A turbulent convection theory of radar angels

Abstract

The problem of back-scattering from invisible atmospheric sources and the near zone concept put forward by Atlas are reviewed in relation to some angels observed at Bombay and New Delhi. It is seen that the near zone concept is not applicable to these cases. It is believed that a larger radar cross-section can be obtained in the far zone case by assuming a cylindrical model of the atmospheric eddies.  Such eddies may occur in a region of turbulent convection, These air parcels consisting of homogeneous refractive medium can be treated as units for back-scattering treatment and may yield a considerably larger cross-section, A number of angels observed on PPI and REI are explained on this model, 'Angel bands' observed on REI at Delhi are found to be associated with moist layers at corresponding heights, Some particularly intense echoes observed on PPI at Bombay arc attributed to the probable existence of a break in the inversion layer over the coastal region from which the radar waves are predominantly scattered towards sea and the corrugated sea surface turn back scatters sufficient energy to reach the receiver.