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Journal ArticleDOI

Attenuation and Differential Attenuation of 5-cm-Wavelength Radiation in Melting Hail

TL;DR: In this paper, specific attenuation and specific differential attenuation of 5-cm-wavelength radiation (C band) is compared with measurements at 10-cm wavelength (S band), which are much less affected by attenuation.
Abstract: Presented are quantitative estimates of specific attenuation and specific differential attenuation of 5-cm-wavelength radiation (C band) obtained by comparison with measurements at 10-cm wavelength (S band), which are much less affected by attenuation. The data originated from two almost-collocated radars in central Oklahoma. To avoid biases in estimates, the slopes with respect to range of differences in reflectivities and differential reflectivities are assumed to represent the specific attenuations. Observations on a day with no reports of hail on the ground and on a day with large hail are contrasted. A simple one-dimensional model of melting hail is used to qualify these observations. Examples of volumetric fields of the polarimetric variables obtained at the two wavelengths are presented to illustrate that much can be learned about size, orientation, and phase of hydrometeors over volumes that play a role in precipitation formation.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the effect of temperature lapse rate, humidity, vertical air velocities, and ice particle density on the vertical profiles of the radar variables is investigated, which is performed in a framework of a steady-state, one-dimensional column model.
Abstract: Spectral (bin) microphysics models are used to simulate polarimetric radar variables in melting hail. Most computations are performed in a framework of a steady-state, one-dimensional column model. Vertical profiles of radar reflectivity factor Z, differential reflectivity ZDR, specific differential phase KDP, specific attenuationAh, and specific differential attenuationADPare modeled at S, C, and X bands for a varietyof size distributions of ice particles aloft. The impact of temperature lapse rate, humidity, vertical air velocities, and ice particle density on the vertical profiles of the radar variables is also investigated. Polarimetric radar signatures of melting hail depend on the degree of melting or the height of the radar resolution volume with respect to the freezing level, which determines the relative fractions of partially and completely melted hail (i.e.,rain).Simulatedverticalprofilesofradarvariablesareverysensitivetoradarwavelengthandtheslopeof the size distribution of hail aloft, which is correlated well with maximal hail size. Analysis of relative contributions of different parts of the hail/rain size spectrum to the radar variables allows explanations of a number of experimentally observed features such as large differences in Z of hail at the three radar wavelengths, unusually high values of ZDR at C band, and relative insensitivity of the measurements at C and X bandstothe presenceoflargehailexceeding2.5cm in diameter.ModelingresultsareconsistentwithS- and C-band polarimetric radar observations and are utilized in Part II for devising practical algorithms for hail detection and determination of hail size as well as attenuation correction and rainfall estimation in the presence of hail.

118 citations

Journal ArticleDOI
TL;DR: In this article, the authors used a multimoment bulk micro-physics scheme, in which size sorting is allowed or disallowed for hydrometeor species, in the presence of vertical wind shear.
Abstract: The low levels of supercell forward flanks commonly exhibit distinct differential reflectivity (ZDR) signatures, including the low-ZDR hail signature and the high-ZDR “arc” The ZDR arc has been previously associated with size sorting of raindrops in the presence of vertical wind shear; here this model is extended to include size sorting of hail Idealized simulations of a supercell storm observed by the Norman, Oklahoma (KOUN), polarimetric radar on 1 June 2008 are performed using a multimoment bulk microphysics scheme, in which size sorting is allowed or disallowed for hydrometeor species Several velocity–diameter relationships for the hail fall speed are considered, as well as fixed or variable bulk densities that span the graupel-to-hail spectrum A T-matrix-based emulator is used to derive polarimetric fields from the hydrometeor state variablesSize sorting of hail is found to have a dominant impact on ZDR and can result in a ZDR arc from melting hail even when size sorting is disallowed in

103 citations


Cites methods or result from "Attenuation and Differential Attenu..."

  • ...Borowska et al. (2011) and Ryzhkov et al. (2011) accounted for these characteristics of melting hail in their polarimetric emulator by utilizing linear approximations between the aspect ratio of a dry hailstone and that of a raindrop into which it eventually melts, based on the laboratory…...

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  • ...These findings extend the arguments of previous studies investigating the size-sorting mechanism in the development of the ZDR arc by implicating sorting of hail and graupel over that of rain....

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Journal ArticleDOI
TL;DR: In this article, a fuzzy-logic algorithm was proposed for detecting and determining the size of small, medium and large hailstones in the S-band dual-polarization radar-1988 Doppler (WSR-88D) systems.
Abstract: The results of theoretical modeling in Part I are utilized to develop practical recommendations for developing the algorithms for hail detection and determination of its size as well as attenuation correction and rainfall estimation in the presence of hail. A new algorithm for discrimination between small hail (with maximal size of less than 2.5 cm), large hail (with diameters between 2.5 and 5.0 cm), and giant hail with size exceeding 5.0 cm is proposed and implemented for applications with the S-band dual-polarization Weather Surveillance Radar-1988 Doppler (WSR-88D) systems. The fuzzy-logic algorithm is based on the combined use of radar reflectivity Z, differential reflectivity ZDR, and cross-correlation coefficient ρhv. The parameters of the membership functions depend on the height of the radar resolution volume with respect to the freezing level, exploiting the size-dependent melting characteristics of hailstones. The attenuation effects in melting hail are quantified in this study, and a n...

92 citations


Cites background from "Attenuation and Differential Attenu..."

  • ...This result is likely due to the fact that secondary effects (such as roughness of hailstones or abrupt changes in the shape of the particles during collisions) that lead to possible reductions of rhv are not accounted for in the models (Mirkovic et al. 2013). Nonuniform beamfilling resulting from strong vertical gradients of radar variables in severe convective storms is another possible reason for additional reduction of rhv (Ryzhkov 2007). Picca and Ryzhkov (2012) showed that the depression of rhv above the melting layer in the area of major hail growth between 2108 and 2208C may indicate the presence of giant hail with sizes exceeding 5 cm that usually grows in the wet regime....

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Journal ArticleDOI
20 Nov 2013
TL;DR: In this article, the authors describe and explain artifacts found in polarimetric radar data, such as attenuation and differential attenuation, nonuniform beam filling, depolarization streaks, and three-body scattering signatures.
Abstract: With the new data collected with polarimetric radars comes a set of new data quality issues and artifacts. It is important for these artifacts to be recognized and understood as such, thereby allowing operational meteorologists to focus on the interpretation of the physically important observations. In this third part of the series, artifacts found in polarimetric radar data are described and explained. These include attenuation and differential attenuation, nonuniform beam filling, depolarization streaks, and three-body scattering signatures. Examples of each are given, along with explanations of what they mean, and how they may be used to provide some information about a storm and its microphysics.

83 citations


Additional excerpts

  • ...Because phase measurements are unaffected by attenuation, ΦDP is extremely useful for correction of attenuation and differential attenuation (e.g., Bringi et al. 1990; Testud et al. 2000; Snyder et al. 2010; Borowska et al. 2011; Gu et al. 2011)....

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  • ...Because phase measurements are unaffected by attenuation, ΦDP is extremely useful for correction of attenuation and differential attenuation (e.g., Bringi et al. 1990; Testud et al. 2000; Snyder et al. 2010; Borowska et al. 2011; Gu et al. 2011)....

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Journal ArticleDOI
TL;DR: A tornado outbreak occurred in central Oklahoma on 10 May 2010, including two EF-4 tornadoes with enhanced Fujita scale ratings of 4 (EF-4). Tragically, three deaths were reported along with significant property damage as discussed by the authors.
Abstract: A tornado outbreak occurred in central Oklahoma on 10 May 2010, including two tornadoes with enhanced Fujita scale ratings of 4 (EF-4). Tragically, three deaths were reported along with significant property damage. Several strong and violent tornadoes occurred near Norman, Oklahoma, which is a major hub for severe storms research and is arguably one of the best observed regions of the country with multiple Doppler radars operated by both the federal government and the University of Oklahoma (OU). One of the most recent additions to the radars in Norman is the high-resolution OU Polarimetric Radar for Innovations in Meteorology and Engineering (OU-PRIME). As the name implies, the radar is used as a platform for research and education in both science and engineering studies using polarimetric radar. To facilitate usage of the system by students and faculty, OU-PRIME was constructed adjacent to the National Weather Center building on the OU research campus. On 10 May 2010, several tornadoes formed near the c...

81 citations


Cites background or methods from "Attenuation and Differential Attenu..."

  • ...Initial work with OU-PRIME has focused on comparative, multiple-wavelength studies exploiting other independent radars in Norman (e.g., Picca and Ryzhkov 2010; Borowska et al. 2011; Gu et al. 2011) and the development and implementation of advanced signal processing algorithms (Wang et al....

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  • ...Of these, the strongest two were rated enhanced Fujita scale ratings of 4 (EF-4; www.depts.ttu.edu/ weweb/F_scale/images/efsr.pdf) and both of these occurred in or near Norman (Fig....

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  • ...…with OU-PRIME has focused on comparative, multiple-wavelength studies exploiting other independent radars in Norman (e.g., Picca and Ryzhkov 2010; Borowska et al. 2011; Gu et al. 2011) and the development and implementation of advanced signal processing algorithms (Wang et al. 2008; Lei et al.…...

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  • ...OBSERVATIONS OF THE 10 MAY 2010 TORNADO OUTBREAK USING OU-PRIME Potential for New Science with High-Resolution Polarimetric Radar by RobeRt D. PalmeR, DaviD boDine, matthew Kumjian, boonleng Cheong, guifu Zhang, Qing Cao, howaRD b. bluestein, alexanDeR RyZhKov, tian-you yu, anD yaDong wang AFFILIATIONS: PalmeR, boDine, anD Zhang—School of Meteorology, and Atmospheric Radar Research Center, University of Oklahoma, Norman, Oklahoma; Kumjian, RyZhKov, anD wang— Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma; Cheong anD Cao— Atmospheric Radar Research Center, University of Oklahoma, Norman, Oklahoma; bluestein—School of Meteorology, University of Oklahoma, Norman, Oklahoma; yu—School of Electrical and Computer Engineering, and Atmospheric Radar Research Center, University of Oklahoma, Norman, Oklahoma CORRESPONDING AUTHOR: Robert D. Palmer, Atmospheric Radar Research Center, University of Oklahoma, 120 David L. Boren Blvd., Suite 4610, Norman, OK 73072 E-mail: rpalmer@ou.edu The abstract for this article can be found in this issue, following the table of contents....

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  • ...In 2003, the University of Oklahoma (OU) decided to build on the strong foundation of weather radar research in Norman by investing specifically in 10 new faculty positions, support staff, and experimental infrastructure....

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References
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Book
15 Oct 2001
TL;DR: A detailed introduction to the principles of Doppler and polarimetric radar, focusing in particular on their use in the analysis of weather systems, is provided in this article, where the authors discuss background topics such as electromagnetic scattering, polarization, and wave propagation.
Abstract: This 2001 book provides a detailed introduction to the principles of Doppler and polarimetric radar, focusing in particular on their use in the analysis of weather systems. The design features and operation of practical radar systems are highlighted throughout the book in order to illustrate important theoretical foundations. The authors begin by discussing background topics such as electromagnetic scattering, polarization, and wave propagation. They then deal in detail with the engineering aspects of pulsed Doppler polarimetric radar, including the relevant signal theory, spectral estimation techniques, and noise considerations. They close by examining a range of key applications in meteorology and remote sensing. The book will be of great use to graduate students of electrical engineering and atmospheric science as well as to practitioners involved in the applications of polarimetric radar systems.

1,043 citations


"Attenuation and Differential Attenu..." refers background in this paper

  • ...This is a classical polarimetric hail signature (Bringi and Chandrasekar 2001)....

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Journal ArticleDOI
TL;DR: In this paper, the authors developed an algorithm for ground-based polarimetric radars that is derived from those used for the spaceborne rain radar of TRMM (Tropical Rainfall Measurement Mission).
Abstract: The algorithm developed in this paper for ground-based polarimetric radars is derived from those used for the spaceborne rain radar of TRMM (Tropical Rainfall Measurement Mission)—the so-called rain profiling algorithms. The characteristic of this type of algorithm is to be nonlocal, that is, the full rain profile along the radar beam is derived from the reflectivity profile. However, to be stable such algorithms require an external constraint. In TRMM, the constraint is the total path attenuation derived from the observation of the ocean surface, which is used as a reference target. In the present algorithm, the external constraint is provided by the differential phase shift ΦDP between H and V polarizations. This is the reason for calling this new algorithm ZPHI. The inverse model on which ZPHI is based is a set of three power law relationships between A and Ze, KDP and A, and R and A, respectively (A, specific attenuation; Ze, equivalent reflectivity; R, rainfall rate). Each of these relations...

437 citations


"Attenuation and Differential Attenu..." refers background in this paper

  • ...…differential attenuation ADP, are well examined in numerous theoretical and experimental studies (e.g., Bringi et al. 1990, 2001; Carey et al. 2000; Testud et al. 2000; Zrnić et al. 2000; Le Bouar et al. 2001; Keenan et al. 2001; Gourley et al. 2007; Vulpiani et al. 2008; Tabary et al. 2009)....

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Journal ArticleDOI
TL;DR: In this paper, a unique dataset consisting of high-resolution polarimetric radar measurements and dense rain gauge and disdrometer observations collected in east-central Florida during the summer of 1998 was examined.
Abstract: A unique dataset consisting of high-resolution polarimetric radar measurements and dense rain gauge and disdrometer observations collected in east-central Florida during the summer of 1998 was examined. Comparison of the radar measurements and radar parameters computed from the disdrometer observations supported previous studies, which indicate that oscillating drops in the free atmosphere have more spherical apparent shapes in the mean than equilibrium shapes. Radar‐disdrometer comparisons improved markedly when using an empirical axis ratio relation developed from observational studies and representing more spherical drop shapes. Fixedform power-law rainfall estimators for radar reflectivity ( ZH), specific differential phase (KDP), specific differential phase‐differential reflectivity ( KDP, ZDR), and radar reflectivity‐differential reflectivity ( ZH, ZDR) were then determined using the disdrometer observations. Relations were produced for both equilibrium shapes and the empirical axis ratios. Polarimetric rainfall estimators based on more spherical shapes gave significantly improved performance. However, the improvement was largely in bias mitigation. Rainfall estimates with the ZH‐ZDR measurement pair had the highest correlation with rain gauge observations, the smallest range in bias factors from storm to storm, and the smallest root-mean-square error.

404 citations


"Attenuation and Differential Attenu..." refers background or methods in this paper

  • ...The simulations are performed for a radar wavelength of 5.45 cm and a raindrop temperature of 08C, assuming that the raindrop shape depends on its equivolume diameter as described by Brandes et al. (2002)....

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  • ...45 cm and a temperature of 08C, assuming raindrop shapes according to Brandes et al. (2002). In (a), the curves representing Eqs....

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  • ...45 cm and a raindrop temperature of 08C, assuming that the raindrop shape depends on its equivolume diameter as described by Brandes et al. (2002). The mean canting angle is assumed to be zero, and the width of the canting angle distribution is set to 108....

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  • ...45 cm and a raindrop temperature of 08C, assuming that the raindrop shape depends on its equivolume diameter as described by Brandes et al. (2002). The mean canting angle is assumed to be zero, and the width of the canting angle distribution is set to 108. The disdrometer measurements are truncated at a maximum diameter of 8 mm and therefore might contain some contribution from small hail. For the overwhelming majority of the measured drop size distributions (DSDs) we get Ah , 0.8 dB km 21 and ADP , 0.3 dB km(21). Overlaid in Fig. 1a are three mean curves describing the dependencies of Ah on Zh according to Le Bouar et al. (2001) and Zhang and Moayeri (1999):...

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Journal ArticleDOI
TL;DR: In this paper, the linear relationship between attenuation and differential propagation phase (cbDP) was investigated at three microwave frequencies corresponding to S (3.0 GHz), C (5.5 GHz), and X (10 GHz) bands.
Abstract: Propagation effects in rainfall are examined at three microwave frequencies corresponding to S (3.0 GHz), C (5.5 GHz), and X ( 10.0 GHz) bands. Attenuation at horizontal polarization, as well a s differential attenuation and differential propagation phase between horizontal (HI and vertical ( V ) polarizations are considered. It is shown that at the three frequencies both attenuation and differential attenuation are nearly linearly related to differential propagation phase ( cbDP). This is shown through simulation using ( a ) gamma raindrop size distributions (RSD) with three parameters (No, DO. m ) that are varied over a very wide range representing a variety of rainfall types, and ( b ) measured raindrop size distributions at a single location using a disdrometer. Measurements of X-band specific attenuation and S-band specific differential phase in convective rainshafts using the National Center for Atmospheric Research CP-2 radar are presented in order to experimentally demonstrate the linear relationship between attenuation and differential propagation phase. Correction procedures for reflectivity and differential reflectivity (&) are developed assuming that differential propagation phase is measured using a radar that alternately transmits H and V polarized waves with copolar reception through the same receiver and processor system. The correction procedures are not dependent on the actual rainrate profile between the radar and the range location of interest. The accuracy of the procedure depends on, (a) RSD fluctuations, (b) variability in the estimate of differential propagation phase due to measurement fluctuations, and ( c ) nonzero values of the backscatter differential phase ( & ) between H and V polarizations. Simulations are used to gauge the accuracy of correction procedures at S- and C-bands assuming 6 is negligible. The correction accuracy for attenuation at S-band is estimated to be -0.05 dB while at C-band it is estimated to be within I dB if (IDP G 60 deg). Simulations further indicate that C-band differential attenuations effects can be corrected to within -35% of the mean value.

273 citations


"Attenuation and Differential Attenu..." refers background in this paper

  • ...…at horizontal polarization Ah and specific differential attenuation ADP, are well examined in numerous theoretical and experimental studies (e.g., Bringi et al. 1990, 2001; Carey et al. 2000; Testud et al. 2000; Zrnić et al. 2000; Le Bouar et al. 2001; Keenan et al. 2001; Gourley et al. 2007;…...

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  • ...A motivating factor for the interest in attenuation is the potential to restore partially lost signals by applying a relation between the bias caused by attenuation (or differential attenuation) and differential phase (Bringi et al. 1990)....

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  • ...In rain, the ratio a 5 Ah/KDP at C band usually varies between 0.05 and 0.13 decibels per degree as reported by Bringi et al. (1990), Carey et al. (2000), Gourley et al. (2007), and Ryzhkov et al. (2007)....

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Journal ArticleDOI
TL;DR: A self-consistent, constraint-based algorithm is proposed and evaluated which extends the previous approaches in several important respects and is relatively immune to the precise drop axis ratio versus drop diameter relation.
Abstract: Quantitative use of C-band radar measurements of reflectivity (Z/sub h/) and differential reflectivity (Z/sub dr/) demands the use of accurate attenuation-correction procedures, especially in convective rain events. With the availability of differential phase measurements (/spl Phi//sub dp/) with a dual-polarized radar, it is now possible to improve and stabilize attenuation-correction schemes over earlier schemes which did not use /spl Phi//sub dp/. The recent introduction of constraint-based correction schemes using /spl Phi//sub dp/ constitute an important advance. In this paper, a self-consistent, constraint-based algorithm is proposed and evaluated which extends the previous approaches in several important respects. Radar data collected by the C-POL radar during the South China Sea Monsoon Experiment (SCSMEX) are used to illustrate the correction scheme. The corrected radar data are then compared against disdrometer-based scattering simulations, the disdrometer data being acquired during SCSMEX. A new algorithm is used to retrieve the median volume diameter from the corrected Z/sub h/, corrected Z/sub dr/, and K/sub dp/ radar measurements which is relatively immune to the precise drop axis ratio versus drop diameter relation. Histograms of the radar-retrieved D/sub 0/ compared against D/sub 0/ from disdrometer data are in remarkable good agreement lending further validity to the proposed attenuation-correction scheme, as well as to confidence in the use of C-band radar for the remote measurement of rain microphysics.

245 citations