Spaced-Antenna Interferometry to Locate Discrete Objects and Sub-Volume Inhomogeneities of Reflectivity

Spaced-antenna interferometry (SAI) has been proposed to measure wind, shear and turbulence, within the radar's resolution volume V6. SAI also has potential to detect and locate discrete objects and sub-volume reflectivity inhomogeneities within V6. The National Weather Center's (NWC) phased-array weather radar, called the National Weather Radar Testbed (NWRT) located in Norman, Oklahoma offers such opportunities to advance weather radar techniques. In a recent paper, Zhang and Doviak (2007) examined the capabilities of SAI to measure crossbeam wind using the NWRT. Transverse shear of the radial component of wind and anisotropic turbulence were taken into account, but the reflectivity field was assumed to be homogenous.

In this paper, we consider inhomogeneities of reflectivity within V6, as well as embedded large objects, to determine their effects on SAI measurements. Spaced-antenna interferometry is formulated to detect and locate a discrete object, sub-volume inhomogeneities, and to improve radar performance in measuring reflectivity and wind fields. Auto/cross-correlation functions and spectra are derived based on wave scattering by a large discrete object and clusters of randomly distributed precipitation particles. The antenna separation, mean wind, shear and anisotropic turbulence are all taken into account in the formulation. It is shown that incomplete beam-filling leads to an effective smaller beam and the increase in cross-correlation coefficient at zero lag. Hence, an individual object and sub-volume inhomogeneities can be detected and located by weather radar interferometry. This capability further enhances the potential application of phased-array weather radar used as multi-mission system.