Modeling, Error Analysis, and Evaluation of Dual-Polarization Variables Obtained from Simultaneous Horizontal and Vertical Polarization Transmit Radar. Part II: Experimental Data

2010 ◽  
Vol 27 (10) ◽  
pp. 1599-1607 ◽  
Author(s):  
J. C. Hubbert ◽  
S. M. Ellis ◽  
M. Dixon ◽  
G. Meymaris
Keyword(s):  
Experimental Data ◽  
Electric Fields ◽  
Doppler Radar ◽  
Cross Coupling ◽  
Analysis And Evaluation ◽  
Close Time ◽  
Nonzero Mean ◽  
Antenna Polarization ◽  
Radar Part ◽  
Differential Reflectivity

Abstract In this second article in a two-part work, the biases of weather radar polarimetric variables from simultaneous horizontally and vertically transmit (SHV) data are investigated. The biases are caused by cross coupling of the simultaneously transmitted vertical (V) and horizontal (H) electric fields. There are two primary causes of cross coupling: 1) the nonzero mean canting angle of the propagation medium (e.g., canted ice crystals) and 2) antenna polarization errors. Given herein are experimental data illustrating both bias sources. In Part I, a model is developed and used to quantify cross coupling and its impact on polarization measurements. Here, in Part II, experimental data from the National Center for Atmospheric Research’s (NCAR’s) S-band dual-polarimetric Doppler radar (S-Pol) and the National Severe Storms Laboratory’s polarimetric Weather Surveillance Radar-1988 Doppler (WSR-88D), KOUN, are used to illustrate biases in differential reflectivity (Zdr). The S-Pol data are unique: both SHV data and fast alternating H and V transmit (FHV) data are gathered in close time proximity, and thus the FHV data provide “truth” for the SHV data. Specifically, the SHV Zdr bias in rain caused by antenna polarization errors is clearly demonstrated by the data. This has not been shown previously in the literature.

Modeling, Error Analysis, and Evaluation of Dual-Polarization Variables Obtained from Simultaneous Horizontal and Vertical Polarization Transmit Radar. Part I: Modeling and Antenna Errors

2010 ◽  
Vol 27 (10) ◽  
pp. 1583-1598 ◽  
Author(s):  
J. C. Hubbert ◽  
S. M. Ellis ◽  
M. Dixon ◽  
G. Meymaris
Keyword(s):  
Phase Difference ◽  
Doppler Radar ◽  
Cross Coupling ◽  
Dual Polarization ◽  
Scattering Model ◽  
Radar Scattering ◽  
Linear Depolarization Ratio ◽  
Antenna Polarization ◽  
Radar Part ◽  
Differential Reflectivity

Abstract In this two-part paper the biases of polarimetric variables from simultaneous horizontally and vertically transmitted (SHV) data are investigated. Here, in Part I, a radar-scattering model is developed and antenna polarization errors are investigated and estimated. In Part II, experimental data from the National Center for Atmospheric Research S-band dual-polarization Doppler radar (S-Pol) and the National Severe Storms Laboratory polarimetric Weather Surveillance Radar-1988 Doppler (WSR-88D) radar, KOUN, are used to illustrate biases in differential reflectivity (Zdr). The biases in the SHV polarimetric variables are caused by cross coupling of the horizontally (H) and vertically (V) polarized signals. The cross coupling is caused by the following two primary sources: 1) the nonzero mean canting angle of the propagation medium and 2) antenna polarization errors. The biases are strong functions of the differential propagation phase (ϕdp) and the phase difference between the H and V transmitted field components. The radar-scattering model developed here allows for the evaluation of biases caused by cross coupling as a function of ϕdp, with the transmission phase difference as a parameter. Also, antenna polarization errors are estimated using solar scan measurements in combination with estimates of the radar system’s linear depolarization ratio (LDR) measurement limit. Plots are given that show expected biases in SHV Zdr for various values of the LDR system’s limit.

Depolarization in Ice Crystals and Its Effect on Radar Polarimetric Measurements

2007 ◽  
Vol 24 (7) ◽  
pp. 1256-1267 ◽  
Author(s):  
Alexander V. Ryzhkov ◽  
Dusan S. Zrnić
Keyword(s):  
Electric Fields ◽  
Cross Coupling ◽  
Ice Crystals ◽  
Differential Phase ◽  
Polarized Waves ◽  
Strong Electric Fields ◽  
Snow Crystals ◽  
Differential Reflectivity ◽  
Simultaneous Transmission ◽  
Propagation Media

Abstract Simultaneous transmission and reception of horizontally and vertically polarized waves is a preferable choice technique for dual-polarization weather radar. One of the consequences of such a choice is possible cross-coupling between orthogonally polarized waves. Cross-coupling depends on depolarizing properties of propagation media, and it is usually negligible in rain because the net mean canting angle of raindrops is close to zero. Snow crystals at the tops of thunderstorm clouds are often canted in the presence of strong electric fields and produce noticeable cross-coupling between radar signals at horizontal and vertical polarizations if both signals are transmitted and received simultaneously. As a result, peculiar-looking radial signatures of differential reflectivity ZDR and differential phase ΦDP are commonly observed in the crystal regions of thunderstorms. The paper presents examples of strong depolarization in oriented crystals from the data collected by the polarimetric prototype of the Weather Surveillance Radar-1988 Doppler (WSR-88D) and a theoretical model that explains the results of measurements. It is shown that the sign and magnitude of the ZDR and ΦDP signatures strongly depend on the orientation of crystals and a system differential phase on transmission.

X-Band Polarimetric Observations of Cross Coupling in the Ice Phase of Convective Storms in Taiwan

2014 ◽  
Vol 53 (6) ◽  
pp. 1678-1695 ◽  
Author(s):  
J. C. Hubbert ◽  
S. M. Ellis ◽  
W.-Y. Chang ◽  
Y.-C. Liou
Keyword(s):  
Electric Fields ◽  
Cross Coupling ◽  
Radar Data ◽  
Ice Crystals ◽  
Polarimetric Radar ◽  
Differential Phase ◽  
X Band ◽  
Linear Depolarization Ratio ◽  
Differential Reflectivity ◽  
Ice Phase

AbstractIn this paper, experimental X-band polarimetric radar data from simultaneous transmission of horizontal (H) and vertical (V) polarizations (SHV) are shown, modeled, and microphysically interpreted. Both range–height indicator data and vertical-pointing X-band data from the Taiwan Experimental Atmospheric Mobile-Radar (TEAM-R) are presented. Some of the given X-band data are biased, which is very likely caused by cross coupling of the H and V transmitted waves as a result of aligned, canted ice crystals. Modeled SHV data are used to explain the observed polarimetric signatures. Coincident data from the National Center for Atmospheric Research S-band polarimetric radar (S-Pol) are presented to augment and support the X-band polarimetric observations and interpretations. The polarimetric S-Pol data are obtained via fast-alternating transmission of horizontal and vertical polarizations (FHV), and thus the S-band data are not contaminated by the cross coupling (except the linear depolarization ratio LDR) observed in the X-band data. The radar data reveal that there are regions in the ice phase where electric fields are apparently aligning ice crystals near vertically and thus causing negative specific differential phase Kdp. The vertical-pointing data also indicate the presence of preferentially aligned ice crystals that cause differential reflectivity Zdr and differential phase ϕdp to be strong functions of azimuth angle.

scholarly journals 50 MHz continuous wave interferometer observations of the unstable mid-latitude E-region ionosphere

2003 ◽  
Vol 21 (7) ◽  
pp. 1589-1600 ◽  
Author(s):  
C. Haldoupis ◽  
A. Bourdillon ◽  
A. Kamburelis ◽  
G. C. Hussey ◽  
J. A. Koehler
Keyword(s):  
Electric Fields ◽  
Continuous Wave ◽  
Isotropic Turbulence ◽  
Doppler Radar ◽  
Active Regions ◽  
Field Of View ◽  
Ionosphere Plasma ◽  
First Results ◽  
Sporadic E

Abstract. In this paper we describe the conversion of SESCAT (Sporadic-E SCATter experiment), a bistatic 50 MHz continuous wave (CW) Doppler radar located on the island of Crete, Greece, to a single (east-west) baseline interferometer. The first results show that SESCAT, which provides high quality Doppler spectra and excellent temporal resolution, has its measurement capabilities enhanced significantly when operated as an interferometer, as it can also study short-term dynamics of localized scattering regions within mid-latitude sporadic E-layers. The interferometric observations reveal that the aspect sensitive area viewed by the radar often contains a few zonally located backscatter regions, presumably blobs or patches of unstable metallic ion plasma, which drift across the radar field-of-view with the neutral wind. On average, these active regions of backscatter have mean zonal scales ranging from a few kilometers to several tens of kilometers and drift with westward speeds from ~ 20 m/s to 100 m/s, and occasionally up to 150 m/s. The cross-spectral analysis shows that mid-latitude type 1 echoes occur much more frequently than has been previously assumed and they originate in single and rather localized areas of elevated electric fields. On the other hand, typical bursts of type 2 echoes are often found to result from two adjacent regions in azimuth undergoing the same bulk motion westwards but producing scatter of opposite Doppler polarity, a fact that contradicts the notion of isotropic turbulence to which type 2 echoes are attributed. Finally, quasi-periodic (QP) echoes are observed simply to be due to sequential unstable plasma patches or blobs which traverse across the radar field-of-view, sometimes in a wave-like fashion.Key words. Ionosphere (ionospheric irregularities; mid-latitude ionosphere; plasma waves and instabilities)

A Study on Micro Strain Electrorheological Damper Model

2007 ◽  
Author(s):  
Yaying Chen ◽  
Yu Zhu ◽  
Guanghong Duan ◽  
Jia Cheng
Keyword(s):  
Experimental Data ◽  
Electric Fields ◽  
Strain State ◽  
Constant Term ◽  
Optimal Parameters ◽  
Plastic Model ◽  
Ultra Precision ◽  
Stage System ◽  
Width Change ◽  
Gas Bearing

This paper presents experimental and theoretical model analysis of an electrorheological damper operating in the micro strain state. An ER shear damper is developed and installed on an established ultra-precision gas bearing stage system. The damper characteristics of force vs. velocity responses under various electric fields and excitation frequencies are obtained. To describe the practical damper characteristics, a modified Eyring-plastic model is proposed, which differ from the original Eyring-plastic model by adding a constant term. The constant term can compensate the curve error induced by the width change of the pre-yield hysteresis loop. Based on optimal parameters identification, the modified Eyring-plastic model fits the experimental data more closely. So it is more accurate to express the electrorheological shear damper characteristics operating in the region of micro strain.

Electrostatic Generation in Dielectric Fluids: The Viscoelectric Effect

2005 ◽  
Author(s):  
Robert T. Balmer
Keyword(s):  
Experimental Data ◽  
Electric Fields ◽  
Theoretical Basis ◽  
Fluid Motion ◽  
Irreversible Thermodynamics ◽  
Reverse Effect ◽  
Dielectric Fluids ◽  
Electrostatic Generator ◽  
New Type ◽  
Mobile Charges

Simultaneous energy transfer modes have been known to interact to produce unusual “coupled” effects. This coupling now has its theoretical basis in the concept of entropy production (or dissipation or irreversibility) central to nonequilibrium irreversible thermodynamics. Over the years, many examples of coupled phenomena have been identified and studied (thermoelectricity, electrokinetics, piezoelectricity, and so forth). Electrohydrodynamics (the effect of fluid motion on electric fields and the reverse effect of electric fields on fluid motion) can be explained as a thermodynamically coupled phenomenon characterized by the viscous and electrical properties of a fluid that contain mobile charges at the molecular (e.g., ions) or macroscopic (e.g., dust) levels. This is called the “viscoelectric” effect. In the first part of this paper we apply the concepts of irreversible thermodynamics to electrohydrodynamic systems to develop the relevant relationships. The second describes experiments carried out with a new type of Couette electrostatic generator. The resulting experimental data is then discussed in light of the coupled phenomenon relations previously developed.

scholarly journals A Robust C-Band Hydrometeor Identification Algorithm and Application to a Long-Term Polarimetric Radar Dataset

2013 ◽  
Vol 52 (9) ◽  
pp. 2162-2186 ◽  
Author(s):  
Brenda Dolan ◽  
Steven A. Rutledge ◽  
S. Lim ◽  
V. Chandrasekar ◽  
M. Thurai
Keyword(s):  
Electric Fields ◽  
Drop Diameter ◽  
Identification Algorithm ◽  
Liquid Drops ◽  
Warm Rain ◽  
Wet Snow ◽  
Vertically Aligned ◽  
Differential Reflectivity ◽  
Ice Water

AbstractA new 10-category, polarimetric-based hydrometeor identification algorithm (HID) for C band is developed from theoretical scattering simulations including wet snow, hail, and big drops/melting hail. The HID is applied to data from seven wet seasons in Darwin, Australia, using the polarimetric C-band (C-POL) radar, to investigate microphysical differences between monsoon and break periods. Scattering simulations reveal significant Mie effects with large hail (diameter > 1.5 cm), with reduced reflectivity and enhanced differential reflectivity Zdr and specific differential phase Kdp relative to those associated with S band. Wet snow is found to be associated with greatly depreciated correlation coefficient ρhv and moderate values of Zdr. It is noted that large oblate liquid drops can produce the same electromagnetic signatures at C band as melting hail falling quasi stably, resulting in some ambiguity in the HID retrievals. Application of the new HID to seven seasons of C-POL data reveals that hail and big drops/melting hail occur much more frequently during break periods than during monsoon periods. Break periods have a high frequency of vertically aligned ice above 12 km, suggesting the presence of strong electric fields. Reflectivity and mean drop diameter D0 statistics demonstrate that convective areas in both monsoon and break periods may have robust coalescence or melting precipitation ice processes, leading to enhanced reflectivity and broader distributions of D0. Conversely, for stratiform regions in both regimes, mean reflectivity decreases below the melting level, indicative of evaporative processes. Break periods also have larger ice water path fractions, indicating substantial mixed-phase precipitation generation as compared with monsoonal periods. In monsoon periods, a larger percentage of precipitation is produced through warm-rain processes.

ELECTROMAGNETIC FIELDS IN AN N‐LAYER ANISOTROPIC HALF‐SPACE

Geophysics ◽  
1967 ◽  
Vol 32 (4) ◽  
pp. 668-677 ◽  
Author(s):  
Douglas P. O’Brien ◽  
H. F. Morrison
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Plane Wave ◽  
Half Space ◽  
Electric Fields ◽  
Field Measurements ◽  
Large Scatter ◽  
Tensor Impedance ◽  
The Magnetic Field ◽  
Made In

From Maxwell’s equations and Ohm’s law for a horizontally anisotropic medium, it may be shown that two independent plane wave modes propagate perpendicular to the plane of the anisotropy. Boundary conditions at the interfaces in an n‐layered model permit the calculation, through successive matrix multiplications, of the fields at the surface in terms of the fields propagated into the basal infinite half space. Specifying the magnetic field at the surface allows the calculation of the resultant electric fields, and the calculation of the entries of a tensor impedance relationship. These calculations have been programmed for the digital computer and an interpretation of impedances obtained from field measurements may thus be made in terms of the anisotropic layering. In addition, apparent resistivities in orthogonal directions have been calculated for specific models and compared to experimental data. It is apparent that the large scatter of observed resistivities can be caused by small changes in the polarization of the magnetic field.

Interplay between Fracture and Domain Switching of Ferroelectrics

2006 ◽  
Vol 306-308 ◽  
pp. 501-510
Author(s):  
Y.Q. Cui ◽  
Wei Yang
Keyword(s):  
Experimental Data ◽  
Crack Initiation ◽  
Electric Fields ◽  
Large Scale ◽  
Inner Core ◽  
Domain Switching ◽  
Global Scale ◽  
Theoretical Predictions ◽  
T Stress ◽  
Cylindrical Inclusions

Applications of above-coercive electric fields lead to domain switching of a large or global scale. Large scale switching model is proposed to deal with load-induced domains witching in experiment. Both a discussion of crack initiation via the stress intensity factor and a discussion of crack path stability via T-stress are presented. The theoretical predictions and the experimental data roughly coincide for crack initiation, propagation and stability phenomena. Attention is also extended to consider the effect of non-uniform ferro-elastic domain switching in the vicinity of a crack. The domain switching zone is divided into a saturated inner core and an active surrounding annulus. Toughening for ferroelectrics with different poling states is estimated via Reuss type approximation. Solutions obtained according to spherical and cylindrical inclusions cover the range of experimental data.

scholarly journals Comparison of E-region electric fields observed with a sounding rocket and a Doppler radar in the Seek Campaign

1998 ◽  
Vol 25 (11) ◽  
pp. 1773-1776 ◽  
Author(s):  
Mamoru Yamamoto ◽  
Tetsuya Itsuki ◽  
Takeshi Kishimoto ◽  
Roland T. Tsunoda ◽  
Robert F. Pfaff ◽  
...  
Keyword(s):  
Electric Fields ◽  
Doppler Radar ◽  
Sounding Rocket ◽  
E Region
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