Precipitation measurement with a C?band weather radar in southern Ontario

Abstract

Three years of seasonal radar and raindrop disdrometer data have been correlated to determine a relationship between radar reflectivity factor and rainfall rate (Z∼R) for Southern Ontario storms during rain periods. It was found that instantaneous rainfall rates for small areas can be estimated from equivalent radar reflectivity factor measurements using a best‐fit relation Z_e = 295 R^1.43 with a standard error of 0.288 in the logarithm of R. The accuracy in estimating storm rainfalls from a modest number of observations is of significance for hydrometeorological applications. The analyses revealed a correctable systematic bias in the measurements not associated with the instrument systems but accountable to atmospheric effects inherent in the standard measurement technique. Only insignificant improvements were found in the relationship by stratifying the data by synoptic or storm type. Correlation of Z and R from the drop size distributions alone shows the characteristic power law relationship comparable to that derived from the radar measurements and reveals the effects contributed by the drop size distribution variations.