Raindrop size distributions and radar reflectivity–rain rate relationships for radar hydrology

By Remko Uijlenhoet. 2001

203 citations recorded by the source corpus.

Abstract. The conversion of the radar reflectivity factor Z(mm6m-3) to rain rate R(mm h-1 ) is a crucial step in the hydrological application of weather radar measurements. It has been common practice for over 50 years now to take for this conversion a simple power law relationship between Z and R. It is the purpose of this paper to explain that the fundamental reason for the existence of such power law relationships is the fact that Z and R are related to each other via the raindrop size distribution. To this end, the concept of the raindrop size distribution is first explained. Then, it is demonstrated that there exist two fundamentally different forms of the raindrop size distribution, one corresponding to raindrops present in a volume of air and another corresponding to those arriving at a surface. It is explained how Z and R are defined in terms of both these forms. Using the classical exponential raindrop size distribution as an example, it is demonstrated (1) that the definitions of Z and R naturally lead to power law Z–R relationships, and (2) how the coefficients of such relationships are related to the parameters of the raindrop size distribution. Numerous empirical Z–R relationships are analysed to demonstrate that there exist systematic differences in the coefficients of these relationships and the corresponding parameters of the (exponential) raindrop size distribution between different types of rainfall. Finally, six consistent Z–R relationships are derived, based upon different assumptions regarding the rain rate dependence of the parameters of the (exponential) raindrop size distribution. An appendix shows that these relationships are in fact special cases of a general Z–R relationship that follows from a recently proposed scaling framework for describing raindrop size distributions and their properties. Keywords: radar hydrology, raindrop size distribution, radar reflectivity–rain rate relationship

Subfields: Atmospheric Science, Environmental Engineering

View Paper: https://www.semanticscholar.org/paper/96d0c48180a705ddf830464fee7423f4e3ce23d0

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Atmospheric Science

Citations in the corpus

A Microphysical Interpretation of Radar Reflectivity–Rain Rate Relationships (2004, background): “…of this study is to elaborate on the potential for a microphysical interpretation of the coefﬁ-cients of the relationship between radar reﬂectivity factor Z and rain rate R, often expressed as (1) (Marshall 1969; Battan 1973; Wilson and Brandes 1979; Austin 1987; Rinehart 1997; Uijlenhoet 2001).”
Analytical solutions to sampling effects in drop size distribution measurements during stationary rainfall (2006, background): “7) and that as a result the Marshall–Palmer distribution is not self-consistent (Uijlenhoet and Stricker, 1999; Uijlenhoet, 2001).”