scholarly journals On the Possible Use of Copolar Correlation Coefficient for Improving the Drop Size Distribution Estimates at C Band

2008 ◽  
Vol 25 (10) ◽  
pp. 1873-1880 ◽  
Author(s):  
M. Thurai ◽  
D. Hudak ◽  
V. N. Bringi
Keyword(s):  
Size Distribution ◽  
Correlation Coefficient ◽  
Drop Size ◽  
Observational Evidence ◽  
Size Distributions ◽  
Dual Polarization ◽  
Simultaneous Measurements ◽  
Rain Events ◽  
Drop Size Distributions ◽  
Differential Reflectivity

Abstract A decrease in copolar correlation coefficient (ρco) at C band has been observed for several rain events with broad drop size distributions (DSDs). Observational evidence comes from simultaneous measurements with a C-band dual-polarization radar and a 2D video disdrometer. The possibility of utilizing the ρco decrease for DSD retrievals is discussed. A preliminary method using the copolar reflectivity, differential reflectivity, and ρco is given for estimating the DSD parameters. Validation is carried out by deriving the differential propagation phase (Φdp) from the estimated DSD parameters and comparing against measurements. The method presented here shows potential but needs to be further assessed in different rain climatologies.

scholarly journals Comparison of dual-polarization radar-derived and disdrometer drop-size distributions with S- and X- band radars

2017 ◽  
Author(s):  
◽  
Jordan A. Wendt
Keyword(s):  
Drop Size ◽  
Radar Data ◽  
Precipitation Event ◽  
Drop Diameter ◽  
Size Distributions ◽  
Dual Polarization ◽  
X Band ◽  
The Difference ◽  
Drop Size Distributions ◽  
Differential Reflectivity

There have been many studies on the evaluations of drop-size distributions and the parameters that affect these distributions, however, few, if any, have directly compared the relationship between the radar-derived parameters and those parameters that are disdrometer-derived. This study focuses on many different features of thunderstorms that changes the structure of the drop-size distribution (DSD) including: Horizontal reflectivity (ZH), differential reflectivity (ZDR), median drop diameter (D0), the shape parameter of the gamma-distributed DSD ([mu]), and the slope parameter of the gamma-distributed DSD (lambda). This work compares data collected by two disdrometers (OTT PARSIVEL and the Campbell Scientific Present Weather Sensor 100) against DSD parameters derived from dual-polarization radar observations. Using the Warning Decision Support System-Integrated Information (WDSS-II), radar data was merged at 1-km resolution to account for the movement of the precipitation systems before comparing to the 10-minute disdrometer data intervals. It was found that to accurately estimate DSDs from the perspective of using a weather radar, a larger precipitation event is needed. At the beginning and end of a precipitation event the difference between the radar retrieved values of D0, [mu], and [lambda] and those sampled by the disdrometer were much greater than during the middle of the event. Throughout the majority of the cases, the radar-derived reflectivity values were consistently lower than those collected by the disdrometers.

scholarly journals On the Shape–Slope Relation of Drop Size Distributions in Convective Rain

2005 ◽  
Vol 44 (7) ◽  
pp. 1146-1151 ◽  
Author(s):  
Axel Seifert
Keyword(s):  
Size Distribution ◽  
Gamma Distribution ◽  
Drop Size ◽  
Empirical Relation ◽  
Size Distributions ◽  
Shape Parameters ◽  
Raindrop Size Distribution ◽  
Raindrop Size ◽  
Drop Size Distributions ◽  
Good Agreement

Abstract The relation between the slope and shape parameters of the raindrop size distribution parameterized by a gamma distribution is examined. The comparison of results of a simple rain shaft model with an empirical relation based on disdrometer measurements at the surface shows very good agreement, but a more detailed discussion reveals some difficulties—for example, deviations from the gamma shape and the overestimation of collisional breakup.

Drop Size Distributions in Oil Water Mixtures

1973 ◽  
Vol 1973 (1) ◽  
pp. 457-465 ◽  
Author(s):  
Vijay K. Stokes ◽  
Andrew C. Harvey
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Standard Procedure ◽  
Drop Size Distribution ◽  
Coulter Counter ◽  
Size Distributions ◽  
Oil Water ◽  
Drop Size Distributions

ABSTRACT The oil drop size distribution in oil water mixtures is of importance in the design of separators that make use of settling or enhanced settling as in centrifuges. This paper describes an attempt to identify the parameters that affect the size distribution of drops in mechanically generated emulsions. Oil/water mixtures were made by three different methods. On the basis of the results of these tests, a standard procedure for making mixtures was adopted. This paper presents the results of an extensive series of tests, with three different oils, in which the drop size distributions were measured by a Coulter Counter.

Shipborne Polarimetric Weather Radar: Impact of Ship Movement on Polarimetric Variables at C Band

2014 ◽  
Vol 31 (7) ◽  
pp. 1557-1563 ◽  
Author(s):  
M. Thurai ◽  
P. T. May ◽  
A. Protat
Keyword(s):  
Drop Size ◽  
Size Distributions ◽  
Correction Factors ◽  
Distribution Parameters ◽  
Radar Measurements ◽  
Nonzero Mean ◽  
Polarimetric Weather Radar ◽  
Drop Size Distributions ◽  
Differential Reflectivity ◽  
Ship Movement

Abstract The effect of ship motion on shipborne polarimetric radar measurements is considered at C band. Calculations are carried out by (i) varying the “effective” mean canting angle and (ii) separately examining the elevation dependence. Scattering from a single oblate hydrometeor is considered at first. Equations are derived (i) to convert the measured differential reflectivity for nonzero mean canting angles to those for zero mean canting angle and (ii) to do the corresponding corrections for nonzero elevation angles. Scattering calculations are also performed using the T-matrix method with measured drop size distributions as input. Dependence on mean volume diameter is examined as well as variations of the four main polarimetric parameters. The results show that as long as the ship movement is limited to a roll of less than about 10°–15°, the effects are tolerable. Furthermore, the results from the scattering simulations have been used to provide equations for correction factors that can be applied to compensate for the “apparent” nonzero canting angles and nonzero elevation angles, so that drop size distribution parameters and rainfall rates can be estimated without any bias.

scholarly journals Approaches to radar reflectivity bias correction to improve rainfall estimation in Korea

2016 ◽  
Vol 9 (5) ◽  
pp. 2043-2053 ◽  
Author(s):  
Cheol-Hwan You ◽  
Mi-Young Kang ◽  
Dong-In Lee ◽  
Jung-Tae Lee
Keyword(s):  
Bias Correction ◽  
Drop Size ◽  
Radar Reflectivity ◽  
Size Distributions ◽  
Rainfall Estimation ◽  
Rainfall Events ◽  
Rain Events ◽  
Single Polarization ◽  
Pass Through ◽  
Drop Size Distributions

Abstract. Three methods for determining the reflectivity bias of single polarization radar using dual polarization radar reflectivity and disdrometer data (i.e., the equidistance line, overlapping area, and disdrometer methods) are proposed and evaluated for two low-pressure rainfall events that occurred over the Korean Peninsula on 25 August 2014 and 8 September 2012. Single polarization radar reflectivity was underestimated by more than 12 and 7 dB in the two rain events, respectively. All methods improved the accuracy of rainfall estimation, except for one case where drop size distributions were not observed, as the precipitation system did not pass through the disdrometer location. The use of these bias correction methods reduced the RMSE by as much as 50 %. Overall, the most accurate rainfall estimates were obtained using the overlapping area method to correct radar reflectivity.

Observed Bulk Hook Echo Drop Size Distribution Evolution in Supercell Tornadogenesis and Tornadogenesis Failure

2021 ◽  
Author(s):  
Kristofer S. Tuftedal ◽  
Michael M. French ◽  
Darrel M. Kingfield ◽  
Jeffrey C. Snyder
Keyword(s):  
Drop Size ◽  
Thermodynamic Characteristics ◽  
Radar Data ◽  
Number Concentration ◽  
Size Distributions ◽  
Polarimetric Radar ◽  
Dual Polarization ◽  
Near Surface ◽  
Microphysical Processes ◽  
Drop Size Distributions

AbstractThe time preceding supercell tornadogenesis and tornadogenesis “failure” has been studied extensively to identify differing attributes related to tornado production or lack thereof. Studies from the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX) found that air in the rear-flank downdraft (RFD) regions of non- and weakly tornadic supercells had different near-surface thermodynamic characteristics than that in strongly tornadic supercells. Subsequently, it was proposed that microphysical processes are likely to have an impact on the resulting thermodynamics of the near-surface RFD region. One way to view proxies to microphysical features, namely drop size distributions (DSDs), is through use of polarimetric radar data. Studies from the second VORTEX used data from dual-polarization radars to provide evidence of different DSDs in the hook echoes of tornadic and non-tornadic supercells. However, radar-based studies during these projects were limited to a small number of cases preventing result generalizations. This study compiles 68 tornadic and 62 non-tornadic supercells using Weather Surveillance Radar–1988 Doppler (WSR-88D) data to analyze changes in polarimetric radar variables leading up to, and at, tornadogenesis and tornadogenesis failure. Case types generally did not show notable hook echo differences in variables between sets, but did show spatial hook echo quadrant DSD differences. Consistent with past studies, differential radar reflectivity factor (ZDR) generally decreased leading up to tornadogenesis and tornadogenesis failure; in both sets, estimated total number concentration increased during the same times. Relationships between DSDs and the near-storm environment, and implications of results for nowcasting tornadogenesis, also are discussed.

Using maximum entropy approach for prediction of drop size distribution in a pilot plant multi-impeller extraction contactor

RSC Advances ◽  
2015 ◽  
Vol 5 (116) ◽  
pp. 95967-95980 ◽  
Author(s):  
Mehdi Asadollahzadeh ◽  
Meisam Torab-Mostaedi ◽  
Shahrokh Shahhosseini ◽  
Ahad Ghaemi
Keyword(s):  
Maximum Entropy ◽  
Size Distribution ◽  
Pilot Plant ◽  
Drop Size ◽  
Maximum Entropy Principle ◽  
Drop Size Distribution ◽  
Size Distributions ◽  
Entropy Principle ◽  
Drop Size Distributions ◽  
Column Extractor

In this study, the maximum entropy principle is used to predict the drop size distributions in a multi-impeller column extractor.

scholarly journals Drop Size Distribution Measurements in Outer Rainbands of Hurricane Dorian at the NASA Wallops Precipitation-Research Facility

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 578 ◽  
Author(s):  
Merhala Thurai ◽  
Viswanathan N. Bringi ◽  
David B. Wolff ◽  
David A. Marks ◽  
Charanjit S. Pabla
Keyword(s):  
Size Distribution ◽  
Drop Size ◽  
Drop Size Distribution ◽  
Size Distributions ◽  
Research Facility ◽  
Bright Band ◽  
Wet Snow ◽  
Double Moment ◽  
Dominant Process ◽  
Drop Size Distributions

Hurricane rainbands are very efficient rain producers, but details on drop size distributions are still lacking. This study focuses on the rainbands of hurricane Dorian as they traversed the densely instrumented NASA precipitation-research facility at Wallops Island, VA, over a period of 8 h. Drop size distribution (DSD) was measured using a high-resolution meteorological particle spectrometer (MPS) and 2D video disdrometer, both located inside a double-fence wind shield. The shape of the DSD was examined using double-moment normalization, and compared with similar shapes from semiarid and subtropical sites. Dorian rainbands had a superexponential shape at small normalized diameter values similar to those of the other sites. NASA’s S-band polarimetric radar performed range height-indicator (RHI) scans over the disdrometer site, showing some remarkable signatures in the melting layer (bright-band reflectivity peaks of 55 dBZ, a dip in the copolar correlation to 0.85 indicative of 12–15 mm wet snow, and a staggering reflectivity gradient above the 0 °C level of −10 dB/km, indicative of heavy aggregation). In the rain layer at heights < 2.5 km, polarimetric signatures indicated drop break-up as the dominant process, but drops as large as 5 mm were detected during the intense bright-band period.

scholarly journals Drop Size Distributions Measured by a 2D Video Disdrometer: Comparison with Dual-Polarization Radar Data

2001 ◽  
Vol 40 (6) ◽  
pp. 1019-1034 ◽  
Author(s):  
Terry J. Schuur ◽  
Alexander V. Ryzhkov ◽  
Dusan S. Zrnić ◽  
Michael Schönhuber
Keyword(s):  
Drop Size ◽  
Radar Data ◽  
Size Distributions ◽  
Dual Polarization ◽  
Drop Size Distributions
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