Picometer differential-phase measurements in the laboratory

2006 ◽  
Author(s):  
Gautam Vasisht ◽  
E. Robert Ligon ◽  
Erik E. Bloemhof ◽  
M. Mark Colavita
Keyword(s):  
Phase Measurements ◽  
Differential Phase

A Comparative Study of Rainfall Retrievals Based on Specific Differential Phase Shifts at X- and S-Band Radar Frequencies

2006 ◽  
Vol 23 (7) ◽  
pp. 952-963 ◽  
Author(s):  
Sergey Y. Matrosov ◽  
Robert Cifelli ◽  
Patrick C. Kennedy ◽  
Steven W. Nesbitt ◽  
Steven A. Rutledge ◽  
...  
Keyword(s):  
Comparative Study ◽  
Radar Data ◽  
Drop Diameter ◽  
Horizontal Polarization ◽  
Differential Phase Shift ◽  
Phase Measurements ◽  
Differential Phase ◽  
X Band ◽  
Raindrop Size ◽  
Differential Reflectivity

Abstract A comparative study of the use of X- and S-band polarimetric radars for rainfall parameter retrievals is presented. The main advantage of X-band polarimetric measurements is the availability of reliable specific differential phase shift estimates, KDP, for lighter rainfalls when phase measurements at the S band are too noisy to produce usable KDP. Theoretical modeling with experimental raindrop size distributions indicates that due to some non-Rayleigh resonant effects, KDP values at a 3.2-cm wavelength (X band) are on average a factor of 3.7 greater than at 11 cm (S band), which is a somewhat larger difference than simple frequency scaling predicts. The non-Rayleigh effects also cause X-band horizontal polarization reflectivity, Zeh, and differential reflectivity, ZDR, to be larger than those at the S band. The differences between X- and S-band reflectivities can exceed measurement uncertainties for Zeh starting approximately at Zeh > 40 dBZ, and for ZDR when the mass-weighted drop diameter, Dm, exceeds about 2 mm. Simultaneous X- and S-band radar measurements of rainfall showed that consistent KDP estimates exceeding about 0.1° km−1 began to be possible at reflectivities greater than ∼26–30 dBZ while at the S band such estimates can generally be made if Zeh > ∼35–39 dBZ. Experimental radar data taken in light-to-moderate stratiform rainfalls with rain rates R in an interval from 2.5 to 15 mm h−1 showed availability of the KDP-based estimates of R for most of the data points at the X band while at the S band such estimates were available only for R greater than about 8–10 mm h−1. After correcting X-band differential reflectivity measurements for differential attenuation, ZDR measurements at both radar frequency bands were in good agreement with each other for Dm < 2 mm, which approximately corresponds to ZDR ≈ 1.6 dB. The ZDR-based retrievals of characteristic raindrop sizes also agreed well with in situ disdrometer measurements.

An Application of Linear Programming to Polarimetric Radar Differential Phase Processing

2013 ◽  
Vol 30 (8) ◽  
pp. 1716-1729 ◽  
Author(s):  
Scott E. Giangrande ◽  
Robert McGraw ◽  
Lei Lei
Keyword(s):  
Linear Programming ◽  
Weather Radar ◽  
Polarimetric Radar ◽  
Phase Measurements ◽  
Physical Constraints ◽  
Differential Phase ◽  
Beam Geometry ◽  
Radar Systems ◽  
Linear Programming Methods ◽  
Consistency Results

Abstract Differential phase and its range derivative KDP are of interest to several hydrological applications from weather radar systems. Despite the attractive qualities of polarimetric differential phase measurements, the usefulness of these radar measurements is potentially undermined as a consequence of measurement fluctuations and physical or beam geometry artifacts. This paper presents an application of linear programming for physical retrievals, here designed to improve estimates of differential propagation phase by allowing realistic physical constraints of monotonicity and polarimetric radar self-consistency. Results of the linear programming methods to the phase-processing problem are demonstrated at several common weather radar wavelengths (10, 5, and 3 cm).

Differential phase measurements by partial coherence interferometry

1999 ◽  
Author(s):  
Christoph K. Hitzenberger ◽  
Angela Baumgartner ◽  
Harald Sattmann ◽  
Adolf F. Fercher
Keyword(s):  
Partial Coherence ◽  
Phase Measurements ◽  
Differential Phase ◽  
Partial Coherence Interferometry

Ionospheric electron content measurements during "Waterhole"

1981 ◽  
Vol 59 (8) ◽  
pp. 1170-1174 ◽  
Author(s):  
J. W. MacDougall ◽  
J. A. Fulford ◽  
P. A. Forsyth
Keyword(s):  
Magnetic Field ◽  
Electron Concentration ◽  
Electron Content ◽  
Particle Precipitation ◽  
Phase Measurements ◽  
Differential Phase ◽  
Ionospheric Electron Content ◽  
E Region ◽  
Field Lines ◽  
Radio Measurements

The "Waterhole" experiment is described elsewhere by Whalen et al. This paper describes the somewhat surprising results obtained from the differential phase measurements made during the experiment. While there is evidence that the electron concentration in the immediate neighborhood of the explosion dropped as expected, the more dramatic outcome was the sudden cessation of particle precipitation. The radio measurements show that the electron concentration in the E-region below the "hole" began to decay at the time of the explosion with a rate which is consistent with recombination. It continued to decay over the time that it could be observed, about 2.5 min. It must be concluded that the particle precipitation along magnetic field lines through the hole was cut off for at least that length of time.

scholarly journals Evaluation of Attenuation Correction Methodology for Dual-Polarization Radars: Application to X-Band Systems

2005 ◽  
Vol 22 (8) ◽  
pp. 1195-1206 ◽  
Author(s):  
Eugenio Gorgucci ◽  
V. Chandrasekar
Keyword(s):  
Attenuation Correction ◽  
High Frequency ◽  
Lower Cost ◽  
Dual Polarization ◽  
Phase Measurements ◽  
Differential Phase ◽  
High Frequency Radar ◽  
Radar Systems ◽  
X Band ◽  
The Impact

Abstract Monitoring of precipitation using high-frequency radar systems, such as the X band, is becoming increasingly popular because of their lower cost compared to their S-band counterpart. However, at higher frequencies, such as the X band, the precipitation-induced attenuation is significant, and introduces ambiguities in the interpretation of the radar observations. Differential phase measurements have been shown to be very useful for correcting the measured reflectivity for precipitation-induced attenuation. This paper presents a quantitative evaluation of two attenuation correction methodologies with specific emphasis on the X band. A simple differential phase–based algorithm as well as the range-profiling algorithm are studied. The impact of backscatter differential phase on the performance of attenuation correction is evaluated. It is shown that both of the algorithms for attenuation correction work fairly well, yielding attenuation-accurate corrected reflectivities with a negligible bias.

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