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  • Author or Editor: E. Raschke x
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E. Raschke
and
W. R. Bandeen

Abstract

The net flux of radiation at the top of the atmosphere and associated quantities (albedo and outgoing longwave radiation) were computed for five successive semimonthly periods from measurements of the radiance of emitted longwave radiation and reflected solar radiation obtained over the entire globe from the satellite Nimbus II during the period 16 May–28 July 1966. The anisotropy of the reflection characteristics of the earth-atmosphere system was considered for the first time with gross empirical models derived from airplane and balloon observations.

The global planetary albedo was found to be between 29 and 31%, while the mean planetary temperature ranged between 254 and 255K. Both results deviate from the corresponding values of earlier investigations in such a way as to suggest that in those investigations the cloudiness or its effect on radiative tranfer, especially in the tropics and subtropics, was overestimated. The global averages of the radiation balance indicate a slight deficit of about 0.005 cal cm−2 min−1, when computed with a value of the solar constant of 2.00 cal cm−2 min−1. Seasonal trends and day-to-day variations of the earth's radiation field are also discussed.

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O. Danne
,
M. Quante
,
D. Milferstädt
,
H. Lemke
, and
E. Raschke

Abstract

In this study, data obtained from measurements with a ground-based vertical-pointing 95-GHz polarimetric cloud radar are analyzed. The investigations concentrate on the relationships between the Doppler spectral moments observed in different regions of nonprecipitating cirrostratus and altostratus decks connected with warm fronts approaching the radar site. In some of these cases, a remarkably well-defined relationship between the radar reflectivity and the spectral width is found. It is demonstrated how this relationship can be used to obtain information on the size distributions and the fallspeeds of the particles in the investigated cloud sections. It is found that if single parameters of the size distributions, for example, are parameterized by a lognormal distribution, they cannot be determined with an acceptable accuracy. However, at least the changes of these parameters, such as mean particle diameter and particle concentration, with changing reflectivity as well as the behavior of the corresponding particle fallspeeds, can be described with the help of empirical relations between the Doppler moments. A main result is that significant changes in reflectivity within a cloud section (e.g., of 10 dBZ e ) must correspond with a change in the relation between particle size and fallspeed, most commonly described by empirical power laws, and, therefore, probably with changes in particle shapes. This kind of radar data analysis will help to come to a better understanding of the microphysical and dynamical properties of the investigated cloud types, especially if further information from simultaneous measurements with other remote sensors is available.

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