What is a hybrid scan?

The following is a general definition of hybrid scans and a brief description of the WISH Team hybrid scan methodology: The term hybrid refers to an approach in which different elevation angles are used to minimize the effects of ground clutter and data voids on radar based observations such as precipitation estimates. The term bin refers to a single radar observation valid for a polar grid cell (i.e., 1 km x 1 deg; WSR-88D). A hybrid scan is a listing of hybrid bins for the entire sweep of a radar, which extends to a given range and covers 360 deg. For each bin, a tilt index number is stored in a file ranging from 1 to x, where 1 represents the lowest elevation angle (lowest tilt) and x is some predetermined maximum angle (highest tilt number). The WISH hybrid scans use tilts 1 - 4, which corresponding to the following elevation angles: 0.5 1.5 2.4 3.4

The WISH Team hybrid scans are calculated using a high-resolution terrain dataset and the following criteria for each bin (see Figure):

• Bottom of bin must clear the ground by at least 50 meters
• There should be no more than a 60% power blockage at any ranges between the bin and the radar.

Figure. A possible hybrid scan scenario is shown for a given azimuth. Boxed-in text explains changes in the hybrid tilt number. Note this figure is not to scale.