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Y. Fouquart, B. Bonnel, M. Chaoui Roquai, R. Santer, and A. Cerf

28 $OURNAL OF CLIMATE AND APPLIED METEOROLOGY VOLUM-26Observations of Saharan Aerosols: Results of ECLATS. Field Experiment. Part h Optical Thicknesses and Aerosol Size Distributions Y. FOUQUART, B. BOhr~EL, M. CHAOUI ROQUA~ AND R. SANTERUniversitd des Sciences et Techniques de Lille, Laboratoire d'Optique Atmosphg, rique, France A. CERF*Universitd d;4bidjan, Laboratoire

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A. Ben Mohamed and J-P. Frangi

DECEMBER 1986 A. BEN MOHAMED AND J.-P. FRANGI 1807Results from Ground-based Monitoring of Spectral Aerosol Optical Thickness andHorizontal Extinction: Some Specific Characteristics of Dusty Sahelian Atmospheres A. BEN MOHAMED AND J.-P~ FRANGI Universit~ de Niamey, Facult~ des Sciences, D~partement de Physique, Niamey, Niger (Manuscript received 14 December 1985, in final form 26

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Yoram J. Kaufman and Robert S. Fraser

1983, in final form 13 June 1983) ABSTRACY In order to utilize satellite measurements of optical thickness over land for estimating aerosol propertiesduring air pollution episodes, the optical thickness was measured from the surface and investi~ted. Aerosoloptical thicknesses have been derived from solar transmission measurements in eight spectral bands withinthe band X440-870 nm during the summers of 1980 and 1981 near Washington, DC. The optical thicknessesfor the eight

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Takahiro Yabe, Robert Höller, Susumu Tohno, and Mikio Kasahara

) estimation of the aerosol radiative forcing at the surface, the top of the atmosphere, and in the atmosphere; 4) discussion of the columnar aerosol optical properties and the range of surface radiative forcing on the basis of the derived relationship between the aerosol optical thickness and the surface radiative forcing, together with comparison with radiative transfer calculations using model aerosols, and 5) comparison of the results of this study with observations of aerosol radiative forcing at

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J. L. Deuze, C. Devaux, M. Herman, R. Santer, and D. Tanre

- ~BSTRACT In July 1983, the summer transpo~ of $aharian aerosols across the Mediterranean Sea was observed. Thedust cloud was particularly dense and was clearly detected in A.V.H.R.R. and METEOSAT imageries. Optical~hlckne~ses and Angstr6m coet~cients have been derived from these pictures. Durin$ the same ~riod, groundbased observations--transmission, aureole and polarization measurements--were ~ormed at the Obr, e~valoiredc Haute Provence (southeast of France). Measumt aerosol optical thicknesses at

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C. A. Faizoun, A. Podaire, and G. Dedieu

exponent, which is an estimate of the aerosolparticle size, is derived from the spectral dependence of the optical thickness. Although the sites were locatedfar from Sahara Desert aerosol sources, the observed aerosol optical thicknesses were high, with a mean annualvalue of 0.5 at 550 rim. The spectral dependence of aerosol optical thickness is generally low, with a meanannual value of ~ngstrrm's exponent of 0.4. The aerosol optical thickness and the atmospheric water vaporcontent are both

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Maria João Costa, Ana Maria Silva, and Vincenzo Levizzani

Introduction The growing consciousness of the strong influence of atmospheric aerosol on atmospheric processes (e.g., Houghton et al. 2001 ), and consequently on climate, prompts local and global studies aimed at quantifying the aerosol load in the atmosphere (aerosol optical thickness: AOT), as well as aerosol optical properties. Aerosol particles play a twofold role in the atmosphere: on one hand they directly scatter and absorb solar radiation, and on the other they enter cloud

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J. D. Spinhirne, J. A. Reagan, and B. M. Herman

-sectionprofiles could be evaluated. Measurements were made with an elastic backscatter ruby iidar system withcalibration by a standard target procedure. The results from 20 measurement cases are presented. Forlayer-aerosol optical thicknesses ~ 0.04, useful results were obtained, and corroboration by solarrudiometer aerosol optical depth data was found. The mean mixed-layer aerosol extinction-to-backscatterratio for the measurements was 19.5 sr with a standard deviation of $.3 sr. With the use of an aerosol

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Michael D. King, Harshvardhan, and Albert Arking

observations, on the reflection, transmission and absorption of radiationby the stratosphere as a function of latitude, optical thickness and aerosol size distribution. Results arepresented and parameterized for each of two wavelength intervals in the shortwave region and 17 wavelengthintervals in the longwave region for three models of the aerosol size distribution. They include one modelrepresenting the unperturbed stratospheric aerosol plus two models based on measurements of the El Chichonaerosol size

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Owen B. Toon and James B. Pollack

and optical thickness of stratosphericand tropospheric aerosols is proposed. The uncertainties involved in making the model are emphasized, andsome of the model's implications are discussed. The model is designed for, and biased toward, global averageradiative transfer calculations.1. Introduction Every study of the effects of aerosols on the Earth'sradiation balance requires a d'etailed model of the properties of aerosols. Since the properties of aerosols arenot well known each radiative

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