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
High spectral resolution remote sensing for earth's weather and climate studies
1993 - 1995

Sujets :
Coordination, Cooperation, Education, Training
Participants :
Laboratoire de Météorologie Dynamique
Laboratoire de Météorologie Dynamique


Laboratoire d'Optique Atmosphèrique
Laboratoire d'Optique Atmosphèrique


FREIE UNIVERSITAET BERLIN DEUTSCHLAND
FREIE UNIVERSITAET BERLIN
Education

INSTITUT FUER WELTRAUMWISSENSCHAFTEN (WE4) - FACHBEREICH GEOWISSENSCHAFTEN Fabeckstrasse 69 14195
DEUTSCHLAND
COUNCIL FOR THE CENTRAL LABORATORY OF THE RESEARCH COUNCILS UNITED KINGDOM
COUNCIL FOR THE CENTRAL LABORATORY OF THE RESEARCH COUNCILS
Research,Other

RUTHERFORD APPLETON LABORATORIES Chilton OX11 0QX
UNITED KINGDOM
UNIVERSITE PIERRE ET MARIE CURIE - PARIS VI FRANCE
UNIVERSITE PIERRE ET MARIE CURIE - PARIS VI
Education

SERVICE D'ARONOMIE PO Box 121 Place Jussieu 4 Tour 15 75230
FRANCE

Source : Cordis  

Comparison of OMI ozone and UV irradiance data with ground-based measurements at two French sites
2008
Auteurs : Frédérique Auriol, B. Bojkov, B. Bonnel, Colette Brogniez, V. Buchard, J. LENOBLE, Aapo TANSKANEN et Pepijn J. Veefkind
Masquer le résumé
Ozone Monitoring Instrument (OMI), launched in July 2004, is dedicated to the monitoring of the Earth's ozone, air quality and climate. OMI provides among other things the total column of ozone (TOC), the surface ultraviolet (UV) irradiance at several wavelengths, the erythemal dose rate and the erythemal daily dose. The main objective of this work is to validate OMI data with ground-based instruments in order to use OMI products (collection 2) for scientific studies. The Laboratoire d'Optique Atmosphérique (LOA) located in Villeneuve d'Ascq in the north of France performs solar UV measurements using a spectroradiometer and a broadband radiometer. The site of Briançon in the French Southern Alps is also equipped with a spectroradiometer operated by Interaction Rayonnement Solaire Atmosphère (IRSA). The instrument belongs to the Centre Européen Médical et Bioclimatologique de Recherche et d'Enseignement Supérieur. The comparison between the TOC retrieved with ground-based measurements and OMI TOC shows good agreement at both sites for all sky conditions. Comparisons of spectral UV on clear sky conditions are also satisfying whereas results of comparisons of the erythemal daily doses and erythemal dose rates for all sky conditions and for clear sky show that OMI overestimates significantly surface UV doses at both sites.
Keywords :
Source : HAL  

Numerical simulation of the 7 to 9 September 2006 AMMA mesoscale convective system: Evaluation of the dynamics and cloud microphysics using synthetic observations
2010
Auteurs : Dominique Bouniol, S. Cautenet, Philippe DUBUISSON, C. Duroure, Vincent Giraud, Alain PROTAT et Guillaume Penide
Masquer le résumé
This paper presents a numerical simulation of a Mesoscale Convective System (MCS) observed during the AMMA (African Monsoon Multidisciplinary Analysis) experiment with the BRAMS model (Brazilian Regional Atmospheric Modelling System). The aim is to document the life cycle of the MCS and to identify key cloud microphysical processes and their signatures by making use of synthetic observations calculated from the simulated fields. These observations: ARM (Atmospheric Radiation Measurement) 95 GHz equivalent radar reflectivity factor and Doppler velocity and infrared brightness temperatures in three SEVIRI (Spinning Enhanced Visible and InfraRed Imager) channels centred at 8.7, 10.6 and 12 µm are simulated using respectively Mie scattering theory and FASDOM (Fast Discrete Ordinate Method), a fast radiative transfer code. Synthetic observations and model variables are compared to various measurements from several platforms (W-band and Massachusetts Institute of Technology (MIT) ground-based Doppler radars, soundings, aircraft measurements, and Meteosat Second Generation) to evaluate the model at different scales and to identify the signatures of microphysical properties with a focus on the anvil part of the MCS. A method using both the ARM and the MIT radar data is used to identify the different regimes within the MCS. A relatively good agreement with direct comparisons is found, as well as discrepancies in the microphysical scheme parametrization that clearly need improvements (using in situ measurements). Microphysical signatures are also studied using joint radar reflectivity/Doppler-height histograms. Their analysis shows that the model tends to overplay the role of the riming processes, even in the anvil part of the MCS. Comparisons of the Particle Size Distributions (simulated and measured in situ) show the model's ability to reproduce complex PSDs (e.g. a multimodal behaviour)
Keywords :
Source : HAL  

Global aerosol climatology from the MODIS satellite sensors
2008
Auteurs : Brent N. HOLBEN, HONGBIN YU, Charles ICHOKU, Yoram J. KAUFMAN, Richard G. KLEIDMAN, Ilan KOREN, Robert C. LEVY, Shana MATTOO, Lorraine A. REMER, Didier TANRE et José VANDERLEI MARTINS
Masquer le résumé
[1] The recently released Collection 5 Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol products provide a consistent record of the Earth's aerosol system. Comparing with ground-based AERONET observations of aerosol optical depth (AOD) we find that Collection 5 MODIS aerosol products estimate AOD to within expected accuracy more than 60% of the time over ocean and more than 72% of the time over land. This is similar to previous results for ocean and better than the previous results for land. However, the new collection introduces a 0.015 offset between the Terra and Aqua global mean AOD over ocean, where none existed previously. Aqua conforms to previous values and expectations while Terra is higher than what had been expected. The cause of the offset is unknown, but changes to calibration are a possible explanation. Even though Terra's higher ocean AOD is unexpected and unexplained, we present climatological analyses of data from both sensors. We find that the multiannual global mean AOD at 550 nm over oceans is 0.13 for Aqua and 0.14 for Terra, and over land it is 0.19 in both Aqua and Terra. AOD in situations with 80% cloud fraction are twice the global mean values, although such situations occur only 2% of the time over ocean and less than 1% of the time over land. Aerosol particle size associated with these very cloudy situations does not show a drastic change over ocean, but does over land. Regionally, aerosol amounts vary from polluted areas such as east Asia and India, to the cleanest regions such as Australia and the northern continents. As AOD increases over maritime background conditions, fine mode aerosol dominates over dust over all oceans, except over the tropical Atlantic downwind of the Sahara and during some months over the Arabian Sea.
Keywords :
Indian Ocean ; Africa ; Atlantic Ocean ; Australasia ; Arabian Sea ; Sahara ; Equatorial Atlantic ; Australia ; India ; dust ; fine-grained materials ; continents ; Asia ; Particle size ; Cloud fraction ; calibration ; accuracy ; Optical thickness ; Earth ; collections ; satellites ; Climatology ; aerosols ; global ;
Source : Pascal - INIST  

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 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  

Comparison of High-Cloud Characteristics as Estimated by Selected Spaceborne Observations and Ground-Based Lidar Datasets
2009
Auteurs : Gérard BROGNIEZ, Patrick CHERVET, Martial HAEFFELIN, Martial HAEFFELIN, Olga LADO-BORDOWSKY, Yohann MORILLE, Yohann Morille, Frédéric PAROL, Jacques PELON, Artemio PLANA-FATTORI, Antoine Roblin, Geneviève SEZE, Claudia STUBENRAUCH, Claudia STUBENRAUCH et G. Sèze
Masquer le résumé
The characterization of high clouds as performed from selected spaceborne observations is assessed in this article by employing a number of worldwide ground-based lidar multiyear datasets as reference. Among the latter, the ground lidar observations conducted at Lannion, Bretagne (48.7°N, 3.5°W), and Palaiseau, near Paris [the Site Instrumental de Recherche par Télédétection Atmosphérique (SIRTA) observatory: 48.7°N, 2.2°E], both in France, are discussed in detail. High-cloud altitude statistics at these two sites were found to be similar. Optical thicknesses disagree, and possible reasons were analyzed. Despite the variety of instruments, observation strategies, and methods of analysis employed by different lidar groups, high-cloud optical thicknesses from the Geoscience Laser Altimeter System (GLAS) on board the Ice, Cloud and land Elevation Satellite (ICESat) were found to be consistent on the latitude band 40°-60°N. Respective high-cloud altitudes agree within 1 km with respect to those from ground lidars at Lannion and Palaiseau; such a finding remains to be verified under other synoptic regimes. Mean altitudes of high clouds from Lannion and Palaiseau ground lidars were compared with altitudes of thin cirrus from the Television and Infrared Observation Satellite (TIROS) Operational Vertical Sounder (TOVS) Path-B 8-yr climatology for a common range of optical thicknesses (0.1-1.4). Over both sites, the annual altitude distribution of thin high clouds from TOVS Path-B is asymmetric, with a peak around 8-9.5 km, whereas the distribution of high clouds retrieved from ground lidars seems symmetric with a peak around 9.5-11.5 km. Additional efforts in standardizing ground lidar observation and processing methods, and in merging high-cloud statistics from complementary measuring platforms, are recommended.
Keywords :
TIROS operational vertical sounder ; Polar orbiting satellite ; Space remote sensing ; statistical analysis ; Altitudinal distribution ; Climatology ; Remote sensing by laser beam ; Radar altimetry ; altimetry ; Lidar ; Ground based measurement ; Radar observation ; TIROS satellites ; Satellite observation ; Measurement technique ; High altitude ; clouds ;
Source : Pascal - INIST  





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