Northeast Oklahoma River/Basin Flooding
August 19, 1997

Answer to Question 9
Previous Question

Question 9. What conditions might lead to a radar's overestimate of precipitation? Underestimate?
 

 
 
Answer. WSR-88D radar may overestimate precipitation for reasons such as hail, anomalous propagation (AP) and bright band effect. These create higher reflectivities and cause an over estimation of precipitation.

Underestimation of precipitation may be caused by factors such as beam overshooting, beam broadening or an incorrect Z-R relationship. If a storm is far from the radar, it may not be visible on radar due to the beam overshooting. Also, if a storm is far from the radar, the beam may broaden and reflectivity values will be weaker than they really are.


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