HIAPER Cloud Radar (HCR)

The HIAPER cloud radar (HCR) is an airborne, polarimetric, millimeter-wavelength radar that serves the atmospheric science community by providing cloud remote sensing capabilities to the NSF/NCAR HIAPER Gulfstream V aircraft.

Example of HCR reflectivity and radial velocity.

HCR provides unique observations of the formation and evolution of clouds. Its high sensitivity allows for the precise detection of liquid and ice clouds, aiding our understanding of the effects of clouds on the regional and global weather and climate. Derived scientific products, such as melting layer altitude, convective and stratiform echo type, or hydrometeror particle identification, provide additional information on the observed cloud and precipitation processes.


HCR on the GV aircraft.


HCR is mounted in the aircraft's underwing pod. A lens antenna illuminates a rotatable reflector, which allows for 240° cross-track scanning as well as staring, for example, at zenith or nadir. In staring mode, the beam is stabilized every 20 ms for changes in roll and pitch angles caused by platform motion. Measurements such as reflectivity, velocity, and dual-polarization variables are computed with a resolution of ∼20 m in range and a temporal resolution of 10 Hz.

Parameter Specification
Antenna 0.3 m, lens
Antenna gain 45.7 dBi
Beamwidth 0.73 deg
Transmit frequency 94.4 GHz
Transmit wavelength 3.2 mm
Transmitter Klystron
Peak transmit power 1.6 kW
Pulse width 0.2 - 1.0 μs
Pulse repetition frequency (PRF) up to 10 kHz
Range resolution 20-180 m
Unambiguous range 15 km, PRF=10kHz
Receiver bandwidth 20 MHz
Receiver noise figure 8.9 dB
Sensitivity -37.0 dBZ at SNR=-10dB, 1 km, and 256 ns pulse
Typical reflectivity uncertainty 1-2 dB
Unambiguous velocity +/- 7.75 m/sec, PRF=10kHz
Typical radial velocity uncertainty 0.2 m/s at W=2 m/s
Typical dwell time 100 ms

NCAR/EOL HCR Team. (2014). HIAPER Cloud Radar (HCR). UCAR/NCAR - Earth Observing Laboratory. https://doi.org/10.5065/D6BP00TP.