Spatial interferometer measurements with the Chung-Li VHF radar

The Chung-Li VHF radar consists of three phase-coherent transmitting-receiving antenna systems, which allow an optimum application of interferometer and incidence angle measurements of radar echoes from the troposphere and the stratosphere. We briefly describe the applications of the spatial domain interferometry and present here the first measurements of cross spectra and the corresponding phases, which vary as function of frequency due to the mean wind. We also present the first incidence angle measurements and show that the scattering-reflecting structures in the troposphere can be inclined to the horizontal by a tilt or inclination of l°–2°. We also notice a periodic change of this inclination as well as the radial velocity measured with vertical antenna beam as a function of altitude and time which we attribute to long-period waves or mountain waves. There are clear indications that the radial velocity measured with the vertical beam is diluted by the projection of the horizontal wind in the presence of inclined or tilted reflectivity structures. We also describe observations of long-period waves seen in the horizontal wind pattern, which could be of the same origin as the quasi-periodic pattern observed in the inclination and the reflectivity.