Ground-based atmospheric research radar systems at the University of Massachusetts

Over the past two decades, the Microwave Remote Sensing Laboratory (MIRSL) at the University of Massachusetts has developed several specialized radar systems for a variety of atmospheric research applications spanning UHF to W-band frequencies. Presently, the laboratory routinely operates four research radar systems, with others in development. These systems are designed, constructed, and operated almost exclusively by graduate students and staff of the MIRSL laboratory, often in cooperation with researchers in meteorology or the atmospheric sciences from other universities or organizations. These mobile radars are available to the atmospheric research community through collaborative proposals or subcontracts and in some instances through lease agreements. Interested parties should contact the authors. The systems are summarized below.

The W-band mobile Doppler “Tornado” radar is a polarimetric radar operating at 95 GHz with a peak transmit power of 1 kW. Using a 1.2 m high-gain Cassegrain antenna, the radar achieves a 0.12 degree beamwidth with range resolution typically 30 m. This represents the finest spatial resolution of available mobile radar systems. The radar is fully integrated on a customized flatbed platform.

The X-Pol mobile Doppler radar is a dual-polarized X-band radar operating at 9.4 GHz with a peak transmit power of 12 kW per channel provided by a modified marine navigation radar transmitter. Often used in tandem with the W-band radar, it is deployed on a nearly identical platform. X-Pol is undergoing a conversion to a pulse-compression design using a solid-state power amplifier in place of the magnetron currently used. This is a first step in transforming to a solid-state active phased array architecture. Both X-Pol and the W-band radars recently participated in the VORTEX2 experiment on the Great Plains.

The S-band FMCW radar profiler is a very high-resolution vertical profiler resolving fine structure in the atmospheric boundary layer. It operates at 2.9 GHz with a continuous transmit power of 250 W and employs a pair of 2.4 m parabolic dish antennas. Range resolution is as fine as 2.5 m and beamwidth is 3 degrees. The radar can measure vertical velocity structure with temporal resolution of 0.2 s. The FMCW radar is deployed on a 20' flatbed truck with and integrated power system. A 915 MHz analog of this instrument employing spaced-antenna wind retrieval methods is currently in development.

The Advanced Multifrequency Radar (AMFR), is a three-frequency system (Ku-, Ka- and W-band) cloud and precipitation radar with peak transmit powers exceeding 1.5 kW, provided by three powerful Extended Interaction Klystrons. Three matched beam (0.75 degrees) antenna systems are mounted on an elevation over azimuth positioner. Pulse compression enables 30 m range resolutions, with Doppler and polarimetric variables measured simultaneously at the three frequencies. The system recently has undergone a number of improvements. Sample data are now available upon request.