Observations of time dependence in the relationship between rain attenuation and depolarization in the 18- to 21.2-GHz region


  • C. E. Hendrix,

  • G. Kulon,

  • T. A. Russell


The relationship between rain attenuation and depolarization over a 7-km path was observed in about 30 separate rain events during the spring and summer of 1990. The experimental equipment was capable of measuring attenuation and cross-polarization discrimination (XPD) directly at about one measurement per second. The relationship between these two variables was found to be of the nature of a deterministic relationship but with time-varying parameters. Parameter variations appeared to be associated with rising and falling phases of rain attenuation. When successive measurements of XPD were plotted against the logarithm of attenuation, each rising or falling segment was found to follow a straight line relationship but a slightly different line for each segment. Further, in any given rain event, the slopes and intercepts of the extended straight lines were themselves highly correlated, indicating a tendency for all the lines to pass through a single point in the XPD-log attenuation plane. A simple model in which the behavior is controlled by the parameters of rain density (attenuation) and the standard deviation of canting angle of the raindrops, varying independently, appears to be consistent with the observed data.