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  • Author or Editor: W. L. Ecklund x
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Wayne M. Angevine
and
W. L. Ecklund

Abstract

With the use of simultaneous correction for radial wind, the accuracy of radio acoustic sounding systems for the measurement of temperature has been substantially improved. The temperature accuracy can now be affected by a number of factors that have been considered negligible in previous work. This paper describes two types of errors, those due to atmospheric effects and those due to approximations in the temperature retrieval equation. The errors are examined in a set of convective boundary layer RASS and radiosonde data. In the category of atmospheric effects, two errors are computed. The first is caused by a range error due to the gradient of signal strength. This range error is newly proposed and is approximately 0.05°−0.1°C. The second is an error due to wind and turbulence of about 0.1°C. Commonly used approximations for factors in the retrieval equation contribute errors of a few tenths of a degree Celsius. A significant difference remains after these two corrections have been applied to the sample data.

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W. L. Ecklund
,
D. A. Carter
, and
B. B. Balsley

Abstract

In this paper we describe a boundary layer radar recently developed at NOAA's Aeronomy Laboratory. This radar extends wind profiler technology by using a small, relatively inexpensive radar to provide continuous, high-resolution wind measurements in the first few kilometers of the atmosphere. Although the radar was developed for use in a “hybrid” mode with existing 50 MHz profilers in the tropical Pacific, the system can equally well be a stand-alone device to study boundary layer problems.

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B. B. Balsley
,
A. C. Riddle
,
W. L. Ecklund
, and
D. A. Carter

Abstract

We present the analysis of three months of continuous sea-surface current data obtained by a VHF wind profiling radar at Christmas Island in the central equatorial Pacific. These results, which were obtained during the construction phase of the profiler when the antenna had not yet been phased to eliminate sea scatter, show a number of interesting features of the coastal flow, as well as the flow at greater distances from the island. We report here both the average surface current characteristics as well as features of the shorter-term variability. In addition, we discuss the idea that such sea-surface current measurements could be obtained quite easily in the central Pacific, provided that they were made in conjunction with existing and/or proposed profiler sites.

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Wayne M. Angevine
,
W. L. Ecklund
,
D. A. Carter
,
K. S. Gage
, and
K. P. Moran

Abstract

Improved radio acoustic sounding system (RASS) technology for use with radar wind profilers has been developed and applied to 915-MHz and 50-MHz profilers. The most important advance is the simultaneous measurement of the wind velocity to correct the acoustic velocity measurement for air motion. This eliminates the primary source of error in previous RASS measurements, especially on short time scales. Another improvement is the use of an acoustic source that is controlled by the same computer that controls the radar. The source can be programmed to produce either a swept frequency or a random hopped frequency signal. Optimum choices of the acoustic source parameters are explored for particular applications. Simultaneous measurement of acoustic and wind velocity enables the calculation of heat flux by eddy correlation. Preliminary heat flux measurements are presented and discussed. Results of the use of RASS with oblique beams are also reported.

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K. S. Gage
,
W. L. Ecklund
,
A. C. Riddle
, and
B. B. Balsley

Abstract

The magnitude of backscattered power observed at vertical incidence by a VHF radar is related to atmospheric stability in accordance with the Fresnel scattering model. Utilizing a modified Fresnel scattering model, we can determine tropopause height objectively from the observed vertical profile of backscattered power. The method is tested with observations of the Alpine Experiment (ALPEX; France), Platteville, Colorado and Poker Mat, Alaska radars taken since 1979. Using 750 m resolution the tropopause is found to be within a few hundred meters of the tropopause determined from nearly simultaneous radiosonde observations and using 2.2 km resolution the tropopause is found to be within about 600 m. Furthermore, radar-determined tropopause heights can be automatically scaled from existing records, or even routinely determined on-line.

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K. S. Gage
,
J. R. Mcafee
,
W. L. Ecklund
,
D. A. Carter
,
C. R. Williams
,
P. E. Johnston
, and
A. C. Riddle

Abstract

After a decade of development, VHF wind profilers are being used for atmospheric research at several locations in the tropical Pacific. A prototype 50-MHz wind profiler was installed on Christmas Island in 1985 and has operated continuously since March 1986 to monitor tropical wind fields in the altitude range 1.8–1 8 km. This paper presents an overview of the Christmas Island wind profiler and reviews its performance. A survey of sample wind observations and a brief climatology of the observed winds are included.

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