Non-Precipitation Echoes

Summary of Non-Precipitation Echoes

Sunrise/sunset spikes
Ground clutter
Anomalous propagation
Radar Calibration and Testing
Range folding
Sea Breeze Fronts
Wind Power Turbines and "Wind Farms"

Anomalous Propagation (AP)

Anomalous propagation of radar echoes refers to meteorological situations where a signal comes back to the radar  antenna  even in the absence of precipitation.  In many cases it occurs when atmospheric conditions are favorable for superrefraction.

The following loop shows a region of AP; note the blue-gray region of echoes that forms then disappears southeast of Billings, MT. No precipitation was noted at KBIL, nor were showers or virga reported to the southeast

KBIL 162056Z 22014KT 10SM BKN070 04/M08 A3013 RMK AO2 SLP230 ACSL DSNT N-E T00441078 56023
KBIL 161956Z 22015KT 10SM BKN065 04/M07 A3015 RMK AO2 SLP236 ACSL NE-E T00391072
KBIL 161856Z 22015KT 10SM BKN070 03/M08 A3017 RMK AO2 SLP246 ACSL W-E T00281083
KBIL 161756Z 22014KT 10SM BKN070 BKN095 01/M09 A3021 RMK AO2 SLP261 T00061089 10006 21039 58003
KBIL 161656Z 21013KT 10SM BKN060 BKN090 M01/M10 A3022 RMK AO2 SLP266 T10061100
KBIL 161556Z 20012KT 10SM BKN095 M02/M09 A3022 RMK AO2 SLP268 T10171094

Visible satellite images indicated mountain waves, but not widespread precipitation-producing clouds.

Nearby soundings from North Platte, Nebraska and Rapid City, South Dakota showed pronounced inversions which could contribute to supperrefraction.

Another example of AP.