Abstract
Abstract. NCAR EOL is investigating potential configurations for the next-generation airborne phased array radar (APAR) that is capable of retrieving dynamic and microphysical characteristics of clouds and precipitation. The APAR will operate at C band. The APAR will use the electronic scanning (e-scan) feature to acquire the optimal number of independent samples for recording research-quality measurements. Since the airborne radar has only a limited time for collecting measurements over a specified region (moving aircraft platform ∼ 100 m s−1), beam multiplexing will significantly enhance its ability to collect high-resolution, research-quality measurements. Beam multiplexing reduces errors in radar measurements while providing rapid updates of scan volumes. Beamwidth depends on the size of the antenna aperture. Beamwidth and directivity of elliptical, circular, and rectangular antenna apertures are compared and radar sensitivity is evaluated for various polarimetric configurations and transmit–receive (T/R) elements. In the case of polarimetric measurements, alternate transmit with alternate receive (single-channel receiver) and simultaneous reception (dual-channel receiver) is compared. From an overall architecture perspective, element-level digitization of T/R module versus digital sub-array is considered with regard to flexibility in adaptive beamforming, polarimetric performance, calibration, and data quality. Methodologies for calibration of the radar and removing bias in polarimetric measurements are outlined. The above-mentioned engineering options are evaluated for realizing an optimal APAR system suitable for measuring the high temporal and spatial resolutions of Doppler and polarimetric measurements of precipitation and clouds.
Highlights
Characterizing location, intensity, and motion of hurricanes, tornados, and extreme precipitation events and understanding effects of clouds and aerosols on the earth radiation budget requires a better understanding of the kinematic and microphysical processes within these storms
Scanning Doppler radar with dual-polarization capability on an airborne platform is capable of measuring dual-Doppler winds and retrieving particle types and shapes and liquid–ice water contents using reflectivity (Z), differential reflectivity (ZDR), specific propagation phase (KDP), and linear depolarization ratio (LDR)
A staggered pulse repetition frequency (PRF) technique for extending Doppler Nyquist interval was extremely valuable for the ELDORA is considered, but its evaluation is beyond the scope of this document
Summary
Characterizing location, intensity, and motion of hurricanes, tornados, and extreme precipitation events and understanding effects of clouds and aerosols on the earth radiation budget requires a better understanding of the kinematic (storm motion and structure) and microphysical processes (particle growth, phase changes) within these storms This remains a challenge for both the scientific and operational communities. No other instrument other than an airborne polarimetric Doppler phased array radar (APAR) system has the potential to estimate high temporal and spatial measurements of 3-D winds and microphysics concurrently (Vivekanandan et al, 2014). CETP became LATMOS (Laboratoire Atmospheres, Milieux, Observations Spatiales) It collects research-quality Doppler and reflectivity measurements that continue to set the standard for airborne radar; ELDORA X-band radar’s penetration into precipitation is limited by attenuation and it is not designed to collect polarimetric measurements to remotely estimate microphysics.
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