Upper stratospheric vertical wind observations using high-power VHF radar technique

Reliable atmospheric echoes have been, for the first time, discriminated from clutter echoes in the so-called “gap region” from 30 to 60 km heights. Both co-polarized (co-pol) and cross-polarized (x-pol) arrays of the Jicamarca VHF radar were used to monitor the clutter component which may enter the antenna sidelobes. While no significant spectral peaks are found in the x-pol component, signal detectability well above 3 dB is obtained in some heights where refractivity layers with thickness of 1-2 km exist in the gap region. Thus, these scatterings seem to be caused by thin turbulent layers as well as in other middle atmospheric height ranges. The amplitude of inferred vertical wind velocities increases with height and is seen to be saturated around 0.3 ms^-1 near the stratopause, suggesting saturation and dissipation process of upward propagating gravity waves