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Donald W. Beran

Abstract

Four types of chinook winds are described and features detectable in satellite pictures are shown. The hypothesis that large amplitude lee waves could be a possible driving mechanism for chinook winds is investigated for a case occurring in the Rocky Mountains during April 1963. It is shown that the stability of the surface inversion layer on the windward side of a mountain is related to the occurrence of chinook winds to the leeward side. This relationship leads to the speculation that chinook winds may undergo a quasi-diurnal fluctuation, in phase with the onset of the windward surface inversion.

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Robert L. Grossman and Donald W. Beran

Abstract

The occurrence of extreme low-level wind shear at 10 stations in the conterminous United States is investigated by applying a bivariate frequency-distribution analysis to rawinsonde and pibal data. Data for Denver, Colo., received additional analysis and showed that extreme wind shears were associated with particular synoptic conditions. Many stations indicated variation of extreme shear with season. Large values of extreme wind shear were found to correlate well with mean storm tracks in the conterminous United States.

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Harold W. Baynton, Jerold M. Bidwell, and Donald W. Beran

Abstract

Inversions at Point Arguello, California, as detected in 4½ years by rawinsondes at 0400 and 1600 PST, are related to surface wind direction and speed and surface temperatures. Nocturnal inversions based below 1000 ft msl have their maximum frequency in winter and their minimum in summer. Most of them occur with downslope surface winds. Afternoon inversions are most frequent in July and least frequent in January. Nocturnal surface inversions appear to develop when the downslope drainage air from the interior is cool enough to undercut the marine layer. There is evidence that the critical surface temperature for this to take place is 9C.

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Arnold H. Glaser, James C. Barnes, and Donald W. Beran

Abstract

A Monte Carlo technique simulates the effects of cloudcover on the performance of the Apollo On-board Navigation System. For each of three simulated Apollo missions, the probability of sighting at least a specific number of landmarks within the first two and one-half revolutions is determined. Cloudcover over the landmarks is derived from meteorological satellite data. These cloud amounts were found to be generally less than ground observed; the difference is believed to be due to the existence of small cumulus cells not resolved by the satellite, and the overestimation of sky cover by ground observers. A discussion of these factors is included.

The results of the mission simulation program indicate that the number of sightings can be materially increased by a choice of landmarks that are distributed to conform to the operational characteristics of the On-board Navigation System as much as by choice for optimum climate.

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