Since 1993, the University of Massachusetts Microwave Remote Sensing Laboratory and University of Oklahoma School of Meteorology have collaborated to study severe storms and tornadoes with a 95 GHz Doppler radar [1]. To complement the high resolution, but limited range (~10 km), W-band observations with storm-scale measurements, a truck-mounted 9.4 GHz (3 cm wavelength) polarimetric Doppler radar was developed. A low cost, yet highly reliable 25 kW MK-2 Raytheon marine radar was modified to transmit equal power at vertical and horizontal polarizations [2][3] and was equipped with a dual-channel coherent-on-receive, low noise-figure (1 dB LNA noise figure) receiver. With a high-speed data system and a refurbished military pedestal mounted 6’ diameter dual-polarized antenna, the radar can continuously sample precipitation 360 deg in azimuth and 0 to 90 deg in elevation. The radar operator can choose to record the raw offset-IF time series data to compute co-pol reflectivity at H and V polarization (Zh and Zv), differential reflectivity (Zdr), specific differential phase shift (Kdp) and Doppler velocity mean and standard deviation, or averaged reflectivity in a low data rate surveillance mode of operation. During the 2001 and 2002 spring tornado season, the radar collected an extensive set of reflectivity, polarimetric and Doppler radar data from severe storms throughout the US Central Plains. The combination of fine sensitivity (0 dBZ single pulse unity SNR @ 10 km with 1 micro sec TX pulses), polarimetric and Doppler measurement capability and very low development cost (~ $20K radar RF section) make this weather radar design unique and ideally suited for network applications and small educational and research institutions. This paper will document the radar system and will present examples of long range (up to 120 km) reflectivity images of storms, Doppler velocity images of mesocyclones and Kdp data based rain rate maps.

[1] Bluestein, Howard B., Andrew L. Pazmany, 2000: Observations of Tornadoes and Other Convective Phenomena with a Mobile, 3–mm Wavelength, Doppler Radar: The Spring 1999 Field Experiment. Bulletin of the American Meteorological Society: Vol. 81, No. 12, pp. 2939–2952. [2] Seliga, T. A. and V. N. Bringi 1976: Potential Use of Radar Differential Reflectivity Measurements at Orthogonal Polarizations for Measuring Precipitation. Journal of Applied Meteorology, Vol. 15. pp. 69-75 [3] Zrnic, Dusan 1996: Simultaneous Differential Polymetric Measurement and Co-polar Correlation Coefficient Measurement. U.S. Patent# 5,500,646 Kdp data.