On a more consistent definition of radar reflectivity

R. FRAILE, M. FERNÁNDEZ RAGA

Abstract

Measuring radar reflectivity as 10 log10Z is inhomogeneous, since the argument of the logarithm is not dimensionless. Consequently, measurements in dBZ depend on the units used to measure Z. This study, in contrast, suggests an expression of the type 10 log10 (Z/Z0). An adequate selection of the constant Z0 (10-18 m3) will produce a redefinition that will not affect the measurements that have already been carried out and published up to now, since the result in dBZ will remain unchanged. A physical meaning has been searched for Z0in relation with parameters typical for rain. It could be considered as an indicator of the minimum daily precipitation, but this cannot be extrapolated to all types of precipitation. However, it may be affirmed that for a specific distribution of hydrometeor sizes, Z0 provides a physical reference in terms of the number and volume of raindrops.

Keywords

Precipitation, Z-R relation, Marshall and Palmer distribution

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