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  • Author or Editor: W. L. Ecklund x
  • Journal of Applied Meteorology and Climatology x
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R. R. Rogers
,
D. Baumgardner
,
S. A. Ethier
,
D. A. Carter
, and
W. L. Ecklund

Abstract

Wind profilers are radars that operate in the VHF and UHF hands and are designed for detecting the weak echoes reflected by the optically clear atmosphere. An unexpected application of wind profilers has been the revival of an old method of estimating drop size distributions in rain from the Doppler spectrum of the received signal. Originally attempted with radars operating at microwave frequency, the method showed early promise but was seriously limited in application because of the crucial sensitivity of the estimated drop sizes to the vertical air velocity, a quantity generally unknown and, at that time, unmeasurable. Profilers have solved this problem through their ability to measure, under appropriate conditions, both air motions and drop motions. This paper compares the drop sizes measured by a UHF profiler at two altitudes in a shower with those measured simultaneously by an instrumented airplane. The agreement is satisfactory, lending support to this new application of wind profilers.

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Wayne M. Angevine
,
S. K. Avery
,
W. L. Ecklund
, and
D. A. Carter

Abstract

A 915-MHz boundary-layer wind profiler radar with radio acoustic sounding system (RASS) capability has been used to measure the turbulent fluxes of heat and momentum in the convective boundary layer by eddy correlation. The diurnal variation of the heat flux at several heights between 160 and 500 m above ground level and values of the momentum flux for 2-h periods in midday from 160 to 1000 m are presented, as well as wind and temperature data. The momentum flux is calculated both from the clear-air velocities and from the RASS velocities, and the two results are compared.

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W. L. Ecklund
,
K. S. Gage
,
G. D. Nastrom
, and
B. B. Balsley

Abstract

Multiheight time series of atmospheric vertical velocities in the troposphere and lower stratosphere observed by clear-air Doppler radar are presented at various locations around the world. Frequency spectra of vertical velocities determined from these data sets are compared with the objective of developing a preliminary climatology. We emphasize the nearly universal shape and magnitude of spectra observed during low-wind conditions. These spectra are quite flat for frequencies between the buoyancy and inertial frequencies, and they closely resemble the internal wave spectra observed in the ocean. Spectra observed under strong wind conditions, on the other hand, are greatly enhanced in magnitude, approaching the f −5/3 spectral slope observed for the spectrum of horizontal motions. Finally, spectra determined from both quiet and active periods at Poker Flat, Alaska, possess spectral slopes and amplitudes intermediate to those spectra determined solely from quiet or active periods at other locations.

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