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| Titel |
Probabilistic approach to constrained techniques for path attenuation compensation: A numerical study for C- and X-band radars |
| VerfasserIn |
F. S. Marzano, M. Montopoli, G. Ferrauto |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250031250
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| Zusammenfassung |
| It is well established that weather radar systems operating at frequencies approximately equal
to 5 GHz or greater can suffer from rain attenuation. Rain rate estimates at these attenuated
wavelengths can be accomplished through the Hitschfeld-Bordan (HB) algorithm
(Hitschfeld and Bordan, 1954). It has been widely demonstrated that the forward
implementation of the HB alghoritm can lead to unstable solutions when the path
attenuation becomes large. The divergence associated with the HB method can be
prevented by restricting its use for light rain rates. In case of moderate to high rain rates,
the attenuation correction is typically based on constrained methods, such as the
surface reference techniques (SRT), especially developed for single frequency,
incoherent and non-polarimetric airborne weather radars (Iguchi and Meneghini,
1994). These methods uses the path integrated attenuation (PIA) as a constraint
in a manner to find a stable solution through a backward implementation of the
HB algorithm. PIA measurements are generally extracted from the echo that arise
from reference surfaces, such as mountains (for ground-base radars) or the sea (for
airborn radars). For polarimetric weather radars, PIA estimate is directly related to
ΦDP.
Different surface reference methods can be derived by adjusting different model
parameters in such a way that the path integrated attenuation calculated from the measured
Zm profile equals the estimated PIA. Then, the α-adjustment or constant-adjustment
methods can be constructed if the coefficient α in the k - Z relationship k=αZβ or the
radar constant are adjusted, respectively. Effectiveness of the constrained methods
strongly depends on the PIA estimate accuracy, especially when the path attenuation
is weak. In order to avoid inaccuracies in the attenuation correction when rain is
weak, a hybrid (HYB) of the SRT and the HB method can be used (Meneghini et al,
2000).
In this work, we focus on non-polarimetric, ground-based radar systems operating at
C-band and X-band. Following a probabilistic approach, synthetic rain profiles are generated
and comparisons among the constrained techniques for path attenuation compensation are
performed. Quantification of the accuracy and robustness of the constrained methods is also
carried out and the influence of uncertainties affecting the radar measurements, that is
uncertainties in the radar calibration, DSD parametrization and PIA estimate, is investigated. |
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