The Atmospheric Imaging Radar: Simultaneous Volumetric Observations Using a Phased Array Weather Radar

Abstract

Mobile weather radars often utilize rapid-scan strategies when collecting observations of severe weather. Various techniques have been used to improve volume update times, including the use of agile and multibeam radars. Imaging radars, similar in some respects to phased arrays, steer the radar beam in software, thus requiring no physical motion. In contrast to phased arrays, imaging radars gather data for an entire volume simultaneously within the field of view (FOV) of the radar, which is defined by a broad transmit beam. As a result, imaging radars provide update rates significantly exceeding those of existing mobile radars, including phased arrays. The Advanced Radar Research Center (ARRC) at the University of Oklahoma (OU) is engaged in the design, construction, and testing of a mobile imaging weather radar system called the atmospheric imaging radar (AIR). Initial tests performed with the AIR demonstrate the benefits and versatility of utilizing beamforming techniques to achieve high spatial and temporal resolution. Specifically, point target analysis was performed using several digital beamforming techniques. Adaptive algorithms allow for improved resolution and clutter rejection when compared to traditional techniques. Additional experiments were conducted during two severe weather events in Oklahoma. Several digital beamforming methods were tested and analyzed, producing unique, simultaneous multibeam measurements using the AIR.

Observations of a Cold Front at High Spatiotemporal Resolution Using an X-Band Phased Array Imaging Radar

“…In recent years, phased-array weather radar systems have become increasingly commonplace, as attention has been drawn to advantages gained by use of beam multiplexing and agile beam steering [43][44][45][46][47]. This study makes use of the AIR, an X-band phased-array imaging radar designed and built by faculty, staff, and students at the University of Oklahoma Advanced Radar Research Center (OU ARRC) [48]. Because the AIR is an imaging radar, a fan beam is transmitted in elevation, with each of the 36 elements recording a stream of I/Q data on receive (32 elements were used in this case).…”

“…However, this does not significantly affect the analysis from this case. The 3-dB transmit beamwidth of the AIR is 20 • in elevation and 1 • in azimuth; this beam configuration is typically referred to as a fan beam [48]. The use of fan beams in imaging radars allows for data to be simultaneously recorded for multiple locations in the scanning domain.…”

“…Due to a 2% duty cycle limitation, the PRT was chosen to be 757 µs, corresponding to a Nyquist velocity of 10.4 m·s −1 . Digital beamforming offers several advantages over more traditional 'pencil-beam' radar VCPs, mainly in generating simultaneous RHIs, such that vertical advection is not an issue [47,48,56,57]. Additionally, the AIR offers significant processing flexibility (adjustable temporal sampling and beamforming type for sensitivity and clutter mitigation).…”

Mitigation Techniques to Reduce the Impact of Wind Turbines on Radar Services

“…A more advanced version of adapting the scanning strategy may be possible using phased array radars [45,46]. It has been suggested that the beam shape of the phased array radar can be altered in such a way that a null in the antenna radiation pattern is created in the direction of the wind turbine [47].…”

Three-dimensional radar imaging of atmospheric layer and turbulence structures using multiple receivers and multiple frequencies

“…With CRI and/or RIM, there have been plenty of applications to the atmosphere, such as scattering mechanisms and dynamics in polar mesosphere summer echoes (PMSE) , small-scale variability of precipitation (Palmer et al, 2006), mitigation of bird contamination (Chen et al, 2007), effect of KelvinHelmholtz instability (KHI) on mean vertical wind (Chen et al, 2008a), KHI triggered by inertia-gravity wave , imaging of equatorial spread F (Chau et al, 2008), clutter suppression (Yu et al, 2010), measurement of aspect sensitivity of refractivity irregularities (Chen and Furumoto, 2013), applications to UHF radar (Chilson et al, 2003) and mobile weather radar (Isom et al, 2013), derivation of horizontal wind velocities (Sureshbabu et al, 2013), and so on.…”