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- Author or Editor: S. Twomey x
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Abstract
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Abstract
The difficulties and instabilities accompanying the inversion of radiance data to infer temperature structure are closely related to the high degree of interdependence existing among these nominally independent measurements.
The radiance measurements discussed in the accompanying papers are shown to be interdependent to a marked degree. It is shown that one of the measurements can be predicted from the others with an accuracy which is only a little worse than the experimental accuracy.
The application of this kind of analysis to determine optimum choices of measurements and the information content thereof is outlined.
Abstract
The difficulties and instabilities accompanying the inversion of radiance data to infer temperature structure are closely related to the high degree of interdependence existing among these nominally independent measurements.
The radiance measurements discussed in the accompanying papers are shown to be interdependent to a marked degree. It is shown that one of the measurements can be predicted from the others with an accuracy which is only a little worse than the experimental accuracy.
The application of this kind of analysis to determine optimum choices of measurements and the information content thereof is outlined.
Abstract
Atmospheric transmission functions, being negative-exponential in character, are strongly interdependent and thereby limit the information content of indirect sensing even if a large number of measurements is made.
Abstract
Atmospheric transmission functions, being negative-exponential in character, are strongly interdependent and thereby limit the information content of indirect sensing even if a large number of measurements is made.
Abstract
By increasing droplet concentration and thereby the optical thickness of a cloud, pollution acts to increase the reflectance (albedo) of clouds; by increasing the absorption coefficient it acts to decrease the reflectance. Calculations suggest that the former effect (brightening of the clouds in reflection, hence climatically a cooling effect) dominates for thin to moderately thick clouds, whereas for sufficiently thick clouds the latter effect (climatically a warming effect) can become dominant.
Abstract
By increasing droplet concentration and thereby the optical thickness of a cloud, pollution acts to increase the reflectance (albedo) of clouds; by increasing the absorption coefficient it acts to decrease the reflectance. Calculations suggest that the former effect (brightening of the clouds in reflection, hence climatically a cooling effect) dominates for thin to moderately thick clouds, whereas for sufficiently thick clouds the latter effect (climatically a warming effect) can become dominant.
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Using published data for water vapor absorption and for absorption by liquid (or ice) water, the absorption of solar radiation by clouds was computed for several representative cloud models. Absorption was found to approach 20% of the solar flux for the more absorbing and thicker clouds. There were systematic differences between continental and maritime clouds, the latter absorbing more for the same cloud thickness—an effect produced by the greater absorption efficiency of the larger maritime drops.
Abstract
Using published data for water vapor absorption and for absorption by liquid (or ice) water, the absorption of solar radiation by clouds was computed for several representative cloud models. Absorption was found to approach 20% of the solar flux for the more absorbing and thicker clouds. There were systematic differences between continental and maritime clouds, the latter absorbing more for the same cloud thickness—an effect produced by the greater absorption efficiency of the larger maritime drops.
Abstract
Using Nuclepore filters at a sequence of flow rates, to discriminate according to particle size, and a suitable mathematical inversion procedure, particle size distributions have been obtained for surface atmospheric aerosol samples. Measurements in relatively unpolluted air at Robertson, N.S.W., Australia, yield a fairly reproducible size distribution, with a maximum always close to 10−6 cm radius; measurements in more polluted air at The University of Arizona have led to very similar size distributions.
Abstract
Using Nuclepore filters at a sequence of flow rates, to discriminate according to particle size, and a suitable mathematical inversion procedure, particle size distributions have been obtained for surface atmospheric aerosol samples. Measurements in relatively unpolluted air at Robertson, N.S.W., Australia, yield a fairly reproducible size distribution, with a maximum always close to 10−6 cm radius; measurements in more polluted air at The University of Arizona have led to very similar size distributions.
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Abstract
Maritime air was followed from the coast, and measurements of seal-salt nucleus distributions were carried out. It was found that the concentrations encountered in air which had been over land for a considerable time ranged from very low values to values approaching those usually found in maritime air. It also seemed that convective cloud formation or precipitation rapidly lowered the salt concentration. In the absence of such factors, no appreciable diminution in total concentration occurred; vertical mixing, however, often gave rise to elevated salt concentrations at higher levels. Very low concentrations were found above post-frontal subsidence inversions over land, in air streams which had recently come from over the ocean.
Abstract
Maritime air was followed from the coast, and measurements of seal-salt nucleus distributions were carried out. It was found that the concentrations encountered in air which had been over land for a considerable time ranged from very low values to values approaching those usually found in maritime air. It also seemed that convective cloud formation or precipitation rapidly lowered the salt concentration. In the absence of such factors, no appreciable diminution in total concentration occurred; vertical mixing, however, often gave rise to elevated salt concentrations at higher levels. Very low concentrations were found above post-frontal subsidence inversions over land, in air streams which had recently come from over the ocean.
