Abstract
The 94-GHz airborne HIAPER Cloud Radar (HCR) has been deployed in three major field campaigns, sampling clouds over the Pacific between California and Hawaii (2015), over the cold waters of the Southern Ocean (2018), and characterizing tropical convection in the Western Caribbean and Pacific waters off Panama and Costa Rica (2019). An extensive set of quality assurance and quality control procedures were developed and applied to all collected data. Engineering measurements yielded calibration characteristics for the antenna, reflector, and radome, which were applied during flight, to produce the radar moments in real-time. Temperature changes in the instrument during flight affect the receiver gains, leading to some bias. Post project, we estimate the temperature-induced gain errors and apply gain corrections to improve the quality of the data. The reflectivity calibration is monitored by comparing sea surface cross-section measurements against theoretically calculated model values. These comparisons indicate that the HCR is calibrated to within 1–2 dB of the theory. A radar echo classification algorithm was developed to identify “cloud echo” and distinguish it from artifacts. Model reanalysis data and digital terrain elevation data were interpolated to the time-range grid of the radar data, to provide an environmental reference.
Highlights
The 94-GHz airborne High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) Cloud Radar (HCR) has been deployed in three major field campaigns, sampling clouds over the Pacific between California and Hawaii (2015), over the cold waters of the Southern Ocean (2018), and characterizing tropical convection in the Western Caribbean and Pacific waters off Panama and Costa Rica (2019)
We identify the surface by searching for the highest reflectivity value in specific range gates, which are calculated from the altitude of the radar and the topography data
Other sea surface calibration (SScal) events were removed because data measured on one side of the aircraft were distinctly different from data measured on the other side of the aircraft (Figure 13d)
Summary
The High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) aircraft, which is operated by the National Center for Atmospheric Research (NCAR) for the National Science Foundation (NSF), is a state-of-the-art observational platform available to the scientific community. Ber of pre-determined flight patterns laid out in a grid format either over the Pacific Ocean or the Caribbean Sea. The aircraft generally flew at very high altitudes of over 14 km, at the extreme end of (and in rare cases exceeding) the maximum range of the HCR (Figure 2c). The radar fields, except for the primary power fields DBMVC and DBMHX, are censored (i.e., set to a missing value) when there is not sufficient signal to yield useful information This censoring is done using thresholds applied to the SNR and NCP fields, on a gate-by-gate basis. The variability of the influence of gravity over the globe means that the sea surface height does not accurately follow the WGS84, with deviations of over 70 m in some places To correct for these deviations, the measured GPS altitude is corrected using the Earth Gravitation Model This metadata is added to the data stream and is used extensively in the calibration correction procedures carried out in the data quality phase during post-processing
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