Introduction - Severe Convective Storms and Tornadoes: Observations and Dynamics - page 19

Figure 1.12. Illustration of pseudo dual-Doppler analysis technique as wind vectors are
resolved at fixed points in space from intersecting oblique beams, but at slightly different
times. In this example, the fore and aft beams of pulse trains in the fore and aft directions
at an angle from the flight track are noted at points A and B. The spacing between the N and
N þ 1, etc. pulse trains is given by the product of the speed of the aircraft with the time between
the transmission of the pulse trains (adapted from McCaul et al., 1987).
Studies) using a NOAA P-3 aircraft and radar system that had been used for a
number of years in hurricanes. Early on, two aircraft, each with its own radar,
were used and each aircraft flew nearly perpendicular flight legs; later, a scanning
technique similar to the one used with NASA Doppler lidar was implemented and
called FAST (fore-aft scanning technique).
The first ground-based, portable, X-band Doppler radar was built at LANL
and converted for meteorological use by Wes Unruh and colleagues at LANL.
First used by the author in 1987, a number of tornadoes were probed at close
range between 1987 and 1995 and maximum wind speeds were estimated from
Doppler velocity spectra. A high-frequency (W-band, 95MHz), very narrow beam
(0.6 ), truck-mounted, scanning, mobile Doppler radar was built at the University
of Massachusetts at Amherst by a group headed by Bob McIntosh; the group
included Andy Pazmany, who led the field effort. Having undergone a number of
upgrades (the antenna was replaced in 1999 with a dish having a half-power beam-
width of only 0.18 ), the fine-resolution radar has been used since 1993; however,
high-quality data in tornadoes were not collected until 1999, for the very first time,
during a tornado outbreak in central Oklahoma on May 3.
During the first year of VORTEX (Verification of the Origins of Rotation in
Tornadoes Experiment) in 1994, airborne Doppler radar measurements by the
NOAA P-3 system near Newcastle, Texas were collected for the first time in which
the entire life history of a tornado was documented. During the second year of
VORTEX in 1995, a number of excellent data sets documenting the life histories