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Timothy L. Wilfong, Elias M. Lau, Bob L. Weber, David A. Merritt, and Scott A. McLaughlin

Abstract

Radar wind profiler (RWP) systems observe radar returns from refractive index fluctuations due to clear-air turbulence. The Doppler spectra used to compute the moments of the returned signal always include noise from various sources and may contain multiple signals. A critical first step in detecting signals is the objective determination of the noise level in each spectrum. Several spectra may be averaged to improve signal detection. In addition to or instead of a mean, a median may be applied to successive spectra in order to reject transient interference. Monte Carlo simulations were used to examine the effects of the median versus the mean on the objective noise determination. When a median is used, it was found the noise statistics calculations must be slightly modified.

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Elías Lau, Scott McLaughlin, Frank Pratte, Bob Weber, David Merritt, Maikel Wise, Gary Zimmerman, Matthew James, and Megan Sloan

Abstract

The DeTect Inc. RAPTOR velocity–azimuth display boundary layer (VAD-BL) radar wind profiler is a pulsed Doppler radar used to make automatic unattended measurements of wind profiles in the lower atmosphere. All data products are produced on site, in real time, and utilize quality control software to screen out interference. The nominal frequencies are 915 and 1290 MHz but other frequencies can be accommodated. While the architecture is similar to other boundary layer wind profilers, the RAPTOR VAD-BL is designed to provide consistently superior data quality due to its antenna design and signal processing capabilities. The antenna is a high-performance parabolic reflector with a feed that is designed in house for the operational frequency of the radar. The antenna is mounted on a robust military-grade azimuth-only positioner. The RAPTOR VAD-BL can collect data from several opposing beam positions with the goal of producing higher-quality wind data using the velocity–azimuth display (VAD) algorithm. The Advanced Signal Processing Engine (ASPEN) software used to calculate winds outperforms conventional consensus algorithms. The health and status of all critical subsystems is monitored via the profiler health monitor (PHM), a stand-alone monitor with its own microprocessor. Results from systems deployed for operational applications show the potential for the retrieval of high-quality data with excellent height coverage and a solid design that allows the antenna to perform under sustained high wind loading.

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Jorge L. Salazar-Cerreño, V. Chandrasekar, Jorge M. Trabal, Paul Siquera, Rafael Medina, Eric Knapp, and David J. McLaughlin

Abstract

A novel analytical method is presented for evaluating the electrical performance of a radome for a dual-polarized phased-array antenna under rain conditions. Attenuation, reflections, and induced cross polarization are evaluated for different rainfall conditions and radome types. The authors present a model for estimating the drop size distribution on a radome surface based on skin surface material, area, inclination, and rainfall rate. Then, a multilayer radome model based on the transmission-line-equivalent circuit model is used to characterize the radome’s scattering parameters. Numerical results are compared with radar data obtained in the Next Generation Weather Radar (NEXRAD) and Collaborative Adaptive Sensing of the Atmosphere (CASA) systems, and good agreement is found.

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David McLaughlin, David Pepyne, V. Chandrasekar, Brenda Philips, James Kurose, Michael Zink, Kelvin Droegemeier, Sandra Cruz-Pol, Francesc Junyent, Jerald Brotzge, David Westbrook, Nitin Bharadwaj, Yanting Wang, Eric Lyons, Kurt Hondl, Yuxiang Liu, Eric Knapp, Ming Xue, Anthony Hopf, Kevin Kloesel, Alfred DeFonzo, Pavlos Kollias, Keith Brewster, Robert Contreras, Brenda Dolan, Theodore Djaferis, Edin Insanic, Stephen Frasier, and Frederick Carr

Dense networks of short-range radars capable of mapping storms and detecting atmospheric hazards are described. Composed of small X-band (9.4 GHz) radars spaced tens of kilometers apart, these networks defeat the Earth curvature blockage that limits today s long-range weather radars and enables observing capabilities fundamentally beyond the operational state-of-the-art radars. These capabilities include multiple Doppler observations for mapping horizontal wind vectors, subkilometer spatial resolution, and rapid-update (tens of seconds) observations extending from the boundary layer up to the tops of storms. The small physical size and low-power design of these radars permits the consideration of commercial electronic manufacturing approaches and radar installation on rooftops, communications towers, and other infrastructure elements, leading to cost-effective network deployments. The networks can be architected in such a way that the sampling strategy dynamically responds to changing weather to simultaneously accommodate the data needs of multiple types of end users. Such networks have the potential to supplement, or replace, the physically large long-range civil infrastructure radars in use today.

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