Aircraft
Tropical cyclones are ideal subjects for study from instrumented
aircraft.
The vortex core is relatively small--only a few hundred kilometers
across. An airplane can traverse it 5-10 times in the course of
a flight lasting 6-8 hours. The great rotational inertia of the
swirling wind means that the balanced vortex changes slowly during
the time that an airplane can remain on station. Expendable probes
can report atmospheric or oceanic conditions as they drop from
flight level. The size of the core is comparable with the range
of 5 or 10 cm wavelength search radars. Although aircraft radars
are relatively low powered and have small antennas, the ability
to move through the storm enables them to observe storms in detail.
The foregoing advantages compound for aircraft equipped
with Doppler radars, particularly so if they can fly coordinated
patterns in pairs to produce true dual-Doppler winds. NOAA's aircraft
operations center flies two WP-3D turboprop that represent a unique
scientific resource and are the mainstay of HRD's annual campaign
of airborne hurricane observations. Starting in 1997, a third
aircraft, a Gulfstream IVSP jet entered the inventory. This airplane
is dedicated to synoptic surveillance to obtain observations in
the environment around hurricanes to improve operational track
forecasts.
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