Disdrometer measurements during an intense rainfall event in central Illinois - Implications for differential reflectivity radar observations
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Engineering topics
Publications and source records attributed to Direskeneli, H..
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Understanding of the natural variability of rainfall is essential in order to assess radar's ability to estimate rainfall characteristics such as rainfall rate, rainfall water content and drop size distribution parameters. The two most useful measurements of rainfall for this purpose derive from ground-based disdrometers and aircraft-borne drop size spectrometers. Accordingly, this paper examines a time series of disdrometer measurements obtained during a unique rainfall event which occurred in central Illinois on October 6, 1982. The measurements are used to predict the behavior of radar observables (reflectivity factor and differential reflectivity) for application to the estimation of rainfall parameters. The results support previous theoretical predictions (Seliga and Bringi, 1976) and experimental results (Seliga et al., 1979, 1981; Bringi et al., 1982; Hall et al., 1980; Goddard et al., 1982) based upon the differential reflectivity (ZDR) radar technique.
The dual-polarization differential-reflectivity (Z-DR) radar technique of Seliga and Bringi (1976) is used to determine rainfall rates and drop sizes over a site located at a distance of 47.1 km, and the results are analyzed using the empirical calibration relations of Seliga et al. (1983) and compared with electromechanical-disdrometer measurements. The data are presented in graphs and found to be well correlated, demonstrating the validity of the Z-DR estimates and the improvement introduced by applying the empirical relations rather than an a priori drop-size distribution.