Siting of Doppler weather radars to shield ground targets

Weather radars are usually sited so they can survey as large an area as possible. A large surveillance area is achieved by placing the antenna as high as practical but then the radar can be blind to weather targets near the ground because of ground clutter interference. There are applications where it is necessary to have fine resolution of low altitude divergence and wind shear near the ground in regions of weak weather reflectivity. This requirement can be most conveniently satisfied when surveillance is near the radar, but it brings attention to the problem of reducing ground clutter. Although cancelers help to reduce ground target echoes, they cannot eliminate them, and reduction for scanning beams is limited to about 40 dB. Proper siting to take advantage of natural terrain and man-made shields (clutter fences) can further reduce ground clutter. Criteria are developed that relate ground target illumination to antenna characteristics, shield heights, and the distance to the shield. Both geometric optic and diffraction theory are used to estimate the effectiveness of shields.