The Microwave Remote Sensing Laboratory

The Advanced Multi‑Frequency Radar’s (AMFR) capabilities are well suited for characterizing the complex microphysics of layer clouds and precipitation processes in winter storms. AMFR reflectivity and Doppler data will provide unique measurements of particle size, phase, and liquid or ice mass content that are not available from single‑frequency radar data. Demonstrations of multi‑frequency radar have shown that such information is contained in the measurements of signal extinction and from scattering differences, which result from non­Rayleigh scattering effects. Although multi‑frequency radar remote sensing techniques are reported in the literature, they are not widely used because few multi-frequency radars are available to the science community. One exception is the 33GHz/95GHz UMass Cloud Profiling Radar System (CPRS). CPRS has participated in roughly two field programs per year since its completion in 1994, and demand for its use in field research programs continues. While CPRS is a very capable system, the addition of a third lower frequency channel extends CPRS’s ability to probe precipitating clouds and facilitates multi‑frequency retrievals in mixed‑phase clouds by reducing ambiguities between attenuation and non‑Rayleigh scattering.

The AMFR will also play an important role in developing algorithms and validating measurements for an upcoming generation of space‑borne radars. The frequency bands selected for AMFR match those of several space‑borne sensors that are under development. These include the Tropical Rainfall Measuring Mission (TRMM) satellite Ku‑band (13GHz) radar, the Cloud Sat W-band (95GHz) radar, the Global Precipitation Mission (GPM) satellite radars at Ku‑band and Ka‑band (35GHz) and the second‑generation airborne rain radar (PR2) developed at NASA/JPL, which also operates at both Ku‑band and Ka‑band.

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