Some Non-Precipitation Echoes as Observed by EPS-9 Radar

摘要

Echoes from regions in the atmosphere where no reflecting or scattering sources could be seen are described. Such echoes, commonly called angels, in¬clude the following types, (1) thin lines associated with wind shifts in dry fronts, and preceding squall lines and air-mass showers, (2) echoes arranged in layers aloft, (3)others which are uniform and diffuse, (4) fibrilliform echoes presumably resulting from thermals, and (5) mantle echoes which correspond to the outer boundaries of cumulus clouds. One or more of these echo types were photo¬graphed on 79% of the 37 radar operating days between 1 June and 23 July 1958. Meteorological conditions during the observations are described. First gust lines associated with scattered showers and thunderstorms are considered in some detail. Illustrations of the PPI and RHI presentations of these lines as well as wind, pressure, and temperature records are included. It is concluded that these thin lines are the boundary of mesosystems and provide another method for study of the characteristics of mesosystems.