
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Description
(Extrait du site web)
Activité Générale :

L'optique atmosphérique cherche à modéliser la propagation à travers l'atmosphère de la lumière visible reçue du soleil et de la lumière infrarouge émise par l'ensemble des surfaces et de l'atmosphère terrestres. Les travaux menés au LOA dans ce domaine s'insèrent dans l'étude globale du climat.

Un premier objectif est de quantifier le rôle de ce rayonnement visible et infrarouge dans les échanges énergétiques de la planète, en particulier de préciser le rôle des nuages dans le bilan radiatif de la terre dont ils constituent un facteur essentiel.

Un second axe de recherche porte sur la caractérisation à l'échelle du globe de différents paramètres qui sont en relation directe avec l'évolution climatique (nuages, aérosols, surfaces), en utilisant principalement l'observation satellitaire.
Les travaux menés dans ce contexte mettent en oeuvre:

* La conception de logiciels permettant de simuler le transfert du rayonnement, à l'aide de modèles du système terre - atmosphère.
* L'analyse d'observations acquises par les capteurs satellitaires existants, le plus souvent sous forme d'images traitées sur ordinateur, et la conception d'expériences satellitaires nouvelles.
* La réalisation de campagnes d'observation de terrain, utilisant des appareillages développés par le laboratoire, mis en oeuvre au sol ou à partir d'avions ou de ballons stratosphériques, et destinés à valider les modèles ou à mettre en évidence les processus atmosphériques.

Le LOA est une unité Mixte de Recherches (UMR/CNRS 8518). Il fait partie de la Fédération de Recherches (FR1818) Milieux naturels et anthropisé Flux et dynamique.

Quelques documents de Laboratoire d'Optique Atmosphèrique
Retrieval of the scattering and microphysical properties of aerosols from ground-based optical measurements including polarization. I. Method.
2000
Auteurs : C. DEVAUX, M. HERMAN et A. VERMEULEN
Masquer le résumé
A method has been developed for retrieving the scattering and microphysical properties of atmospheric aerosol from measurements of solar transmission, aureole, and angular distribution of the scattered and polarized sky light in the solar principal plane. Numerical simulations of measurements have been used to investigate the feasibility of the method and to test the algorithm's performance. It is shown that the absorption and scattering properties of an aerosol, i.e., the single-scattering albedo, the phase function, and the polarization for single scattering of incident unpolarized light, can be obtained by use of radiative transfer calculations to correct the values of scattered radiance and polarized radiance for multiple scattering, Rayleigh scattering, and the influence of ground. The method requires only measurement of the aerosol's optical thickness and an estimate of the ground's reflectance and does not need any specific assumption about properties of the aerosol. The accuracy of the retrieved phase function and polarization of the aerosols is examined at near-infrared wavelengths (e.g., 0.870 mum). The aerosol's microphysical properties (size distribution and complex refractive index) are derived in a second step. The real part of the refractive index is a strong function of the polarization, whereas the imaginary part is strongly dependent on the sky's radiance and the retrieved single-scattering albedo. It is demonstrated that inclusion of polarization data yields the real part of the refractive index.

Atmospheric water vapor estimate by a differential absorption technique with the polarisation and directionality of the Earth reflectances (POLDER) instrument
1997
Auteurs : S. BOUFFIES, S. BOUFFIES, F.-M. BREON, Francois-Marie Breon, P. DUBUISSON et Didier TANRE
Masquer le résumé
The polarization and directionality of the Earth reflectances (POLDER) instrument, to be launched in 1996 on the Japanese ADEOS (advanced Earth observing satellite) platform includes a channel which covers the 910 nm water vapor absorption band (near IR), as well as a channel centered at 865 nm. An estimate of the total atmospheric water vapor content can be derived from the ratio of the two reflectance measurements. In addition to the spectroscopic parameterization, the major uncertainties of this estimate result from (1) the surface reflectance spectral signature, (2) scattering by atmospheric aerosol, and (3) the water vapor vertical profile. A radiative transfer model has been developed in order to quantify these uncertainties. From radiative transfer simulations an uncertainty on the order of 10% is expected on the total water vapor amount. An airborne version of the POLDER instrument has been developed and flown over various targets. These targets include semiarid surfaces (Sahel), bog, coniferous and deciduous forest (Boreal forest), and the ocean in the glint direction. Water vapor measurements from radiosondes, concomitant with the POLDER measurements, are available for the method validation. Over water bodies with glint present, an overestimate is found, which is still not understood at present. For other surfaces the comparisons are, in general, in good agreement with the uncertainty analysis.
Keywords :
Radiative transfer ; Vapor ; Water ; Uncertainty ; Ground surface ; Reflectance ; Aerosols ; Vertical profile ; Airborne instruments ;
Source : Pascal - INIST  

Particles of human origin extinguishing natural solar irradiance in climate systems
PHOENICS
2002 - 2005

Sujets :
Meteorology, Resources of the Sea, Fisheries, Environmental Protection, Forecasting
Participants :
Laboratoire d'Optique Atmosphèrique
Laboratoire d'Optique Atmosphèrique


Laboratoire des Sciences du Climat et de l'Environnement
Laboratoire des Sciences du Climat et de l'Environnement


Institute for Chemistry (otto Hahn Institute)
Institute for Chemistry (otto Hahn Institute)


Institute for Meteorology
Institute for Meteorology


UNIVERSITY OF CRETE HELLAS
UNIVERSITY OF CRETE
Education,Other

DEPARTMENT OF CHEMISTRY - SCHOOL OF SCIENCES ENVIRONMENTAL CHEMICAL PROCESSES LABORATORY Leoforos Knosou, Ampelokipi 71409
HELLAS
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE FRANCE
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
Research

URA 0713 - LABORATOIRE D'OPTIQUE ATMOSPHÉRIQUE Laboratoire d'Optique Atmosphérique (URA 713) UER de Physique Fondamentale Université de Lille 59655
FRANCE
UTRECHT UNIVERSITY NEDERLAND
UTRECHT UNIVERSITY
Other,Education

PO Box 80.125 8,HEIDELBERGLAAN 8 3508 TC
NEDERLAND
COMMISSION OF THE EUROPEAN COMMUNITIES ITALIA
COMMISSION OF THE EUROPEAN COMMUNITIES
Research

INSTITUTE FOR ENVIRONMENT AND SUSTAINABILITY ATMOSPHERIC PROCESSES IN GLOBAL CHANGE UNIT Via Enrico Fermi TP 290 21020
ITALIA
NATIONAL RESEARCH COUNCIL OF ITALY ITALIA
NATIONAL RESEARCH COUNCIL OF ITALY
Research,Other

ISTITUTO DI SCIENZE DELL'ATMOSFERA E DEL CLIMA Via P. Gobetti 101 40129
ITALIA
Hide objectives
PHOENICS is a global modelling project to study the direct climate effect of multi-component mixed troposphere aerosols. The potentially great climatic importance of aerosols urgently requires improvement of the estimates of the climate effect of aerosols and better evaluation of the associated uncertainties. Innovative size-resolved simulations of the distribution and properties of the mixture of all major aerosol components will be performed with a global 3-dimensional atmospheric general circulation model to assess the direct effect of aerosols. Several of the main uncertainties associated with this effect will be quantified and reduced by model improvement, comparison to selected observations and optimal use of satellite data. The impact of European emissions on the European and global environment and climate, and the influence of other world regions on Europe will be assessed focusing on the role of the Mediterranean.

Source : Cordis  

Cloud detection and derivation of cloud properties from POLDER
1997
Auteurs : Jean-Claude BURIEZ, B. Bonnel, P. Couvert, Pierre Couvert, Y. FOUQUART, M. HERMAN, Frédéric PAROL, Goloub PHILLIPPE, D. G. SEZE, D. G. SEZE et Claudine VANBAUCE
Masquer le résumé
POLDER (POLarization and Directionality of the Earth's Reflectances) is a new instrument devoted to the global observation of the polarization and directionality of solar radiation reflected by the Earth surface-atmosphere system. This radiometer has been on board the Japanese ADEOS platform since August 1996. This paper describes the main algorithms of the POLDER 'Earth radiation budget (ERB) & clouds' processing line used to derive products on a routine basis in the early phase of the mission. In addition to the bidirectional reflectance and polarization distribution functions, the main products will be the cloud optical thickness, pressure (from two different methods) and thermodynamic phase. Airborne POLDER observations support the present algorithms for the cloud detection and the derivation of cloud properties.
Keywords :
Clouds ; Satellite observation ; Solar radiation ; Algorithm ; Radiation polarization ; Reflectance ; Optical thickness ; Thermodynamic parameter ; Spaceborne instruments ;
Source : Pascal - INIST  

Analysis of direct comparison of cloud top temperature and infrared split window signature against independant retrievals of cloud thermodynamic phase
2001
Auteurs : V. GIRAUD, Goloub PHILLIPPE, Jérome RIEDI et O. THOURON
Masquer le résumé
An accurate determination of cloud particle phase is required for retrieval of other cloud properties. The main purpose of this letter is to demonstrate that the cloud phase assumption made in previous cirrus clouds retrievals using infrared split window signatures is not relevant. Coincident observations of the Earth surface from ERS-2 and ADEOS-1 satellites give us the opportunity to compare clouds infrared signatures, as observed by ATSR-2 onboard ERS-2, with cloud thermodynamic phase derived from POLDER onboard ADEOS-1. We find out, firstly, that large Brightness Temperature Differences (BTD), estimated between 11 and 12 μm, may occured for cold liquid water clouds consisting of small supercooled droplets (i.e. altostratus). These BTDs have no longer been attributed to cirrus clouds as previous studies have been. Secondly, the probability to observe ice or water clouds with respect to their cloud top temperature is quantified for our data set. A sharp transition between the ice and water phase is shown for cloud top temperatures ranging between 240 and 260 K. The probability for a cloud to be composed of super-cooled liquid droplets is shown to be higher over land than over ocean. This points out that ice activation susceptibility is more efficient in maritime air mass than in continental one.
Keywords :
Water cloud ; Cirrus ; Earth surface ; Brightness temperature ; Temperature difference ; Supercooled water ; Droplet ; Ice cloud ; Ice ; Air mass ; Satellite observation ; Infrared radiation ; ADEOS satellite ; ERS satellite ;
Source : Pascal - INIST  

Cirrus microphysical properties and their effect on radiation : survey and integration into climate models using combined satellite observations (CIRAMOSA)
CIRAMOSA
2001 - 2003

Sujets :
Measurement Methods, Environmental Protection, Resources of the Sea, Fisheries, Meteorology, Forecasting
Participants :
Laboratoire de Météorologie Dynamique
Laboratoire de Météorologie Dynamique


Laboratoire d'Optique Atmosphèrique
Laboratoire d'Optique Atmosphèrique


CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE FRANCE
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
Research

URA 0713 - LABORATOIRE D'OPTIQUE ATMOSPHÉRIQUE Laboratoire d'Optique Atmosphérique (URA 713) UER de Physique Fondamentale Université de Lille 59655
FRANCE
SECRETARY OF STATE FOR DEFENCE - MINISTRY OF DEFENCE UNITED KINGDOM
SECRETARY OF STATE FOR DEFENCE - MINISTRY OF DEFENCE
Research

METEOROLOGICAL OFFICE HADLEY CENTRE FOR CLIMATE PREDICTION AND RESEARCH Fitzroy Road, Metz Office EX1 3PB
UNITED KINGDOM
Hide objectives
The radiation effect due to changes of microphysical properties within cirrus clouds can be very important. We will provide a long-term survey of these properties, together with cirrus macrophysical properties, and then establish a compilation of correlations between them and the state of the atmosphere. This information is essential for the understanding of changes in clouds expected by a global climate change. Satellite instruments measuring radiation with a good spectral resolution as well as multi-angular measurements of polarized reflectance used with newly developed retrieval algorithms are now capable to give this information over the whole globe. Extensive care will be taken of the validation of the retrieved cirrus properties by intercomparison with data sets from regional measurement campaigns. Models for climate prediction can profit from the outcome of this proposal by using the most appropriate correlations in their radiation codes.

Source : Cordis  

Single-scattering albedo of smoke retrieved from the sky radiance and solar transmittance measured from ground : Smike, clouds, and radiation-Brazil
1998
Auteurs : Oleg DUBOVIK, B. N. Holben, Y. J. Kaufman, Ilya SLUTSKER, Alexander SMIRNOV, Didier TANRE et M. YAMASOE
Masquer le résumé
A method of aerosol single-scattering albedo retrieval from diffuse radiance measured in the solar almucantar and direct solar measurements is proposed. The aerosol scattering optical thickness is derived from the diffuse radiance by applying a radiative transfer model driven by aerosol microstructure parameters and Mie theory. To improve the accuracy of the scattering optical thickness, the inversion results are acceptable only if the radiance is measured across the total almucantar and is accurately fitted by a theoretical model. The aerosol is assumed as an external mixture of purely scattering particles and soot particles, with the soot approximated as a pure absorber. The criterion for the acceptance of fit is determined from the analysis of the effects of random and systematic errors on the single-scattering albedo retrieval. The method was applied to measurements conducted during the Smoke, Clouds, and Radiation - Brazil (SCAR-B) campaign in August and September 1995. Aerosol radiance data were extensively collected by the Aerosol Robotic Network (AERONET) of ground-based Sun/sky radiometers. The analysis focuses on the studies of the time variability of the biomass burning aerosol in the local Cuiabá area, supplemented by measurements collected in Cuiabá in 1993-1994. The results show reasonable ranges of the aerosol single-scattering albedo variability (for example, single-scattering albedo averages 0.87 ±0.08 at 670 nm). The spectral dependence of the single-scattering albedo has both tendencies: decreasing and increasing with wavelength. The potential reasons causing different spectral behavior are analyzed theoretically.
Keywords :
Aerosols ; Smoke emission ; Albedo ; Radiance ; Measurement method ; Optical thickness ; Error analysis ; Canopy fire ; Sensitivity analysis ; Brazil ; South America ; America ;
Source : Pascal - INIST  





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