A Mobile Rapid-Scanning X-band Polarimetric (RaXPol) Doppler Radar System ANDREW L. PAZMANY AND JAMES B. MEAD ProSensing Inc., Amherst, Massachusetts HOWARD B. BLUESTEIN,JEFFREY C. SNYDER, AND JANA B. HOUSER School of Meteorology, University of Oklahoma, Norman, Oklahoma (Manuscript received 10 August 2012, in final form 21 December 2012) ABSTRACT A novel, rapid-scanning, X-band (3-cm wavelength), polarimetric (RaXPol), mobile radar was developed for severe-weather research. The radar employs a 2.4-m-diameter dual-polarized parabolic dish antenna on a high-speed pedestal capable of rotating the antenna at 1808 s 21 . The radar can complete a 10-elevation-step volume scan in about 20 s, while maintaining a 180-record-per-second data rate. The transmitter employs a 20-kW peak-power traveling wave tube amplifier that can generate pulse compression and frequency- hopping waveforms. Frequency hopping permits the acquisition of many more independent samples possible than without frequency hopping, making it possible to scan much more rapidly than conventional radars. Standard data products include vertically and horizontally polarized equivalent radar reflectivity factor, Doppler velocity mean and standard deviation, copolar cross-correlation coefficient, and differential phase. This paper describes the radar system and illustrates the capabilities of the radar through selected analyses of data collected in the U.S. central plains during the 2011 spring tornado season. Also noted are opportunities for experimenting with different signal-processing techniques to reduce beam smearing, increase sensitivity, and improve range resolution. 1. Introduction The need for rapidly scanning 1 weather radars for observing fast-changing weather phenomena such as convective storms, microbursts, small-scale features in hurricanes, and the process of convective development has been well established (Keeler and Frush 1983; Bluestein et al. 2001; Heinselman et al. 2012). Finescale precipitation features in severe convective storms, for example, can evolve on time scales of only tens of sec- onds or less, while conventional and research weather radars typically take 15–60 s to complete a single plan position indicator (PPI) scan. Volume scans made up of a number of PPIs at different elevation angles usually require several minutes or more to complete. Very fast- scanning military radars with electronically scanned antenna arrays have been operating for decades, but the migration of this technology to weather radars has been slow and difficult, primarily because of cost and the more demanding nature of observing meteorological targets than point targets. Fast-scanning meteorological radars have been previously developed but do not have polarimetric capabilities. Wurman and Randall (2001) developed a frequency-scanned X-band (3-cm wave- length) mobile radar, with a 2.4-m-diameter slotted waveguide array antenna, having a scan rate of 368 s 21 specifically for the study of tornadic storms. An X-band, phase/frequency electronically scanned U.S. Army air- defense radar with a 1.5 m 3 1.8 m antenna scanning at 1808 s 21 was recently converted for weather observa- tions (Bluestein et al. 2010; French et al. 2013). Also, a U.S. Navy Spy-1 S-band phased array radar was re- cently acquired by the National Severe Storms Labora- tory in Norman, Oklahoma, in order to develop adaptive beam-forming techniques for weather observations Corresponding author address: Andrew L. Pazmany, ProSensing Inc., 107 Sunderland Rd., Amherst, MA 01002. E-mail: pazmany@prosensing.com 1 The definition of ‘‘rapid scanning’’ or ‘‘rapid scan’’ depends on the user and/or the phenomenon scanned. In this paper, we mean scanning at a rate of hundreds of degrees per second rather than tens of degrees per second. 1398 JOURNAL OF ATMOSPHERIC AND OCEANIC TECHNOLOGY VOLUME 30 DOI: 10.1175/JTECH-D-12-00166.1 Ó 2013 American Meteorological Society