IERSD/NOA owns unique equipment for the in situ measurement
and remote sensing of rainfall. This equipment includes
a mobile weather radar, a 2-D video disdrometer and a network
of rain gauges with data loggers.
The X-POL weather radar system is an X-band (3.2 cm wavelength)
dual polarization Doppler radar unit mounted on the flatbed
of a truck. The radar was manufactured by Binet Inc. in
cooperation with NCAR, USA. The range of the system is selectable
up 150km, with resolution down to 30m and a maximum angle
rotation of the antenna at 25 deg/sec. The simultaneous
horizontal and vertical polarization transmission allows
fast antenna scanning without compromising the quality of
polarimetric measurements. Radar direct measured quantities
include horizontal and vertical polarization reflectivity,
Doppler velocity, spectral width, and differential phase
shift. The system can give estimations in high resolution
of the distribution of precipitation distinguishing between
liquid and solid state of water as well as the wind field.
These characteristics make it ideal for hydrometeorological
studies, agricultural applications and air traffic control.
In the past years X-POL has been successfully used in collaboration
with University of Connecticut in field programs in USA,
including the NASA-CAMEX Keys Area Microphysics Project
(KAMP) and the NSF funded International H2O Project (IHOP)
in Western Oklahoma.
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NOA's 2-D video disdrometer is also one of a small number
of such instruments worldwide. The disdrometer was manufactured
by the Johanneum Research Institute for Applied Systems Technology,
Austria.
It uses two light beams in orthogonal arrangement and fast
line-scan cameras to record the shape of particles falling
through the light beams. The system has a resolution of 0.2mm
and estimates the fall velocity, the horizontal velocity,
the diameter, the oblateness and the canting angle of each
particle, the dropsize distribution and the rain rate with
an accuracy of better than 10%. The disdrometer and the rain
gauges provide reference measurements of rain characteristics
for calibration and validation of the measurements of the
X-POL radar.
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