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  • Author or Editor: Peter S. Ray x
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Peter S. Ray

Abstract

Tornadic storms passed between the two NSSL Doppler radars on 20 April and 8 June, 1974. Both radars simultaneously collected Dopplar data throughout these storms. From the derived velocity fields, vorticity and divergence calculations were made. Strongest convergence is noted in the weak echo region and between opposing vorticity centers.

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Peter S. Ray
and
Conrad Ziegler

Abstract

A technique to remove the ambiguity in Doppler mean velocity estimates is described. The technique assumes that along a radial, or portion of a radial, the velocity estimates are quasi-uniformly distributed about the mean. If the data do not meet this criterion, the velocities are adjusted such that they are distributed about the mean.

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Peter S. Ray
and
Karen L. Sangren

Abstract

Observing programs utilizing Doppler radar must have them deployed in optimum locations to best satisfy experimental objectives and maximize economies. One wishes to determine the coordinate triples (xi , yi , zi ), where i equals the number of radars, which maximize the value of the data to be collected. The optimum location is governed by a value or objective function. Here, possible networks of two to nine radars are given for two different error specifications. The objective functions with both error distributions maximize the quantity (AREAL COVERAGE/ERROR). The procedure is to search the finite number of local maxima for the global maximum in the value of the objective function. This is done by employing a searching algorithm at each of a number of starting vectors which are close enough to the local maxima to converge to the desired local maxima. In all cases, the network obtained by considering all radars simultaneously is superior to that obtained by combining optimum smaller sub-networks. Our results suggest the expected benefits for networks with additional constraints, reflecting the more complex experimental objectives particular to some individual field program. For example, the number of radars needed and their optimal configuration can be determined for a field program requiring a specified areal coverage (probability that a desired event will occur) and resolution (to retrieve a specified scale of motion).

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Brenda C. Johnson
,
Judith Stokes
, and
Peter S. Ray

Abstract

Optimum design of a Doppler radar system for operation in a severe storm environment will depend on the maximum unambiguous velocity. Radial velocities of severe storms are examined from four Doppler radars over several hours on 20 May 1977. The probability of a radial velocity occurrence for a given pulse repetition frequency-wavelength combination is presented.

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Peter S. Ray
,
David P. Jorgensen
, and
Sue-Lee Wang

Abstract

Airborne Doppler radar can collect data on target storms that are quite widely dispersed. However, the relatively long time required to sample an individual storm in detail, particularly with a single aircraft, and the amplification of the statistical uncertainty in the radial velocity estimates when Cartesian wind components are derived, suggests that errors in wind fields derived from airborne Doppler radar measurements would exceed those from a ground based radar network which was better located to observe the same storm. Error distributions for two analysis methods (termed Overdetermined and Direct methods) are given and discussed for various flight configurations. Both methods are applied to data collected on a sea breeze induced storm that occurred in western Florida on 28 July 1982. Application of the direct solution, which does not use the continuity equation, and the overdetermined dual-Doppler method, which requires the use of the continuity equation, resulted in similar fields. Since the magnitude of all errors are unknown and the response of each method to errors is different, it is difficult to assess overall which analysis performs better; indeed each might be expected to perform best in different parts of the analysis domain. A flexible collection strategy can be followed with different analysis methods to optimize the quality of resulting synthesized wind fields.

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Brenda C. Johnson
,
Judith Stokes
, and
Peter S. Ray

Abstract

Optimum design of a Doppler radar system for operation in a severe storm environment will depend on the maximum unambiguous velocity. Radial velocities of severe storms are examined from four Doppler radars over several hours on 20 May 1977. The probability of a radial velocity occurrence for a given pulse repetition frequency-wavelength combination is presented.

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Peter S. Ray
,
J. J. Stephens
, and
K. W. Johnson

Abstract

An objective procedure for determining optimum radar positions in a multiple-Doppler radar network is given for the objective criteria of maximizing the integrated reliability. It is demonstrated for arrays of three to seven radars, including cases where some positions are fixed. The optimum locations for a three-Doppler radar network are at the vertices of an equilateral triangle. Subject to the chosen objective function the best deployment does not result from simply adding additional radars one-by-one to an existing radar network.

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Donald W. Burgess
,
Larry D. Hennington
,
Richard J. Doviak
, and
Peter S. Ray

Abstract

A single-Doppler data display has been developed which allows simultaneous presentation of the principal moments of the Doppler spectrum while retaining ease of viewing and interpretation. Display severe storm signatures are described and an example of data collected in a tornadic storm is presented. A tornado signature is identified, its evolution is followed, and comparisons between the signature and the tornado damage track are made.

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Peter S. Ray
,
R. J. Doviak
,
G. B. Walker
,
D. Sirmans
,
J. Carter
, and
B. Bumgarner

Abstract

On 20 April 1974 a tornadic storm passed between the two NSSL Doppler radars spaced about 42 km apart. Both radars simultaneously collected Doppler data throughout the storm. Air motions synthesized from these data provide the first three-dimensional display of Doppler-derived wind fields in a tornadic storm. Cyclonic circulation, associated with the tornado, and regions of intense up- and down-drafts are clearly evident.

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Richard J. Doviak
,
Peter S. Ray
,
Richard G. Strauch
, and
L. Jay Miller

Abstract

Variance in horizontal and vertical winds are predicted when these components are computed from dual-Doppler velocity measurements combined with terminal velocity estimates and the continuity equation. Errors in horizontal wind magnitude and direction are shown to be functions of wind direction and speed as well as spatial location. Vertical wind could be estimated with errors less than a few meters per second up to altitudes near 14 km over a region 4d × 4d, where 2d is the radar separation. Vertical wind variance at high altitudes is related to accumulation of errors due to the integration of the continuity equation. The cause of wind variance is assumed to be uncertainty in mean Doppler velocity estimates produced by spectrum broadening mechanisms (e.g., shear, turbulence). Two interpolation methods, used to estimate Doppler velocity at common grid locations, are compared and their contribution to Doppler velocity variance reduction is calculated. Terminal velocity variance has been related to uncertainties in drop-size distributions and reflectivity estimate variance. The methods derived herein are applied to determine the errors in wind speeds calculated from dual-Doppler data.

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