Characteristics of the UV radiation field in the Alps
Meteorology, Forecasting, Measurement Methods, Environmental Protection
Laboratoire d'Optique Atmosphèrique
Fraunhofer-gesellschaft Zur Foerderung Der Angewandten Forschung E.V.
Universitaet Fuer Bodenkultur Wien
Universite Joseph Fourier - Grenoble 1
Physikalisch-meteorologisches Observatorium Davos
LEOPOLD-FRANZENS-UNIVERSITAET INNSBRUCK ÖSTERREICH
FRAUNHOFER-GESELLSCHAFT ZUR FOERDERUNG DER ANGEWANDTEN FORSCHUNG E.V. DEUTSCHLAND
UNIVERSITAET FUER BODENKULTUR WIEN ÖSTERREICH
UNIVERSITE JOSEPH FOURIER - GRENOBLE 1 FRANCE
Physikalisch-Meteorologisches Observatorium Davos SCHWEIZ/SUISSE/SVIZZERA
Delivery of aerosol products for assimilation and environmental use
Resources of the Sea, Fisheries, Forecasting, Meteorology, Environmental Protection
Laboratoire d'Optique Atmosphèrique
Royal Netherlands Meteorological Institute
Belgian Institute for Space Aeronomy
Norwegian Institute for Air Research
Netherlands Organisation for Applied Scientific Research
Centre National de la Recherche Scientifique
Universidade de Evora
Commission of the European Communities
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE FRANCE
UNIVERSIDADE DE EVORA PORTUGAL
COMMISSION OF THE EUROPEAN COMMUNITIES ITALIA
Atmospheric aerosols affect human health, continental and marine ecosystems, visibility, and the Earth's climate, requiring dedicated monitoring of their properties. DAEDALUS is a focused project to make an inventory of existing data relevant to aerosol monitoring, assess the users' needs at the European level interims of troposphere and stratospheric aerosol properties, evaluate the scientific, technical, and institutional efforts needed to meet the users' needs, match the available aerosol data products with the information needed by the group of users, and improve methodologies for making optimal use of satellite data and for assimilating aerosol data in transport models. DAEDALUS will provide the necessary impetus for designing long-term sustainable and fully operational European monitoring of aerosol properties at regional and global scales over sea and over land, as foreseen in GMES.
Estimate of the aerosol properties over the ocean with POLDER
J.-L. Deuzé, M. HERMAN, A. MARCHAND, G. PERRY, Goloub PHILLIPPE, S. SUSANA, S. SUSANA et Didier TANRE
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The wide field of view imaging spectroradiometer Polarization and Directionality of the Earth's Reflectance (POLDER) developed by Centre National d'Etudes Spatiales and operated aboard the Japanese heliosynchronous platform Advanced Earth Observation Satellite (ADEOS) from October 30, 1996, to June 30, 1997, provided the first global systematic measurements of the spectral, directional, and polarized characteristics of the solar radiation reflected by the Earth/atmosphere system. These original observational capabilities offer an opportunity to enhance the characterization of several components of the global environment, especially the oceanic and terrestrial vegetal primary production, the aerosol physical and optical properties, and the tridimensional structure and microphysics of clouds. Here we examine the remote sensing of aerosols over the oceans. In a first step the aerosol optical thickness and Ångström exponent are derived from the radiance measurements. In a second step the polarization measurements are used for the retrieval of the aerosol refractive index. The inversion algorithm assumes spherical, nonabsorbing particles with monomodal lognormal size distribution. The adequacy of this modeling is discussed for a representative set of aerosol observations. Successful retrieval is generally achieved in the presence of small aerosols with Ångström exponent larger than ∼1.0. For such particles, polarization may provide information on the particle refractive index. As the Ångström exponent of the particle decreases, the data fitting residual errors increase, especially in polarized light, which prevents the retrieval of the aerosol refractive index. The trends of the discrepancies point out two shortcomings of the aerosol modeling. The theoretical results systematically underestimate the contribution of small polarizing particles in the polarization measurements for side-scattering angles ranging from 80° to 120°. This indicates very probably that aerosol models have to follow bimodal size distribution. On the other hand, the systematic trend of the directional behavior of the upward radiance and the lack of significant rainbow effect in the measurements result probably from nonsphericity of some large aerosols. Confirmation of these points requires improved analysis of the POLDER data.
Aerosols ; Space remote sensing ; Marine atmosphere ; Spectroradiometry ; Optical thickness ; Refraction index ; Algorithm ; Stokes parameter ; Polarization ;
Correction of the stratospheric aerosol radiative influence in the POLDER measurements
M. HERMAN, B. LAFRANCE et TAT SOON YEO
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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.
Stratosphere ; Stratospheric aerosol ; Atmospheric correction ; Radiative properties ; Polarimetry ; Satellite observation ; Performance ;
The Polar Ozone and Aerosol Measurement instrument
R. M. BEVILACQUA, Colette Brogniez, E Chassefière, D-T Chen, F. DALAUDIER, D. J. DEBRESTIAN, C. DENIEL, M.D. Fromm, W. GLACCUM, J. S. HORNSTEIN, R. KREMER, S. S. KRIGMAN, Jacqueline LENOBLE, R. L. LUCKE, J. D. Lumpe, J. J. OLIVERO, C. E. Randall, D W Rusch et E. P. SHETTLE
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The second Polar Ozone and Aerosol Measurement instrument (POAM II) is a spaceborne experiment designed to measure the vertical profiles of ozone, water vapor, nitrogen dioxide, aerosol extinction, and temperature in the polar stratosphere and upper troposphere with a vertical resolution of about 1 km. Measurements are made by the solar occultation technique. The instrument package, which has a mass of less than 25 kg, is carried on the Satellite Pour l'Observation de la Terre (SPOT) 3 spacecraft and has a design lifetime of 3-5 years. POAM II has provided data on the south polar ozone hole, north and south polar ozone phenomena, the spatial and temporal variability of stratospheric aerosols and polar stratospheric clouds, and has detected polar mesospheric clouds.
Photometer ; Design ; Data acquisition ; Data analysis ; Vertical profile ; Satellite observation ; Ozone ; Vapor ; Water ; Nitrogen dioxide ; Aerosols ; Atmospheric temperature ; Troposphere ; Stratosphere ; Polar region ; Spaceborne instruments ;
Remote sensing of cirrus radiative parameters during EUCREX'94. Case study of 17 April 1994. Part I : Observations
F. Albers, H. Chepfer, P. H. FLAMANT, Philippe Flamant, B. GERARD, J. PELON, L. SAUVAGE, L. Sauvage et V. TROUILLET
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During the intensive European Cloud and Radiation Experiment 1994 (EUCREX'94) conducted off the coast of Brittany (France) over the Atlantic Ocean during April 1994, natural cirrus have been analyzed from in situ and remote sensing measurements. The authors have particularly studied the case of 17 April 1994. For this day a cirrus bank is described by a complete dataset, that is, classic airborne thermodynamical measurements, microphysical (forward scattering spectrometer probe) and OAP-2D2-C (optical array probe-cloud) probes manufactured by Particle Measuring System, and radiative (Barnes Precision Radiation Thermometer, Eppley pyranometers, and upward- and downward-looking pyrgeometers) measurements above and below the cloud. More specific airborne instruments were used such as upward backscatter lidar with polarization capabilities (LEAN-DRE) on board the Avion de Recherches Atmosphériques et Télédétection and the Polarization and Directionality of the Earth's Reflectances (POLDER) radiometer on board the Falcon for measurement of bidirectional and polarized reflectances. The scene was also documented by NOAA-12/Advanced Very High Resolution Radiometer data. However, the nonsphericity of cirrus ice crystals is clearly demonstrated by the lidar backscattering depolarization ratio measurements (Δp = 24%) and by the absence of any rainbow in POLDER bidirectional reflectances. A specular reflection of the solar light observed on POLDER images indicates the presence of horizontally oriented ice particles in the cloud. All these optical properties will be studied in a companion paper (Part II) and compared with optical properties derived from microphysical models in order to evaluate the radiative impact of natural cirrus clouds.
Cirrus ; Observation data ; Radiative properties ; Optical properties ; Case study ; France ; East Atlantic ; Airborne instruments ; Spaceborne instruments ; Europe ;
Mineralogy of Saharan dust transported over northwestern tropical Atlantic Ocean in relation to source regions
Sandrine Caquineau, Annie Gaudichet, Annie Gaudichet, Laurent Gomes, Gilet L., Michel LEGRAND et M. Legrand
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 On the basis of daily Saharan dust samples collected at Sal Island (Cape Verde Archipelagos) and Barbados (Caribbean Sea) over 3 years, this study focuses on the mineralogical signature of the African sources providing dust over the tropical North Atlantic Ocean. First, the sources of the collected dust were localized by using relative clays abundance (illite-to-kaolinite ratio) combined with Meteosat infrared imagery, horizontal visibility, and backward trajectories of dusty air masses. Then, each identified source was linked to a single value of the illite-to-kaolinite ratio. Those results highlight that the clay content of the emitted dust depends directly on both the latitude and the longitude of the source. Dust originating from northwestern sources exhibits illite-to-kaolinite ratios higher than those from Sahelian regions. Likewise, illite-to-kolinite ratio decreases from west to east.
America ; Central America ; West Indies ; Atlantic Ocean Islands ; Atlantic Ocean ; Meteosat satellites ; Caribbean Sea ; Barbados ; Cape Verde Islands ; Tropical Atlantic Ocean ; Inorganic compound ; Image analysis ; Satellite observation ; Atmospheric dust ; Air mass ; Trajectory ; Infrared imaging ; Mineralogy ;