Modeling and Interpretation of S-Band Ice Crystal Depolarization Signatures from Data Obtained by Simultaneously Transmitting Horizontally and Vertically Polarized Fields

Hubbert, J.; Ellis, Scott; Chang, Wei Yu; Rutledge, Steven A.; Dixon, Michael

doi:10.1175/jamc-d-13-0158.1

Cited by 41 publications

(43 citation statements)

References 67 publications

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“…The peak of K dp , below altitudes of higher Z DR and above altitudes of higher Z H , is a well-known but still not completely understood signature observed during snowfall (Kennedy and Rutledge, 2011;Bechini et al, 2013;Schneebeli et al, 2013;Andric et al, 2013;Hubbert et al, 2014). The proximity of this signature with respect to the −15 • C level (blue line in Fig.…”

Section: Intermediate Level Of Precipitationmentioning

confidence: 81%

“…The en- hancement is in this case moderate, with peak values mostly below 1 dB, suggesting that depositional growth is not the only process taking place and aggregation is initiated. In fact, Z DR is largely influenced by the geometry of the particles that contribute the most to the Z H signal (i.e., the biggest ones; Hubbert et al, 2014) such that the presence of even a few larger isotropic aggregates significantly decreases Z DR .…”

Section: Intermediate Level Of Precipitationmentioning

confidence: 99%

“…However, it was recognized that the concentration of dendrites needed to generate enhancements of this magnitude would lead to unreasonably high values of Z H when these crystals eventually aggregate (Andric et al, 2013). It has been demonstrated that the particles responsible for these signatures must be small compared to the radar wavelength as they were shown to behave as Rayleigh scatterers by BBC2013 and Hubbert et al (2014). BBC2013 and A2013 proposed two interesting and not mutually exclusive explanations.…”

Section: Intermediate Level Of Precipitationmentioning

confidence: 99%

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Polarimetric radar and in situ observations of riming and snowfall microphysics during CLACE 2014

et al. 2015

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Abstract. This study investigates the microphysics of winter alpine snowfall occurring in mixed-phase clouds in an inner-Alpine valley during January and February 2014. The available observations include high-resolution polarimetric radar and in situ measurements of the ice-phase and liquidphase components of clouds and precipitation. Radar-based hydrometeor classification suggests that riming is an important factor to favor an efficient growth of the precipitating mass and correlates with snow accumulation rates at ground level. The time steps during which rimed precipitation is dominant are analyzed in terms of temporal evolution and vertical structure. Snowfall identified as rimed often appears after a short time period during which the atmospheric conditions favor wind gusts and updrafts and supercooled liquid water (SLW) is available. When a turbulent atmospheric layer persists for several hours and ensures continuous SLW generation, riming can be sustained longer and large accumulations of snow at ground level can be generated. The microphysical interpretation and the meteorological situation associated with one such event are detailed in the paper. The vertical structure of polarimetric radar observations during intense snowfall classified as rimed shows a peculiar maximum of specific differential phase shift K dp , associated with large number concentrations and riming of anisotropic crystals. Below this K dp peak there is usually an enhancement in radar reflectivity Z H , proportional to the K dp enhancement and interpreted as aggregation of ice crystals. These signatures seem to be recurring during intense snowfall.

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Section: Intermediate Level Of Precipitationmentioning

confidence: 81%

Section: Intermediate Level Of Precipitationmentioning

confidence: 99%

Section: Intermediate Level Of Precipitationmentioning

confidence: 99%

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Polarimetric radar and in situ observations of riming and snowfall microphysics during CLACE 2014

et al. 2015

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“…The increased presence of the vertically aligned ice could be explained by the reported atmospheric lightning, although a straightforward relation cannot be assumed (Hubbert et al, 2014;Roberto et al, 2016). In terms of vertical ice detection, a comparison with the conventional (fuzzy logic) approach (Fig.…”

Section: Detection Performancementioning

confidence: 99%

Hydrometeor classification through statistical clustering of polarimetric radar measurements: a semi-supervised approach

et al. 2016

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Abstract. Polarimetric radar-based hydrometeor classification is the procedure of identifying different types of hydrometeors by exploiting polarimetric radar observations. The main drawback of the existing supervised classification methods, mostly based on fuzzy logic, is a significant dependency on a presumed electromagnetic behaviour of different hydrometeor types. Namely, the results of the classification largely rely upon the quality of scattering simulations. When it comes to the unsupervised approach, it lacks the constraints related to the hydrometeor microphysics. The idea of the proposed method is to compensate for these drawbacks by combining the two approaches in a way that microphysical hypotheses can, to a degree, adjust the content of the classes obtained statistically from the observations. This is done by means of an iterative approach, performed offline, which, in a statistical framework, examines clustered representative polarimetric observations by comparing them to the presumed polarimetric properties of each hydrometeor class. Aside from comparing, a routine alters the content of clusters by encouraging further statistical clustering in case of non-identification. By merging all identified clusters, the multi-dimensional polarimetric signatures of various hydrometeor types are obtained for each of the studied representative datasets, i.e. for each radar system of interest. These are depicted by sets of centroids which are then employed in operational labelling of different hydrometeors. The method has been applied on three C-band datasets, each acquired by different operational radar from the MeteoSwiss Rad4Alp network, as well as on two X-band datasets acquired by two research mobile radars. The results are discussed through a comparative analysis which includes a corresponding supervised and unsupervised approach, emphasising the operational potential of the proposed method.

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“…9 shows streaks of high positive Z DR down radial of, and negative specific differential phase K DP with low values (;0.9) of, the correlation coefficient r hv collocated with the storm's core. This is suggestive of a mixture of hail and more vertically oriented low inertia ice crystals in the presence of the storm's electrostatic field (Hubbert et al 2014). The absence of a positive Z DR or K DP signal indicates that there are no large oblate liquid state scatterers (such as large raindrops) present (Zrni c et al 1993;Ryzhkov and Zrni c 2007).…”

mentioning

confidence: 98%

Analysis of a Destructive Wind Storm on 16 November 2008 in Brisbane, Australia

Richter

Peter

Collis

2014

Monthly Weather Review

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During the late afternoon on 16 November 2008 the Brisbane (Queensland, Australia) suburb of ''The Gap'' experienced extensive wind damage caused by an intense local thunderstorm. The CP2 research radar nearby detected near-surface radial velocities exceeding 43 m s 21 above The Gap while hail size reports did not exceed golf ball size, and no tornadoes were reported. The storm environment was characterized by a layer of very moist near-surface air and strong storm-relative low-level flow, whereas the storm-relative winds aloft were weak. While the thermodynamic storm environment contained a range of downdraft-promoting ingredients such as a ;4-km-high melting level above a ;2-km-deep layer with nearly dry-adiabatic lapse rates mostly collocated with dry ambient air, a ;1-km-deep stable layer near the ground would generally lower expectations of destructive surface winds based on the downburst mechanism. Once observed reflectivities exceed 70 dBZ, downdraft cooling due to hail melting and downdraft acceleration based on hail loading are found to likely become nonnegligible forcing mechanisms. The event featured the close proximity of a hydrostatically and dynamically driven mesohigh at the base of the downdraft to a dynamically driven mesolow associated with a low-level circulation. This proximity was instrumental in the anisotropic horizontal acceleration of the nearground outflow and the ultimate strength of the Gap storm surface winds. Weak storm-relative midlevel winds are speculated to have allowed the downdraft to descend close to the low-level circulation, which set up this strong horizontal perturbation pressure gradient.

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Modeling and Interpretation of S-Band Ice Crystal Depolarization Signatures from Data Obtained by Simultaneously Transmitting Horizontally and Vertically Polarized Fields

Cited by 41 publications

References 67 publications

Polarimetric radar and in situ observations of riming and snowfall microphysics during CLACE 2014

Polarimetric radar and in situ observations of riming and snowfall microphysics during CLACE 2014

Hydrometeor classification through statistical clustering of polarimetric radar measurements: a semi-supervised approach

Analysis of a Destructive Wind Storm on 16 November 2008 in Brisbane, Australia

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