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H. B. Howell

Abstract

Results of multiple-scattering calculations of diffuse reflection and diffuse transmission from scattering layers of different particle size and/or index of refraction are presented. Comparison of the results for each scattering model indicates the extent to which earlier calculations (for one cloud model) are generally applicable.

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H. Jacobowitz and H. B. Howell

Abstract

No abstract available.

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H. B. Howell and H. Jacobowitz

Abstract

A matrix method for multiple-scattering problems, which was the subject of earlier papers, is extended to include the state of polarization in the description of both singly and multiply scattered raditaion. Comparisons of numerical results from the extended matrix method with published values obtained by two other methods are presented (for the special cue of a Rayleigh scattering layer of optical depth τ = 0.25). The values of total intensity (Stokes parameter I) calculated by the matrix method show excellent agreement with published values, while the values of the Stokes parameters Q) and U show slight systematic deviations. For the particular case studied, the numerical results indicate that the inclusion of polarization affects the values of I by less than 10%, and in many cases by less than 17%.

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S. TWOMEY and H. B. HOWELL

Abstract

Instability limits the usefulness of indirect sounding, i.e. the deduction of a physical distribution from a set of observations which represent an integral transform of the former. A method is presented which allows a stable, but smoothed, solution to be obtained in certain cases. As an illustration of the application of the method, the deduction of vertical ozone distribution from measurements of the spectral distribution of scattered ultraviolet radiation is discussed. Graphs showing results from several possible methods of inversion are included to show the difficulties associated with such indirect measurements.

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S. Twomey, H. Jacobowitz, and H. B. Howell

Abstract

If the radiation field is approximated by a discrete distribution at points or latitude circles on the unit sphere, matrix relationships can be written between incident and reflected or transmitted radiation fields. The reflection and transmission matrices thus defined are shown to satisfy algebraic equations which can be used to compute the properties of thick layers by building up the thick layers from thinner sublayers, the starting point being a layer so thin that it is effectively a single scattering layer only.

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S. Twomey, H. Jacobowitz, and H. B. Howell

Abstract

Results of calculations of diffuse reflection and transmission of cloud-model layers are presented. These calculations which are based on matrix methods developed by the authors and discussed in a previous paper include the effects of cloud thickness, absorption, drop-size distribution, liquid water content, and directions of the incident and emergent radiation.

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W. L. Smith and H. B. Howell

Abstract

In this paper, the algorithm used for calculating the water vapor distribution from SIRS-B spectral radiances is given. Examples are presented illustrating the effects of errors in the water vapor absorption coefficients and the specified temperature profile on the retrieval of the water vapor profile. Comparisons of satellite-derived and radiosonde-observed water vapor profiles indicate that the errors of the SIRS-derived relative humidity in the middle troposphere (i.e., the 400–600 mb layer) are less than 20%. Relative humidity errors in the lower troposphere (600–1000 mb) are somewhat larger but still less than 30%.

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W. L. Smith, H. B. Howell, and H. M. Woolf

Abstract

It is shown that the partial interferogram measurement technique, originally developed to separate the trace gas emissions from a spectral signal dominated by background radiation (from the earth's surface) and emissions from major constituents (H2O and CO2), has application to the vertical sounding problem. The interferometric technique will enable relatively high vertical temperature profile resolution to be achieved and will provide absolute accuracies of temperature approaching, and at same levels exceeding, 1°C.

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J. E. Dinger, H. B. Howell, and T. A. Wojciechowski

Abstract

Measurements of the concentration of cloud nuclei, which are activated at a supersaturation of 0.75%, were made aboard an aircraft at various altitudes in a subsident air mass over the North Atlantic Ocean and on the cast coast of Barbados, West Indies. The measurements were made on air samples at normal temperatures as well as on air samples heated to various temperatures up to 600C. In this way the volatility of the cloud nuclei was compared to the volatility as measured in a similar manner in the laboratory on nuclei artificially generated and of a known composition.

The measurements at Barbados showed that ∼50% of the cloud nuclei were nonvolatile at the temperatures used and thus were similar to artificially generated nuclei composed of sea salt; the remaining nuclei were destroyed by temperatures ≳320C. The aircraft measurements showed the fraction of volatile cloud nuclei to increase with altitude with all nuclei being volatile above the inversion layer.

These measurements indicate that in a subsident marine atmosphere only a fraction of the cloud nuclei at the sea surface are composed of sea salt, this fraction decreasing with altitude such that the sea salt nuclei are confined to the lower few kilometers. Based on the work of other investigators it is suggested that the volatile cloud nuclei are sulfates or sulfuric acid particles which result from the oxidation in the atmosphere of S02 or H2S.

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S. Twomey, H. B. Howell, and T. A. Wojciechowski

Abstract

No abstract available.

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