On the measurement of wind speeds in tornadoes with a portable CW/FM-CW Doppler radar

Conference · Tue Jan 01 04:00:00 EST 1991

OSTI ID:6096554

Bluestein, H B ^[1]; Unruh, W P ^[2]

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1. Oklahoma Univ., Norman, OK (USA). School of Meteorology
2. Los Alamos National Lab., NM (USA)

Both the formation mechanism and structure of tornadoes are not yet well understood. The Doppler radar is probably the best remote-sensing instrument at present for determining the wind field in tornadoes. Although much has been learned about the non-supercell tornado from relatively close range using Doppler radars at fixed sites, close-range measurements in supercell tornadoes are relatively few. Doppler radar can increase significantly the number of high-resolution, sub-cloud base measurements of both the tornado vortex and its parent vortex in supercells, with simultaneous visual documentation. The design details and operation of the CW/FM-CW Doppler radar developed at the Los Alamos National Laboratory and used by storm-intercept teams at the Univ. of Oklahoma are described elsewhere. The radar transmits 1 W at 3 cm, and can be switched back and forth between CW and FM-CW modes. In the FM-CW mode the sweep repetition frequency is 15.575 kHz and the sweep width 1.9 MHz; the corresponding maximum unambiguous range and velocity, and range resolution are 5 km, {plus minus} 115 m s{sup {minus}1}, and 78 m respectively. The bistatic antennas, which have half-power beamwidths of 5{degree}, are easily pointed wit the aid of a boresighted VCR. FM-CW Data are recorded on the VCR, while voice documentation is recorded on the audio tape; video is recorded on another VCR. The radar and antennas are easily mounted on a tripod, and can be set up by three people in a minute or two. The purpose of this paper is to describe the signal processing techniques used to determine the Doppler spectrum in the FM-CW mode and a method of its interpretation in real time, and to present data gathered in a tornadic storm in 1990. 15 refs., 7 figs.

• Research Organization: Los Alamos National Lab., NM (USA)
• Sponsoring Organization: DOE; NSF; USDOE, Washington, DC (USA); National Science Foundation, Washington, DC (USA)
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 6096554
• Report Number(s): LA-UR-91-556; CONF-9104193--1; ON: DE91008589; CNN: ATM-8902594
• Country of Publication: United States
• Language: English

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440800 -- Miscellaneous Instrumentation-- (1990-)
47 OTHER INSTRUMENTATION
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99 GENERAL AND MISCELLANEOUS
DATA ANALYSIS
DATA PROCESSING
DESIGN
DISASTERS
DOPPLER EFFECT
DYNAMIC LOADS
FEDERAL REGION VI
FREQUENCY DEPENDENCE
FUNCTIONS
MAGNETIC STORAGE DEVICES
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METEOROLOGY
MONITORING
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OPERATION
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RADAR
RANGE FINDERS
REAL TIME SYSTEMS
RECORDING SYSTEMS
REMOTE SENSING
SAFETY
SPECTRAL DENSITY
SPECTRAL FUNCTIONS
STORMS
TEXAS
TORNADOES
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VELOCITY
VIDEO TAPES
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