Title:
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Advances in numerical analysis of precipitation reomote sensing with polarimetric radar
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Since the early use of ground radar for precipitation detection in post-world war II,
the radar has evolved on its own in precipitation remote sensing research and
applications. The recent advances in radar remote sensing is, the development of
polarimetric radar, also known as dual polarization radar, which has the capability
of transmitting electromagnetic spectrums in both horizontal (H) and vertical (V)
polarization states, thus providing additional information of the target precipitation
particles by measuring polarimetric signatures, the reflectivity factor at H
polarization (ZH) , differential reflectivity (ZDR) , differential propagation phase (ϕDP) ,
specific differential phase (KDP) , cross-correlation coefficient (PHV) and linear
depolarization ratio (LDR). In commensurate with new era in precipitation remote
sensing, this thesis explores the potential of polarimetric radar on the improvements
in precipitation remote sensing in the UK context. All major area of the
improvements aided by the polarimetry and polarimetric signatures are addressed.
These include the clutter and anomalous propagation identification, attenuation
signal correction, polarimetric rainfall estimators, drop size distribution retrievals,
bright band/melting layer recognition and hydrometeor classification. Several novel
approaches and investigations dealing with the polarimetric improvements are
scrutinized and proposed in terms of numerical analysis, while some of them employ
artificial intelligence (AI) techniques. Key original contributions in synergy with
polarimetric radar signatures on precipitation remote sensing are: 1) long-term
disdrometer DSD analysis to support the development of polarimetry based
algorithms and models, 2) the use of several AI techniques such as support vector
machine, artificial neural network, decision tree, and nearest neighbour system for
clutter identification, 3) the sensitivity a:ssociated with total differential propagation
phase constraint (ΔϕDP) on ZH correction for attenuation, 4) the exploration of
polarimetric rainfall estimators [R(ZH, ZDR, Knp)] for rainfall estimation, 5) a genetic
programming approach for drop size distribution retrievals [Do(ZH, ZDR) , Nw(ZH, ZDR,
Do), μ(ZH, ZDR, Do)], and its use for convective/stratiform rain indexing, and 6) a
fuzzy logic based system for automatic melting layer/bright band recognition and
hydrometeor classification as well as appraisal with a numerical weather prediction
(NWP) model and radio soundings observations. In fact, the radar polarimetry has
been proven not only to improve data quality and precipitation estimation, but also
characterizing the precipitation particles, thus has a great potential on fostering the
precipitation remote sensing research and applications.
Keywords: polarimetric radar; dual polarization radar; microphysics of
precipitation; drop size distribution (DSD); clutter and anomalous propagation
identification; attenuation correction; rainfall estimators; microphysical DSD
retrievals; melting layer and bright band detection; hydrometeor classification.
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