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R. B. Chadwick, K. P. Moran, R. G. Strauch, G. E. Morrison, and W. C. Campbell

A new radar technique for measuring winds in the lower atmosphere is discussed. It is an extension of the well-known FM-CW technique and has the same advantages of relatively low cost and high flexibility for a clear-air radar. Two different types of wind data from clear-air returns are presented. The first is horizontal wind data by the FM-CW radar; these are compared with winds obtained from a tethered balloon. The second is radial velocities associated with convection cells drifting past the radar. Also, two types of data processing are illustrated. The first is off-line processing of recorded digital data, and the second is real-time processing using a commercial spectrum analyzer.

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Earl E. Gossard, Russell B. Chadwick, Thomas R. Detman, and John Gaynor

Abstract

Radars and acoustic sounding systems sense properties of the turbulence structure of the atmosphere. If atmospheric turbulence can be related to the mean gradient parameters, Doppler radars and acoustic sounders can provide information about height profiles of quantities such as temperature and refractive index as well as wind in stable regions of the atmosphere. In this paper turbulent and mean quantities were measured on the 300 m meteorological tower at the Boulder Atmospheric Observatory near Erie, Colorado, and the relationships between the turbulent and mean gradient quantities were examined in order to evaluate hypotheses for simplifying the kinetic energy balance and refractive index variance equations. FM-CW radar measurements of backscattered power and Doppler spectral width were also made for comparison with tower-measured refractive index spectra and Doppler velocity spectra. Height distributions of the turbulent dissipation rate within stable layers are shown and viscous cutoff radar wavelengths calculated.

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E. E. Gossard, R. B. Chadwick, W. D. Neff, and K. P. Moran

Abstract

The use of ground-based clear-air Doppler radars to observe the structure of elevated atmospheric layers and associated flux quantities is described. Case studies in which radar and balloon data were available are analyzed. Doppler second-moment (velocity variance) data are used to calculate turbulent kinetic energy dissipation rate ε. Velocity variance, refractive index structure parameter and wind shear are used to estimate the refractive index gradient across elevated weather-frontal interfaces. A case is analyzed in which both acoustic-sounder and radar-sounder data are available, so profiles of structure parameter of both temperature and humidity can be deduced and used to calculate the fluxes of heat and moisture within the frontal interface. The fluxes deduced from radar data are compared with corresponding in situ measurements made by aircraft in other geographical regions. The relationship between the turbulent Prandtl number and the Richardson number emerges as very important to the generalization of the technique to the whole stable atmosphere.

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J. C. Kaimal, N. L. Abshire, R. B. Chadwick, M. T. Decker, W. H. Hooke, R. A. Kropfli, W. D. Neff, F. Pasqualucci, and P. H. Hildebrand

Abstract

Three in-situ and five remote sensing techniques for measuring the height of the daytime convective boundary layer were compared. There was, as a rule, good agreement between the different systems when the capping inversion was steep and well defined, and some variability when the stratification was not so sharply defined. Two indirect methods for estimating boundary-layer heights from the length scales of convective motions in the layer are also discussed.

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B. L. Weber, D. B. Wuertz, R. G. Strauch, D. A. Merritt, K. P. Moran, D. C. Law, D. van de Kamp, R. B. Chadwick, M. H. Ackley, M. F. Barth, N. L. Abshire, P. A. Miller, and T. W. Schlatter

Abstract

The first wind profiler for a demonstration network of wind profilers recently passed the milestone of 300 h of continuous operation. The horizontal wind component measurements taken during that period are compared with the WPL Platteville wind profiler and the NWS Denver rawinsonde. The differences between the network and WPL wind profilers have standard deviations of 2.30 m s−1 and 2.16 m s−1 for the u- and v-components, respectively. However, the WPL wind profiler ignores vertical velocity, whereas the network radar measures it and removes its effects from the u- and v-component measurements. The differences between the network wind profiler and the NWS rawinsonde (separated spatially by about 50 km) have standard deviations of 3.65 m s−1 and 3.06 m s−1 for the u- and v-components, respectively. These results are similar to those found in earlier comparison studies. Finally, the new network wind profiler demonstrates excellent sensitivity, consistently reporting measurements at all heights msl from 2 to nearly 18 km with very few outages.

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