Three-body scattering produces precipitation signature of special diagnostic value

Examples are given of three-body scatter signatures produced by high reflectivity cores in thunderstorms The process consists of (1) scattering by the hydrometeors, (2) backscattering by the ground to the hydrometeors and (3) scattering by the hydrometeors to the radar When viewed on radar displays, the signatures have an elongated shape, radially aligned behind strong (60 dBZ) reflectivity cores A radar equation for echo power is developed and predicted r
^−-3
dependence of the echo power on the range between the center of scattering volume and a reflecting ground ring is confirmed by a least squares fit to actual data It is shown theoretically that mean Doppler shifts associated with three-body scatter signatures are caused by the vertical and radial components of hydrometeor velocities; this is also verified from least square fits of range profiles of measured Doppler velocities to theoretical curves based on geometrical considerations.