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
Determination of standards for a UV-B monitoring network
1991 - 1994

Sujets :
Safety, Environmental Protection
Participants :
Laboratoire d'Optique Atmosphèrique
Laboratoire d'Optique Atmosphèrique


Department of Meteorology
Department of Meteorology


Belgian Institute for Space Aeronomy
Belgian Institute for Space Aeronomy


Aristotle University of Thessaloniki
Aristotle University of Thessaloniki


Natural Environment Research Council
Natural Environment Research Council


University of Cambridge
University of Cambridge


University of Tromsø
University of Tromsø


Koninklijk Nederlands Meteorologisch Instituut
Koninklijk Nederlands Meteorologisch Instituut


Leopold-franzens-universitaet Innsbruck
Leopold-franzens-universitaet Innsbruck


Universitaet Fuer Bodenkultur Wien
Universitaet Fuer Bodenkultur Wien


ARISTOTLE UNIVERSITY OF THESSALONIKI HELLAS
ARISTOTLE UNIVERSITY OF THESSALONIKI
Education

DEPARTMENT OF PHYSICS LABORATORY OF ATMOSPHERIC PHYSICS PO Box 149 Aristotle University of Thessaloniki 54006
HELLAS
University of Tromsø NORGE
University of Tromsø
Education

Institute of Mathematical and Physical Sciences 9037
NORGE
NATURAL ENVIRONMENT RESEARCH COUNCIL UNITED KINGDOM
NATURAL ENVIRONMENT RESEARCH COUNCIL
Research,Other

BRITISH ANTARCTIC SURVEY Madingley Road, High Cross CB3 0ET
UNITED KINGDOM
Koninklijk Nederlands Meteorologisch Instituut NEDERLAND
Koninklijk Nederlands Meteorologisch Instituut
Non Commercial

Division of Physical Meterology PO Box 201 3730 AE
NEDERLAND
University of Cambridge UNITED KINGDOM
University of Cambridge
Education

Department of Botany Downing Street CB2 3ET
UNITED KINGDOM
LEOPOLD-FRANZENS-UNIVERSITAET INNSBRUCK ÖSTERREICH
LEOPOLD-FRANZENS-UNIVERSITAET INNSBRUCK
Education

INSTITUTE OF MEDICAL PHYSICS 44,Müllerstrasse 44 6020
ÖSTERREICH
UNIVERSITAET FUER BODENKULTUR WIEN ÖSTERREICH
UNIVERSITAET FUER BODENKULTUR WIEN
Education,Other

INSTITUT FÜR METEOROLOGIE UND PHYSIK 18,Turkenschanzstrasse 18 1180
ÖSTERREICH
Hide objectives
The overall objective of this project is to produce practical recommendations for the deployment of an integrated ultraviolet B(UVB) network throughout Europe.
Hide achievements
The main results of these campaigns are summarised below 1. Good calibration procedures are a necessary first step for accurate and reliable measurements. Careful monitoring of the lamp current ensures consistency of the calibration source, the lamp-spectrometer geometry must be rigorously maintained, and stray light within the calibration room must be excluded. 2. The spectrometer geometry and mechanical stability must allow the calibration to remain valid between the fixed conditions of the calibration room and the different instrument orientations, spatial distributions of radiation and ambient conditions in the environment. In most cases this involves at least a temperature stabilisation of sensitive parts of the spectrometer. 3. Important characteristics of the ideal spectrometer are: (a) wavelength specification. This could be achieved to an accuracy of about 0.1 to 0.3nm in many of the instruments and is acceptable unless very accurate work in the short wavelength UV-B region of the spectrum is required. (b) slit function. This determines the near field stray light from adjacent wavelengths which is attributed to the nominated wavelength of a measurement. The slit function is important where the measured spectrum changes very rapidly with wavelength, as with solar UV-B. Measuring the slit function of the spectrometers allowed the effects of different slit functions on a measurement of the sun light to be calculated. Correcting for both slit function and wavelength specification improves the comparison between instruments, especially in the UV-B. (c) far-field stray light. Radiation from wavelengths outside the region of the slit function must be rigorously excluded. if not, it provides a background measurement which limits the sensitivity of the spectroradiometer. As the solar spectrum changes by three orders of magnitude across the UV-B regions, spectrometers need stray light rejection of the same order. In general the single monochromator and diode array instruments did not have sufficient stray light rejection for measurements at the shorter UV-B wavelengths. (d) cosine response. The fore optics of each spectrometer should have a cosine response but in practice this was often far from perfect. Asymmetry in the cosine response can lead to apparent diurnal asymmetry in the measured irradiances, and different cosine errors can add to discrepancies in response between instruments. Knowing the cosine response of an instrument allows corrections to be made, but these involve assumptions about the spectral distribution of the incident radiation. In conclusion, a group of UV spectrometers has been identified which could act together to form a UV network. Other instruments require some improvement in design or operational procedures, but could achieve the level of performance set by the core group. The experiences of the campaigners have led to a greater understanding of instrument and operational requirements, which will aid newcomers to this area of research and point the way to future improvements in hardware and methodologies. A transportable lamp system has been designed and built to maintain an independent check of calibrations when instruments are isolated at their home sites.

Source : Cordis  

Correction of the stratospheric aerosol radiative influence in the POLDER measurements
1998
Auteurs : M. HERMAN, B. LAFRANCE et TAT SOON YEO
Masquer le résumé
This paper presents the principles and performances of the stratospheric aerosol correction schemes for the Polarization and Directionality of the Earth's Reflectances (POLDER) spatial polarimeter measurements and the method used to derive, from the Stratospheric Aerosol and Gas Experiment II (SAGE II) data, the information about the aerosols that is needed for the correction. On the Advanced Earth Observing Satellite (ADEOS) platform since August 1996, POLDER performs multidirectional measurements, both of reflectance and of polarization in visible and near-infrared spectral bands. These new observational capabilities are used to observe clouds, lands, ocean surfaces, and tropospheric aerosols. These observations are weakly perturbed by the stratospheric aerosols, whose amount is currently low, but in the case of a major volcanic eruption, would increase strongly for few years. The possibility of such a situation has to be considered. Moreover, even near background conditions, the stratospheric aerosols perturb accurate retrieval of the ocean color and products deduced from the polarized light. That is why a systematic correction of their influence on the measured signal has been developed.
Keywords :
Stratosphere ; Stratospheric aerosol ; Atmospheric correction ; Radiative properties ; Polarimetry ; Satellite observation ; Performance ;
Source : Pascal - INIST  

Determination of the wind speed threshold for the emission of desert dust using satellite remote sensing in the thermal infrared
1999
Auteurs : O. CHOMETTE, M. Legrand, B. MARTICORENA et Béatrice Marticoréna
Masquer le résumé
The Infrared Difference Dust Index (IDDI), derived from images obtained from the Meteosat 10.5- to 12.5-μm channel, describes the dust distribution over the Saharan-Sahelian region. This IDDI, associated with the 10-m wind speed reanalyses from the European Centre for Mediurn-Range Weather Forecasts (ECMWF), reveals whether or not the observed dust is associated with emission from an underlying source. This result allows one to determine the wind speed thresholds for dust emission from targets located in the western, central, and eastern Saharan-Sahelian region, by means of satellite remote sensing. Threshold values determined for seven targets are presented. A comparison is carried out between such values and direct determinations obtained through the description of the soil texture and surface roughness of these targets. The agreement between these quite independent determinations is conclusive, with an average difference of 0.3 m s-1 and a rms difference of 0.35 m s-1.
Keywords :
Atmospheric dust ; Desert ; Wind velocity ; Satellite observation ; Image analysis ; Space remote sensing ; Ground surface ; Roughness ; Texture ; Sahara ; Sahel ; Meteosat satellites ; Africa ;
Source : Pascal - INIST  

Global observation of anthropogenic aerosols from satellite
2001
Auteurs : F.-M. BREON, J.-L. Deuzé, M. HERMAN, A. MARCHAND, F. NADAL, Goloub PHILLIPPE et Didier TANRE
Masquer le résumé
This paper provides the first climatology from satellite of aerosol loading, both over land and oceanic surfaces. Over land, aerosol loading is retrieved using a new remote sensing technique based on the polarization signature of scattered solar radiances. The product is sensitive to particles that are within the accumulation mode, smaller than ≃ 0.5μm. Those are mainly produced by anthropogenic sources, like smoke and urban/industrial aerosols. A rough identification of aerosol origin is obtained from the concomitant detection of fires from spaceborne observations. The combination of aerosol load and fire identification suggests that biomass burning is the main source of small particles in the atmosphere and that, at the regional scale, other anthropogenic activities have a significant impact limited to China and India.
Keywords :
Long-range transport ; Sea surface ; Satellite observation ; Anthropogenic factor ; Vegetation fire ; Radiance ; Polarization ; Space remote sensing ; Ground surface ; Climatology ; Aerosols ;
Source : Pascal - INIST  

Uncertainties in assessing radiative forcing by mineral dust
1998
Auteurs : Y. Balkanski, Yves Balkanski, Olivier Boucher, T. CLAQUIN, T. Claquin et M. Schulz
Masquer le résumé
The assessment of the climatic effects of an aerosol with a large variability like mineral dust requires some approximations whose validity is investigated in this paper. Calculations of direct radiative fordng by mineral dust (short-wave, long-wave and net) are performed with a single-column radiation model for two standard cases in clear sky condition: a desert case and an oceanic case. Surface forcing result from a large diminution of the short-wave fluxes and of the increase in down-welling long-wave fluxes. Top of the atmosphere (TOA) forcing is negative when short-wave backscattering dominates, for instance above the ocean, and positive when short-wave or long-wave absorption dominates, which occurs above deserts. We study here the sensitivity of these mineral forcings to different treatments of the aerosol complex refractive index and size distribution. We also describe the importance of the dust vertical profile, ground temperature, emissivity and albedo. Among these parameters, the aerosol complex refractive index has been identified as a critical parameter given the paucity and the incertitude associated with it. Furthermore, the imaginary part of the refractive index is inadequate if spectrally averaged. Its natural variability (linked to mineralogical characteristics) lead to variations of up to ± 40% in aerosol forcing calculations. A proper representation of the size distribution when modelling mineral aerosols is required since dust optical properties are very sensitive to the presence of small particles. In addition we demonstrate that LW forcing imply a non-negligible sensitivity to the vertical profiles of temperature and dust, the latter being an important constraint for dust effect calculations.
Keywords :
Aerosols ; Atmospheric dust ; Desert ; Radiative properties ; Effect on climate ; Clear sky ; Numerical simulation ; Refraction index ; Particle size distribution ; Sensitivity analysis ; Uncertainty ;
Source : Pascal - INIST  

Remote sensing of aerosols over land surfaces from POLDER-ADEOS-1 polarized measurements
2001
Auteurs : F.-M. BREON, Francois-Marie Breon, C. DEVAUX, J.-L. Deuzé, M. HERMAN, B. Lafrance, B. Lafrance, F. MAIGNAN, A. MARCHAND, F Maignan, F. NADAL, F. NADAL, G. PERRY, Goloub PHILLIPPE et Didier TANRE
Masquer le résumé
The polarization measurements achieved by the POLDER instrument on ADEOS-1 are used for the remote sensing of aerosols over land surfaces. The key advantage of using polarized observations is their ability to systematically correct for the ground contribution, whereas the classical approach using natural light fails. The estimation of land surface polarizing properties from POLDER has been examined in a previous paper. Here we consider how the optical thickness δ0 and Ångström exponent a of aerosols are derived from the polarized light backscattered by the particles. The inversion scheme is detailed, and illustrative results are presented. Maps of the retrieved optical thickness allow for detection of large aerosol features, and in the case of small aerosols, the δ0 and a retrievals are consistent with correlative ground-based measurements. However, because polarized light stems mainly from small particles, the results are biased for aerosol distributions containing coarser modes of particles. To overcome this limitation, an aerosol index defined as the product AI = δ0α is proposed. Theoretical analysis and comparison with ground-based measurements suggest that AI is approximately the same when using δ0, and a is related to the entire aerosol size distribution or derived from the polarized light originating from the small polarizing particles alone. This invariance is specially assessed by testing the continuity of Al across coastlines, given the unbiased properties of aerosol retrieval over ocean. Although reducing the information concerning the aerosols, this single parameter allows a link between the POLDER aerosol surveys over land and ocean. POLDER aerosol index global maps enable the monitoring of major aerosol sources over continental areas.
Keywords :
Space remote sensing ; Aerosols ; Ground surface ; Polarization ; Polarized light ; Optical thickness ; Particle size distribution ; Monitoring ; Satellite observation ; Backscattering ; ADEOS satellite ;
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


Centre National de la Recherche Scientifique
Centre National de la Recherche Scientifique


Commission of the European Communities
Commission of the European Communities


University of Crete
University of Crete


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  





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