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Y. J. Kaufman, D. Tanré, B. N. Holben, S. Mattoo, L. A. Remer, T. F. Eck, J. Vaughan, and Bernadette Chatenet

used for remote sensing of the presence of aerosol, for example, the effective aerosol optical thickness derived from Advanced Very High Resolution Radiometer (AVHRR) ( Husar et al. 1997 ) and the absorbing aerosol index derived from Total Ozone Mapping Spectrometer (TOMS) ( J. R. Herman et al. 1997 ). New efforts with present satellites [AVHRR; Ocean Color and Temperature Scanner (OCTS); Polarization and Directionality of the Earth's Reflectances (POLDER)] and new satellite missions [Earth

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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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F. Waquet, J. Riedi, L. C. Labonnote, P. Goloub, B. Cairns, J-L. Deuzé, and D. Tanré

respectively of multispectral measurements (0.41–14.2 μ m) and spectral (0.44–0.865 μ m) multidirectional and polarized passive measurements to derive aerosol and cloud parameters on a global scale. The main aerosol parameters currently estimated from these measurements are the aerosol optical thickness (AOT) over both ocean ( Tanré et al. 1997 ; Herman et al. 2005 ) and land ( Kaufman et al. 1997 ; Deuzé et al. 2001 ; Hsu et al. 2004 ) and the particle size over ocean. For clouds, the current passive

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Teruyuki Nakajima, Tadahiro Hayasaka, Akiko Higurashi, Gen Hashida, Naser Moharram-Nejad, Yahya Najafi, and Hamzeh Valavi

University, Sendai, JapanNASER MOHARRAM-NEJAD, YAHYA NAJAFI, AND HAMZEH VALAVIDepartment of the Environment of lran, Tehran, lran(Manuscript received 16 August 1994, in final form 15 January 1995)ABSTRACT Solar radiation measurements were made using sun photometers and pyranometers during 3l May-7 June1991 at several places in Iran and during 12 June-17 September 1991 at a fixed place, Bushehr, Iran. In thefirst period the aerosol optical thickness had values about 0.4 at the wavelength of 0.5 pm in

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Philip Stier, Johann Feichter, Silvia Kloster, Elisabetta Vignati, and Julian Wilson

state. Therefore, a nonlinear response of the aerosol optical thickness to emission changes is to be expected and is not further investigated. The annual zonal-mean distribution of the aerosol optical depth ( τ ) and the percent changes for the different scenarios are depicted in Fig. 5 . The strongest effect of anthropogenic emissions on τ can be attributed to the sulfuric emission from fossil fuels, industry, and biofuels. In the NAS scenario, zonal-mean optical depths between 20° and 70°N

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Guido Visconti, Marco Verdecchia, and Giovanni Pitari

the work by McCormick and Swissler(1983) and it allows us to translate the initial backscattering ratios to mass mixing ratios for the aerosols.These ratios can be converted, in turn, to optical thicknesses using the conversion value for integrated backscatter to aerosol optical thickness as determined inthe work by Swissler et al. (i983). The value derivedwas 42.8 + 7.4 sr (steradian) for X = 0.6943 txm. Figure 3 shows the behavior of the total mass in thetwo-year integration of the model

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Glenn E. Shaw

of ~r = :t:0.002 (r is the optical thickness)at the Mauna Loa Observatory, Hawaii. Suspended aerosols above the observatory attenuated light byan average of 1.9% (in the vertical direction) at a wavelength of 5000 .~, and the average attenuationvaried with wavelength as X-x.s. Air masses from northerly directions were most turbid, e=0.021~0.015,while those from southwesterly direction were least turbid, ~ =0.017-4-0.005. The lowest values of opticalextinction varied as k-'.a while those from

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Jacek Chowdhary, Brian Cairns, and Larry D. Travis

average NO x burden by half ( Dentener and Crutzen 1993 ). Reliable evaluation of both of these effects and of aerosol transport models used to provide present and future aerosol climatologies, requires precise global measurements of the aerosol optical thickness, chemical composition, size distribution, and number density. Thus far, the only operational aerosol satellite product available has been the optical thickness retrieved over the ocean using channel-1 radiances from the Advanced Very High

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Philip B. Russell and John M. Livingston

layer belowa tower-mounted radiometer pair are derived. This radiometer pair is used to measure the change in surfaceplus layer albedo caused by the aerosol layer. The consistency of albedo and optical thickness measurementsis tested by comparing measured albedo changes to those calculated from the optical thickness measurements.When reasonable values are assumed for particle refractive index and relative size distribution (not measuredin this experiment), results agree to within the uncertainty

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Tomoaki Nishizawa, Shoji Asano, Akihiro Uchiyama, and Akihiro Yamazaki

, several authors (e.g., Jayaraman et al. 1998 ; Meywerk and Ramanathan 1999 ; Conant 2000 ; Rajeev and Ramanathan 2001 ) made estimates of the aerosol forcing efficiency ( β ) as well as the aerosol radiative forcing in the Indian Ocean region. The forcing efficiency β is defined as the change in radiative forcing per unit change in aerosol visible optical thickness, say, at a wavelength of 500 nm ( τ 500 ). It is a useful parameter for more directly assessing the aerosol direct radiative effect

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