Why Radar Can't (Usually) See Tornadoes

Earth Curvature

Current WSR-88D scanning patterns have the lowest elevation angle as 0.5 degrees and the highest in precipitation mode scans is 19.5 degrees. Assuming the pulses go straight out from the radar (they don't), have your students make a table of distance from the radar and height off the ground.

Since our scenario is distance as we measure it, measure distance from the radar along the curvature of the earth, then go upward perpendicular to that point. This will actually increase the distance along the beam since the earth surface is curving away from the radar beam.

**Fill in the table with values you calculate**
Elevation Angle	Distance from radar	Height above ground
0.5 degrees	20 mi
	40 mi
	60 mi
	80 mi
19.5 degrees	20 mi
	40 mi
	60 mi
	80 mi

Diagram showing geometry of the problem

Last updated: March 28, 2002
Created by: DSZ