Statistics of reflectivity gradients

The statistics of radar reflectivity gradients are examined for a large number of radar patterns measured in central Alberta. It is shown that the frequency of occurrence of both the first and the second derivatives of the reflectivity factor is greater for short than long radar angles. Thus, the observed radar reflectivity field is smoother far out than close to the radar. It is estimated by extrapolation of the frequency distributions that the mean gradient in precipitation patterns is above 5 dBZ per km. A comparison between both the first and second derivatives of the reflectivity factor in down-range and in cross-range direction gives indications that a square measurement cell can eliminate the asymmetry introduced by the radar beam, resulting in more isotropic reflectivity fields. This gained isotropy, together with the correction of the biases of the reflectivity factor due to reflectivity gradients, can offer a possibility of increasing the precision of radar measurements.