Radar Performance Monitoring using Ground Clutter

The National Radar Program (NRP) within Meteorological Service of Canada (MSC) operates a network of 28 Weather Radars functioning 24/7. During significant meteorological events, the data from any weather radar is invaluable and treasured, providing relatively instantaneous visual data of hydro metric activity illustrating location, intensity, direction, trend, etc.. When such events occur, there is no question of the benefit and functionality of weather radars.

Unfortunately, the counter argument is also true. There are some extended time periods between meteorological events when weather radars are of little value because they indicate no data. Clear weather events lack meteorological echoes to detect. During such periods failed weather radar equipment may not be easily identified. Dependent upon the nature of the failure, "blank" data files / images may mask inoperative radars from data users. Repair crews have minimum indication of equipment problems and lose potential response time, while discovery of equipment problems may be delayed until weather reappears, which is when the system is required the most.

The MSC / NRP is suggesting equipment manufacturers could offer a built in degradation detection feature derived from ground clutter. Virtually all low angle conventional scan routines detect some amount of ground clutter in close proximity to the radar. Typically, data processors eliminate such clutter with software filters. A detection routine could intercept data containing ground clutter before filtering and derive a percentage difference of each digitized radial range bin after comparing to a historical reference. The routine would limit evaluation to ranges in close proximity of the radar, and consistently use the same low elevation scan angle (example: zero degrees). The routine would report an overall average difference between the measured and historical data for an entire 360 degree azimuth rotation. A low reported percentage indicates a close correlation; a high percentage indicates significant deviation. The approach relies on the secondary lobes of the radar's antenna establishing a constant radiation reflection pattern from the earth. Pattern changes could be an indication of a degrading or failed transmitter or receiver. The routine could also include automatic notification if established threshold levels are exceeded. Within MSC, NRP Engineering hope to launch a project with the MSC Science and Technology Radar Research Group to demonstrate such an approach, and illustrate how it reduces radar downtime and outage duration.