Data
from Expendable Probes Expendable
instruments are routinely launched from the National
Oceanic and Atmospheric Administration (NOAA), Aircraft
Operations Center’s (AOC) WP-3D
Lockheed Orions and the Gulfstream
IV-SP aircraft in various environments, from benign
weather to the strongest hurricane eye walls, to gather
vertical profiles of the atmosphere or upper regions
of the ocean.
In
recent years, the primary expendable probe has been
the GPS
dropwindsonde, a meteorological instrument that
descends from the aircraft to the sea surface, transmitting
information back to the aircraft while in the air. The
GPS
dropwindsondes measure air temperature, dewpoint,
atmospheric pressure, and use the GPS positioning to
detect horizontal and vertical winds. These data are
measured and transmitted twice per second while the
probe is in the air. NOAA’s Gulfstream
IV-SP primary mission during hurricane season is
to fly in the environment surrounding a hurricane, launching
GPS
dropwindsondes at predetermined locations in data
sparse regions to gather vital information regarding
the steering currents that will determine a hurricane's
future track and likely landfall position.
AVAPS
Installation in 19 inch rack |
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Dropsonde
Sensor
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The
WP-3D Lockheed Orions
aircraft not only augment these Gulfstream
IV-SP surveillance missions, but also deliver
GPS
dropwindsondes into the most extremely dynamic
wind, turbulence and precipitation areas of tropical
cyclones. Recent findings regarding the strength
and location of low altitude wind maxima, gained
from GPS
dropwindsondes, are helping redefine rules of
thumb forecasters rely upon for hurricane wind warnings. |
Other
aircraft-launched expendable probes include
Aircraft Expendable BathyThermographs (AXBTs),
Aircraft Expendable Current Probes (AXCPs)
and Airborne Expendable Conductivity Temperature
Depth (AXCTD) probes. The AXBTs transmit sea
surface temperature versus depth as the thermistor
sinks through the water column. AXBTs provide
key information about ocean temperature (an
important factor in determining the possible
strength a hurricane may reach). AXCPs measure
horizontal ocean current velocity with depth,
an important tool for understanding heat transport
and ocean/atmosphere dynamics. The AXCTDs
measure the ocean salinity, or saltiness (proportional
to conductivity), and temperature, which are
necessary 1) for computing ocean density,
stability and buoyancy, and 2) for identifying
different ocean water masses. |
GPS
DropSonde |
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More information about the GPS dropwindsonde can be found at the University Corporation for Atmospheric Research web site.
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