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Correcting For Terrain Interference, Attenuation, and System Bias for a Dual Polarimetric, X-Band Radar

This thesis outlines the procedure and theory used to calibrate the UMass eXperimental X-band Radar (UMAXX) for the purpose of monitoring meteorological events in the Pioneer Valley region. Due to the complex topography of the area, lower tilt angles are subject to partial or full beam blockage as well as ground clutter observed through the main beam or sidelobes. Additionally, there are biases internal and external to the system that impact the reflectivity and differential reflectivity measurements. These biases and corrections are addressed in this work. As the radar has been operational since September of 2018, there is ample data available to diag-nose and to perform the necessary corrections to the system. A variety of methods are employed to validate these corrections including comparing intersecting scan volumes between the UMAXX and nearby WSR-88Ds of the NEXRAD network as well as the use of membership functions. Key results of this work are: Ground clutter is principally identified through differential phase and secondarily through velocity and co-polar correlation Partial beam blockage is best estimated assuming a 1.67◦, 2-way beamwidth with an 8dB cutoff System differential phase and Differential Reflectivity bias are functions of az-imuth due to the radome panels. A linear relation between wet radome attenuation and rain rate is found Using an attenuation factor of a = .28 to determine path integrated attenuation improves correlation of reflectivity measurements between UMAXX and NEXRAD network. Ultimately, the goal is to establish UMAXX as a reliable and well understood benchmark with which to calibrate Raytheon’s dual-polarized phased array radar. The two radars operate in sufficiently close frequencies within X-band and collected data simultaneously while colocated. While phased arrays show great promise and potential in meteorologic observations, they come with many challenges that neces-sitate the use of a trustworthy baseline with which to validate its measurements. Additionally, UMAXX’s data is to be streamed to serve as a source to fill any gaps present in the National Weather Service’s network in the region.
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