Evidence for specular reflection from monostatic VHF radar observations of the stratosphere

The received signal obtained on the vertical antenna of the 40 MHz Sunset radar often reveals an order‐of‐magnitude enhancement over the received signal obtained nearly simultaneously on an antenna pointed 30° from the zenith. The enhancement is most pronounced in regions of the atmosphere which are hydrostatically very stable. The enhanced vertical echoes are consistent with specular or partial reflection from thin stable laminae of radio index of refraction. An order‐of‐magnitude calculation is used to show that the expected reflectivity from a thin stable layer would easily be detected by the radar.