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  • Author or Editor: W. H. Jasperson x
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W. H. Jasperson

Abstract

The results of a program to study the time and space variability of the wind field below 5 km are presented. Wind data were collected using pilot balloons tracked with the METRAC positioning system. Balloons were launched at 10-30 min intervals from a single launch point and at 30 min intervals from pairs of launch points separated by 20 m, 4.415 km and 20.910 km. Winds were averaged over 100 m layers. Experiments were separated by cyclonic and anticyclonic weather patterns. It was found that the average time variability of the wind for anticyclonic weather patterns followed a 1/3 power law for time lags from 30 to 300 min. The result of frontal passages during the cyclonic experiments increased the power law relationship to about 1/2. The wind variability for a space separation of 4.415 km was found to correspond to a time lag of ∼ 17 min. The wind variability for a space separation of 20.910 km was found to correspond to a time lag of ∼90 min though this estimate is based upon relatively few observations. It was found that variabilities as small as 1 m s−1 could be accurately measured with the balloon and ground system used in this study.

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W. H. Jasperson

Abstract

An experiment has been performed to estimate the limiting accuracy of free atmosphere wind measurements over 100 m layers using 100 g pilot balloons. Errors in the wind measurement due to the tracking system used in this study are found to be only a few centimeters per second. Upper bound estimates of the total rms error in the wind measurement are found to be less than 0.5 m s−1 for wind speed and 0.7 m s−1 for the magnitude of the vector wind velocity.

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K. S. Gage
and
W. H. Jasperson

Abstract

The results of an analysis of the variability of the atmospheric wind field below 5 km is presented for a limited sample of high-resolution wind profiles. The wind was measured by tracking balloons utilizing the Control Data METRAC positioning system installed at St. Cloud, Minnesota. Balloons were launched sequentially 30 min apart for a period of 7 h during the afternoon of 31 March 1976. The wind, averaged over 100 m intervals, was analyzed for temporal variability for lags τ up to 240 min. Temporal variability of the wind at individual altitudes on this day did not support any unique power law. However, when the variability statistics at all levels were combined the averaged variability was consistent with the τ power law.

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K. S. Gage
,
W. P. Birkemeier
, and
W. H. Jasperson

Abstract

The results of a high-altitude probing experiment are presented which demonstrate the capability of measuring atmospheric stability at tropopause altitudes using a 940-MHz forward-scatter CW radar system. Vertical profiles of the potential temperature gradient measured by radiosondes launched under the common volume of the radar system are well correlated with profiles of received power from radar data, taken nearly simultaneously. Thus, the tropopause can be located within a few hundred meters and its stability structure can be observed as it evolves.

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W. H. Jasperson
,
G. D. Nastrom
, and
D. C. Fritts

Abstract

Wind and temperature data collected on commercial airliners are used to investigate the effects of underlying terrain on mesoscale variability. These results expand upon those of Nastrom et al., by including all available data from the Global Atmospheric Sampling Program (GASP) and by more closely focusing on the coupling of variance with the roughness of the underlying terrain over mountainous regions. The earlier results, showing that variances are larger over mountains than over oceans or plains, with greatest increases at wavelengths below about 80 km, are confirmed. Statistical tests are used to confirm that these differences are highly significant. Over mountainous regions the roughness of the underlying terrain was parameterized from topographic data and it was found that variances are highly correlated with roughness and, in the troposphere, with background wind speed. Average variances over the roughest terrain areas range up to about ten times larger than those over the oceans. These results are found to follow the scaling with stability predicted in the framework of linear gravity wave theory. The implications of these results for vertical transports of momentum and energy, assuming they are due to gravity waves and considering the effects of intermittency and anisotropy, are also discussed.

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W. P. Birkemeier
,
A. B. Fontaine
,
K. S. Gage
,
S. A. Gronemeyer
,
W. H. Jasperson
, and
F. S. Sechrist

Abstract

The ability of a forward-scatter CW radar to measure cross-path wind speed profiles is demonstrated from the results of a two-week observation period in June 1971. Radar-measured winds are compared with wind speeds measured simultaneously by radiosondes and pibals. It is concluded that forward-scatter CW radar is a sensitive atmospheric probe which can accurately measure atmospheric winds.

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