Environmental Engineering Reference
In-Depth Information
Management Research Consortium (FRMRC)
sponsored by the Engineering and Physical
Sciences Research Council (EPSRC) under grants
GR/S76304/01 and EP/FO20511/1, with addition-
al funding from the Environment Agency (EA)/
Department for Environment, Food and Rural
Affairs (Defra) in the UK, and theNorthern Ireland
Rivers Agency (DARDNI) and Office of Public
Works (OPW), Dublin.
directly proportional to the rain rate R, and
expressions of
aR
b
have been
obtained. Attenuation correction algorithms have
been developed using the specific differential
phase (Bringi et al. 2001) when the radar beam
passes through rain-filled media, but additional
research has to be done to correct for attenuation
when the radar beampasses throughmelting snow
or mixed-phase precipitation.
the form A
ΒΌ
Conclusions
References
Many research challenges remain to be overcome
to increase the reliability of single- and dual-
polarization radar measurements to predict rain-
fall. The greatest benefits are likely to come from
work to account for the variation of the vertical
reflectivity profile, in particular when the melting
layer is at lower altitudes. This may not be a
problem in regions where the melting level is at
higher altitudes, but it is a real problem in regions
such as the UK. Polarimetric radar measurements
offer the possibility of classifying hydrometeors,
which allow the application of different rainfall
estimators and attenuation corrections within the
rain region. Difficulty still remains in estimating
rainfall rates in snow and melting snow, and
polarimetric radar measurements potentially pro-
vide advantages over conventional reflectivity
radars in discriminating hydrometeor types. How-
ever, these advantages are still to be realized
operationally in the context of precipitation esti-
mation from weather radar and their quantitative
use in hydrology. Hydrologically, the concentra-
tion of future effort on 'flood-producing' storms
over urban areas will also focus research effort on
the issue of measurements at both space and time
scales appropriate for applications over large
urban areas.
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Acknowledgement
The author would like to thank NERC for support
under HYREX (GR/GST/02/712). This study
has also been funded through the Flood Risk
