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Michael D. King, Harshvardhan, and Albert Arking

distribution. In addition to models of the radiative properties of the aerosol layer, a simple modelof the latitudinal distribution of aerosol optical thickness as a function of time is developed, based ondiffusive transport in latitude and exponential decay in time. These parametenzations for solar and infraredradiation, together with the dispersion model, permit climate models to account for the evolution of anaerosol size distribution from post-volcanic conditions to background conditions.1

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John A. Augustine, Christopher R. Cornwall, Gary B. Hodges, Charles N. Long, Carlos I. Medina, and John J. DeLuisi

radiation and may have a cooling effect because they reflect some of the incoming solar radiation back to space. It is well documented that the earth's climate temporarily cooled following the major volcanic eruptions of the last century ( Dutton and Christy 1992 ; Hansen et al. 1992 ). Aerosols may also have an indirect effect on climate by changing the radiative properties of clouds ( Charlson et al. 1992 ). Owing to the contrasting effects that aerosols can have on climate, Hansen et al. (2000

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Grant W. Petty

on rain-cloud properties. The accuracy of any forward model, in turn, depends critically on all three of the following factors: realism in the specification of hydrometeor sizes, shapes, and phases encountered in real rain clouds and their three-dimensional distribution; the accurate specification of local optical properties (e.g., phase function, single scatter albedo, and volume extinction coefficient) from knowledge of the above hydrometeor properties; and the accuracy and generality of the

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J. Fischer and H. Grassl

optical thickness, surface albedo, and solar zenith angles. All these; properties haveto be successfully incorporated into a cloud-top heightalgorithm. For the development and. definition of acloud-top pressure (height) algorithm we have chosenradiative transfer modeling because of the advantageof systematically varying cloud properties and errorestimates. A comparison of calculated and measuredradiances as well as a test of the developed algorithmsis given in an accompanying paper (part 2

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T. Ackerman and M. B. Baker

areas may contain high concentrations of anthropogenic aerosol particles. Thepossible role of these particles in perturbing the optical and dynamical properties of the clouds is an importantquestion for climate studies. The direct radiative effects of unactivated aerosol particles in stable stratusclouds have been calculated at X=0.5 ~m. Several simplifying assumptions have been made relating thebehavior of such particles in the high humidity environment within the cloud to thdr physicochemicalmake

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Zhien Wang, Kenneth Sassen, David N. Whiteman, and Belay B. Demoz

too optically thick for lidar to penetrate, supercooled altocumulus clouds can often be penetrated by lidar to measure cloud-layer physical and optical depths and cloud optical properties ( Young et al. 2000 ). Although they have small LWP, altocumulus clouds emit significant signals in the IR window region, which AERI can generally detect. The general principles and basic retrieval steps to use AERI for cloud studies are discussed by Smith et al. (1993) , and a combination of AERI with lidar or

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Jun Li, Hung-Lung Huang, Chian-Yi Liu, Ping Yang, Timothy J. Schmit, Heli Wei, Elisabeth Weisz, Li Guan, and W. Paul Menzel

, aerosols, or other factors associated with global change. Cloud parameters, such as cloud-top pressure (CTP), effective cloud emissivity or effective cloud amount (ECA), cloud particle size (CPS) in diameter, cloud optical thickness (COT) at 0.55- μ m wavelength, ice water path (IWP), and liquid water path (LWP), are important to weather and climate prediction ( Diak et al. 1998 ; Bayler et al. 2000 ; Kim and Benjamin 2000 ; Stephens et al. 1990 ). The capability to make cloud microphysical property

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A. J. Alkezweeny

theproperties and formation of aerosol particles. It was found that the average of several distributions obtainedduring extended periods of time can be approximated by AN/AD oc D-4 for the optical size range. Furthermore, aerosol particles in the plume are growing by coagulation and chemical conversion. The conversionrate of SO2 to sulfate is aboul~ 11% h-~ and the sulfate is composed of mixture of a acid and neutralized saltaerosol.1. In~oducfion One part of the Battelle-Pacific Northwest Laboratories

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Carl C. Norton, Frederick R. Mosher, Barry Hinton, David W. Martin, David Santek, and William Kuhlow

received 10 December 1979, in final form 1 March 1980)ABSTRACT A technique has been developed to infer the optical thickness of Saharan dust from SynchronousMeteorological Satellite (SMS) brightness measurements at visible wavelengths. The scattering modelconsists of an air layer, a dust layer and a lower boundary of variable albedo. Single-scatter properties ofthe dust computed from Mie theory were the basis for calculations by plane-parallel theory of radiativetransfer in the dust layer. Radiative

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Zhien Wang and Kenneth Sassen

microphysical properties, other approaches are also tested ( Matrosov 1999 ). To retrieve cloud microphysical properties correctly in terms of the effect of clouds on the radiation budget, it is vital to include optical (i.e., visible and infrared spectral regions) measurements in the algorithm. Although β and downwelling IR radiance are used in some algorithms ( Intrieri et al. 1993 ; Matrosov et al. 1992 ), the extinction coefficient σ, derived from the same lidar measurement, was not used. There are

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