1ST OBSERVATION OF THE UPPER STRATOSPHERIC VERTICAL WIND VELOCITIES USING THE JICAMARCA VHF RADAR

The Jicamarca VHF radar (50 MHz) has detected atmospheric echoes in the so-called ''gap region'' from 30 to 60 km heights. These echoes are, for the first time, discriminated from clutter echoes, using both co-polarized (co-pol) and cross-polarized (x-pol) arrays to monitor the clutter component which may enter the antenna sidelobes. The atmospheric scatterings in this region are shown to be composed of refractivity layers with thickness as of 1-2 km as in other middle atmospheric height ranges, suggesting that these scatterings are caused by thin turbulent layers. The height profile of inferred vertical wind velocities indicates a wavy structure. The wave amplitude, as a whole, increases with height, suggesting the activity of upward-propagating gravity waves.