A Semi-Empirical Determination of the Shape of Cloud and Rain Drops

Pruppacher, H. R.; Pitter, Richard L.

doi:10.1175/1520-0469(1971)028<0086:asedot>2.0.co;2

Cited by 395 publications

(159 citation statements)

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“…R(K DP, Z DR ) algorithms are less affected than R(K DP ) estimators; R(Z H, Z DR ) algorithms are most robust to the axial ratio of the raindrops. The lowest rain rates arise when using the model of Pruppacher and Pitter (1971) or that of Brandes et al (2002), the highest occur with the model of Pruppacher and Beard (1970).…”

Section: Effect Of Raindrop Temperature On K Dp and Z Drmentioning

confidence: 98%

“…Table 1. S-band rain rate estimation algorithms for different raindrop-shape models at 10 • C. OG refers to Oguchi (1973), M&C refers to Morrison and Cross (1974), P&B refers Pruppacher and Beard (1970), P&P refers to Pruppacher and Pitter (1971) Table 2. C-band rain rate estimation algorithms for different raindrop-shape models at 10 • C. OG refers to Oguchi (1973), M&C refers to Morrison and Cross (1974), P&B refers Pruppacher and Beard (1970), P&P refers to Pruppacher and Pitter (1971), BR refers to Brandes et al (2002), T&B refers to Thurai and Bringi (2005).…”

Section: Effect Of Raindrop Temperature On K Dp and Z Drmentioning

confidence: 99%

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Simulation of polarimetric radar variables in rain at S-, C- and X-band wavelengths

et al. 2008

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Abstract. Polarimetric radar variables of rainfall events, like differential reflectivity Z DR , or specific differential phase K DP , are better suited for estimating rain rate R than just the reflectivity factor for horizontally polarized waves, Z H . A variety of physical and empirical approaches exist to estimate the rain rate from polarimetric radar observables. The relationships vary over a wide range with the location and the weather conditions.In this study, the polarimetric radar variables were simulated for S-, C-and X-band wavelengths in order to establish radar rainfall estimators for the alpine region of the form R(K DP ), R(Z H , Z DR ), and R(K DP , Z DR ). For the simulation drop size distributions of hundreds of 1-minute-rain episodes were obtained from 2D-Video-Distrometer measurements in the mountains of Styria, Austria. The sensitivity of the polarimetric variables to temperature is investigated, as well as the influence of different rain drop shape models -including recently published ones -on radar rainfall estimators. Finally it is shown how the polarimetric radar variables change with the elevation angle of the radar antenna.

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Section: Effect Of Raindrop Temperature On K Dp and Z Drmentioning

confidence: 98%

Section: Effect Of Raindrop Temperature On K Dp and Z Drmentioning

confidence: 99%

Simulation of polarimetric radar variables in rain at S-, C- and X-band wavelengths

et al. 2008

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“…The top item concerning cross polarization requires the data of distortion of raindrop shape from a sphere, e.g., by the famous model by Pruppacher et al [9]. The consideration of the other two items, temperature and multiple scattering, also become precise when taking acount of the distortion of drops.…”

Section: Introductionmentioning

confidence: 99%

Effect of Temperature and Multiple Scattering on Rain Attenuation of Electromagnetic Waves by a Simple Spherical Model

Setijadi¹,

Matsushima

Tanaka³

et al. 2009

PIER

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Abstract-Specific rain attenuation is discussed from the viewpoint of numerical solution for scattering and absorption of electromagnetic waves related to dielectric spheres. Special attention is paid to the quantitative evaluations considering the change of temperature and the existence of multiple scattering effect. The analysis is based on the set of Stratton's vector spherical wave functions and its addition theorem, which lead to the simultaneous linear equations for the expansion coefficients with adaptively selected truncation numbers. Computed extinction cross sections lead directly to the specific rain attenuation, where the Weibull raindrop distribution model is used. It is discussed how the dependence of the permittivity of water on temperature and frequency affects the attenuation property. Furthermore, the effect of multiple scattering is evaluated in terms of the root mean square of attenuation deviation from the simple superposition of single scattering (Mie's) coefficients. Contrary to general belief, this deviation is the highest at around the boundary between microwave and millimeter wave bands.

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“…The radar reflectivity was calibrated by comparisons between the radar and disdrometer reflectivity to check the calibration of the WSR-88D (weather surveillance radars -1988 Doppler) at Greer, South Carolina (Ulbrich and Lee, 1999). Goddard et al (1982) and Goddard and Cherry (1984) compared radar results with disdrometer results by using the axis-ratio relations of Pruppacher and Beard (1970) and Pruppacher and Pitter (1971), respectively; they found that radar measures of Z DR were 0.3 and 0.1 dB lower than the disdrometer estimates. In addition to disdrometers, there are various other ways to correct biases in radar data, such as by using the Z H -K DP implementation of the self-consistency principle, vertically pointing measurements, and comparisons of measured data and the mean Z H -Z DR relationship (Kwon et al, 2015).…”

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confidence: 99%

Dual-polarization radar rainfall estimation in Korea according to raindrop shapes obtained by using a 2-D video disdrometer

et al. 2016

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Abstract. Polarimetric measurements are sensitive to the sizes, concentrations, orientations, and shapes of raindrops. Thus, rainfall rates calculated from polarimetric radar are influenced by the raindrop shapes and canting. The mean raindrop shape can be obtained from long-term raindrop size distribution (DSD) observations, and the shapes of raindrops can play an important role in polarimetric rainfall algorithms based on differential reflectivity (Z DR ) and specific differential phase (K DP ). However, the mean raindrop shape is associated with the variation of the DSD, which can change depending on precipitation types and climatic regimes. Furthermore, these relationships have not been studied extensively on the Korean Peninsula. In this study, we present a method to find optimal polarimetric rainfall algorithms for the Korean Peninsula by using data provided by both a twodimensional video disdrometer (2DVD) and the Bislsan Sband dual-polarization radar. First, a new axis-ratio relation was developed to improve radar rainfall estimations. Second, polarimetric rainfall algorithms were derived by using different axis-ratio relations. The rain gauge data were used to represent the ground truth situation, and the estimated radar-point hourly mean rain rates obtained from the different polarimetric rainfall algorithms were compared with the hourly rain rates measured by a rain gauge. The daily calibration biases of horizontal reflectivity (Z H ) and differential reflectivity (Z DR ) were calculated by comparing Z H and Z DR radar measurements with the same parameters simulated by the 2DVD. Overall, the derived new axis ratio was similar to the existing axis ratio except for both small particles (≤ 2 mm) and large particles (≥ 5.5 mm). The shapes of raindrops obtained by the new axis-ratio relation carried out with the 2DVD were more oblate than the shapes obtained by the existing relations. The combined polarimetric rainfall relations using Z DR and K DP were more efficient than the single-parameter rainfall relation for estimated 2DVD rainfall; however, the R(Z H , Z DR ) algorithm showed the best performance for radar rainfall estimations, because the rainfall events used in the analysis consisted mainly of weak precipitation and K DP is relatively noisy at lower rain rates (≤ 10 mm h −1 ). Some of the polarimetric rainfall algorithms can be further improved by new axis-ratio relations.

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A Semi-Empirical Determination of the Shape of Cloud and Rain Drops

Cited by 395 publications

References 0 publications

Simulation of polarimetric radar variables in rain at S-, C- and X-band wavelengths

Simulation of polarimetric radar variables in rain at S-, C- and X-band wavelengths

Effect of Temperature and Multiple Scattering on Rain Attenuation of Electromagnetic Waves by a Simple Spherical Model

Dual-polarization radar rainfall estimation in Korea according to raindrop shapes obtained by using a 2-D video disdrometer

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