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Jehuda Neumann and Ariel Cohen


The effect of the introduction of one or two layers of particulate matter on the heating by direct solar radiation of the earth surface-atmosphere system is calculated for a cloudless sky. It is found for a fairly wide range of absorption and backscatter coefficients of the particles with respect solar radiation that when we have but one particle layer, either near the surface or in the lower stratosphere, the combined system is cooled; the atmosphere is heated (for a finite absorption) but this heating is offset by the greater cooling of the surface. Thus, our conclusions are different in some respects from those advanced by Charlson and Pilat and, to a lesser extent, from those inferred by McCormick and Ludwig.

If we have two layers of particles, one near the surface and the other in the lower stratosphere, and if we assume that both layers have the same optical characteristics with regard to solar radiation, then the earth surface-atmosphere system may actually gain heat provided that the absorption coefficient of the particle layers is fairly large with respect to the backscatter coefficient.

We estimate from the equations of the model that the layer of particles injected into the lower stratosphere by the 1963 Mt. Agung eruption absorbed and backscattered a total of about 6% of the solar radiation reaching the lower stratosphere.

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Ariel Cohen, Jehuda Neumann, and William Low


The previously adopted values of the depolarization factor of clear atmospheric air are checked with the values obtained by lidar facilities, and with those obtained in laboratory measurements, using scattering of a He-Ne gas laser. These values and the importance of the depolarization factor in lidar measurements are discussed.

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