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S. TWOMEY

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.

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S. Twomey

Abstract

When non-absorbing scatterers (e.g., cloud drops) are added in an absorbing layer (e.g., a dust layer), the optical paths of the radiation will be greatly changed if the scattering component is optically thick. The absorption will thus be altered. Results are given of numerical computations to determine the effect of non-absorbing cloud drops on the absorption of radiation by a dust layer. Absorption is found to be decreased for low angles of incidence and increased for higher angles of incidence.

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S. Twomey

Abstract

No abstract available.

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S. Twomey

Abstract

No abstract available.

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S. Twomey

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.

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S. Twomey

Abstract

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S. Twomey

Abstract

The application of nonlinear iterafive algorithms to two-dimensional tomographic reconstructions is discttszed and a number of numerical examples are given, using as an illustrative basis reconstruction of the spatial distribution of liquid water in clouds from measurements of microwave attenuation. (The method, however, is not restricted to that specific problem and appears to be especially suitable for inversions involving a large number of unknowns.)

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S. Twomey

Abstract

No abstract available.

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S. Twomey

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.

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S. Twomey

Abstract

The size of cloud nuclei acting at 0.75% supersaturation was estimated by using varying flow rates through Nuclepore filters to discriminate between different sizes. The nuclei, sampled in clean continental and maritime air at Robertson, N.S.W., were found to be small, not much greater than the theoretical minimum radius of ∼1−6 cm permitted by nucleation theory.

This result agrees quite well with previous estimates of cloud-nucleus size from experiments carried out at Chesapeake Bay, Md. It is concluded that the atmospheric residence time of cloud nuclei cannot be more than a few days and that they must be composed entirely or partly of a water-soluble material since an insoluble particle of such a small size could not nucleate condensation at supersaturations of the order of 1% or less.

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