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| Titel |
Raindrop size distributions and radar reflectivity–rain rate relationships for radar hydrology |
| VerfasserIn |
R. Uijlenhoet, J. H. Pomeroy |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 5, no. 4 ; Nr. 5, no. 4, S.615-628 |
| Datensatznummer |
250002712
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| Publikation (Nr.) |
 copernicus.org/hess-5-615-2001.pdf |
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| Zusammenfassung |
| 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 |
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