Radar energy fields bounce off anything in their path, including buildings, tall trees and hills.  These obstructions are known as ground clutter, and cancontaminate weather signals or obscure them.

Typically, weather radars use static maps that have already identified contaminated regions in good weather. These maps control where ground clutter filtering is applied.  But different weather conditions can change the path of the radar beam – it c

an bend downward or upward so there is more or less clutter contamination than expected in the static maps. This apparent shift of ground clutter in an active weather situation makes the static maps ineffective.

NSSL/CIMMS researchers have developed a novel ground clutter filter that was just endorsed by the NEXRAD Technical Advisory Committee for an engineering evaluation by the NWS Radar Operations Center.  The filter is called Clutter Environment Analysis using Adaptive Processing (CLEAN-AP), and performs real-time automatic detection and suppression of ground clutter in active weather situations.

The CLEAN-AP filter preserves Doppler radar velocity signatures close to the radar, important when rotation or gust fronts are detected.  Estimates of precipitation amounts are no longer contaminated and inflated using this “smart” filter.

The CLEAN-AP filter is proposed as a complete ground clutter mitigation solution for future upgrades of the WSR-88D network, following successful implementations on the National Weather Radar Testbed Phased Array Radar and on the University of Oklahoma’s OU-PRIME radar.