Fractals, Raindrops and Resolution Dependence of Rain Measurements

Large (128 × 128 cm) pieces of chemically treated blotting paper were exposed to rain and both the size and position of the drops were determined. Analyses were performed indicating that the spatial distribution is fractal. This implies that drops cluster over all the observed scales and, hence, that backscattered microwave radiation from weather radars will have a degree of coherent scattering and a systematic dependence on the measurement resolution not accounted for in the standard theory. This was quantified by two scaling exponents, and a scheme to correct radar measurements for these fractal effects was developed.