scholarly journals Polarimetric Spectral Filter for Adaptive Clutter and Noise Suppression

2009 ◽  
Vol 26 (2) ◽  
pp. 215-228 ◽  
Author(s):  
Dmitri N. Moisseev ◽  
V. Chandrasekar
Keyword(s):  
Noise Suppression ◽  
State University ◽  
Spectral Filter ◽  
Colorado State University ◽  
Ground Clutter ◽  
Observation Volume ◽  
Spectral Decompositions ◽  
Different Types ◽  
State Water ◽  
Differential Reflectivity

Abstract In this paper, spectral decompositions of differential reflectivity, differential phase, and copolar correlation coefficient are used to discriminate between weather and nonweather signals in the spectral domain. This approach gives a greater flexibility for discrimination between different types of scattering sources present in a radar observation volume. A spectral filter, which removes nonweather signals, is defined based on this method. The performance of this filter is demonstrated on the Colorado State University–University of Chicago–Illinois State Water Survey (CSU–CHILL) observations. It is shown that the resulting filter parameters are adaptively defined for each range sample and do not require an assumption on spectral properties of ground clutter.

Performance of the Hail Differential Reflectivity (HDR) Polarimetric Radar Hail Indicator

2007 ◽  
Vol 46 (8) ◽  
pp. 1290-1301 ◽  
Author(s):  
Tracy K. Depue ◽  
Patrick C. Kennedy ◽  
Steven A. Rutledge
Keyword(s):  
Elevation Angle ◽  
Maximum Diameter ◽  
State University ◽  
Polarimetric Radar ◽  
Colorado State University ◽  
Surface Wetness ◽  
Critical Success ◽  
State Water ◽  
Linear Depolarization Ratio ◽  
Differential Reflectivity

Abstract A series of poststorm surveys were conducted in the wake of hailstorms observed by the Colorado State University–University of Chicago–Illinois State Water Survey (CSU-CHILL) S-Band polarimetric radar. Information on hail characteristics (maximum diameter, building damage, apparent hailstone density, etc.) was solicited from the general-public storm observers that were contacted during the surveys; the locations of their observations were determined using GPS equipment. Low-elevation angle radar measurements of reflectivity, differential reflectivity ZDR, and linear depolarization ratio (LDR) were interpolated to the ground-observer locations. Relationships between the hail differential reflectivity parameter HDR and the observer-reported hail characteristics were examined. It was found that HDR thresholds of 21 and 30 dB were reasonably successful (critical success index values of ∼0.77) in respectively identifying regions where large (>19 mm in diameter) and structurally damaging hail were observed. The LDR characteristics in the observed hail areas were also examined. Because of sensitivities to variations in the hailstone bulk ice density, degree of surface wetness, and shape irregularities, the basic correlation between LDR magnitude and hail diameter was poor. However, when the reported hail diameters exceeded ∼25 mm, LDR levels below ∼−24 dB were uncommon.

scholarly journals Clutter Suppression for Staggered PRT Waveforms

2008 ◽  
Vol 25 (12) ◽  
pp. 2209-2218 ◽  
Author(s):  
Dmitri N. Moisseev ◽  
Cuong M. Nguyen ◽  
V. Chandrasekar
Keyword(s):  
Time Domain ◽  
State Of The Art ◽  
Radar Signal ◽  
Clutter Suppression ◽  
State University ◽  
Spectral Moments ◽  
Colorado State University ◽  
Current State ◽  
Repetition Time ◽  
State Water

Abstract This paper presents a clutter suppression methodology for staggered pulse repetition time (PRT) observations. It is shown that spectral moments of precipitation echoes can be accurately estimated even in cases where clutter-to-signal ratios are high by using a parametric time domain method (PTDM). Based on radar signal simulations, the accuracy of the proposed method is evaluated for various observation conditions. The performance of PTDM is demonstrated by the implementation of the staggered PRT at the Colorado State University–University of Chicago–Illinois State Water Survey (CSU–CHILL). Based on this study, it is found that the accuracy of the retrieval is comparable to the current state of the art methods applied to the uniformly sampled observations and that the estimated velocity is unbiased for the complete Nyquist range.

A New Dual-Polarization Radar Rainfall Algorithm: Application in Colorado Precipitation Events

2011 ◽  
Vol 28 (3) ◽  
pp. 352-364 ◽  
Author(s):  
R. Cifelli ◽  
V. Chandrasekar ◽  
S. Lim ◽  
P. C. Kennedy ◽  
Y. Wang ◽  
...  
Keyword(s):  
Estimation Algorithm ◽  
State University ◽  
Dual Polarization ◽  
Rainfall Estimation ◽  
Radar Rainfall ◽  
Colorado State University ◽  
Differential Phase ◽  
Precipitation Estimation ◽  
The One ◽  
Differential Reflectivity

Abstract The efficacy of dual-polarization radar for quantitative precipitation estimation (QPE) has been demonstrated in a number of previous studies. Specifically, rainfall retrievals using combinations of reflectivity (Zh), differential reflectivity (Zdr), and specific differential phase (Kdp) have advantages over traditional Z–R methods because more information about the drop size distribution (DSD) and hydrometeor type are available. In addition, dual-polarization-based rain-rate estimators can better account for the presence of ice in the sampling volume. An important issue in dual-polarization rainfall estimation is determining which method to employ for a given set of polarimetric observables. For example, under what circumstances does differential phase information provide superior rain estimates relative to methods using reflectivity and differential reflectivity? At Colorado State University (CSU), an optimization algorithm has been developed and used for a number of years to estimate rainfall based on thresholds of Zh, Zdr, and Kdp. Although the algorithm has demonstrated robust performance in both tropical and midlatitude environments, results have shown that the retrieval is sensitive to the selection of the fixed thresholds. In this study, a new rainfall algorithm is developed using hydrometeor identification (HID) to guide the choice of the particular rainfall estimation algorithm. A separate HID algorithm has been developed primarily to guide the rainfall application with the hydrometeor classes, namely, all rain, mixed precipitation, and all ice. Both the data collected from the S-band Colorado State University–University of Chicago–Illinois State Water Survey (CSU–CHILL) radar and a network of rain gauges are used to evaluate the performance of the new algorithm in mixed rain and hail in Colorado. The evaluation is also performed using an algorithm similar to the one developed for the Joint Polarization Experiment (JPOLE). Results show that the new CSU HID-based algorithm provides good performance for the Colorado case studies presented here.

scholarly journals Retrieval of Reflectivity in a Networked Radar Environment

2008 ◽  
Vol 25 (10) ◽  
pp. 1755-1767 ◽  
Author(s):  
V. Chandrasekar ◽  
S. Lim
Keyword(s):  
Electromagnetic Waves ◽  
State University ◽  
Colorado State University ◽  
Adaptive Sensing ◽  
Specific Attenuation ◽  
Rain Medium ◽  
X Band ◽  
State Water ◽  
Networked Radar ◽  
Using Data

Abstract A system for reflectivity and attenuation retrieval for rain medium in a networked radar environment is described. Electromagnetic waves backscattered from a common volume in networked radar systems are attenuated differently along the different paths. A solution for the specific attenuation distribution is proposed by solving the integral equation for reflectivity and attenuation. The set of governing integral equations describing the backscatter and propagation of common resolution volume are solved simultaneously with constraints on total path attenuation. The proposed algorithm is evaluated based on simulated X-band radar observations synthesized from S-band measurements collected by the Colorado State University–University of Chicago–Illinois State Water Survey (CSU–CHILL) radar. Retrieved reflectivity and specific attenuation using the proposed method show good agreement with simulated reflectivity and specific attenuation. Preliminary demonstration of the network-based retrieval using data from the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) IP-1 radar network are also presented.

scholarly journals Studies of the Polarimetric Covariance Matrix. Part II: Modeling and Polarization Errors

2003 ◽  
Vol 20 (7) ◽  
pp. 1011-1022 ◽  
Author(s):  
J. C. Hubbert ◽  
V. N. Bringi
Keyword(s):  
Covariance Matrix ◽  
Matrix Model ◽  
Model System ◽  
State University ◽  
Intense Rainfall ◽  
Colorado State University ◽  
Model Predictions ◽  
State Water ◽  
Propagation Matrix ◽  
Linear Depolarization Ratio

Abstract A polarimetric radar covariance matrix model is described to study the behavior of the co-to-cross covariances in precipitation. The 2 × 2 propagation matrix with attenuation, differential attenuation, and differential phase is coupled to the backscatter matrix leading to a propagation-modified covariance matrix model. System polarization errors are included in this model as well. This model is used to study the behavior of the magnitude and phase of the co-to-cross covariances and the linear depolarization ratio (LDR) in rainfall. It is shown that the model predictions are consistent with data collected with the Colorado State University (CSU)–University of Chicago–Illinois State Water Survey (CHILL) radar in intense rainfall. A method is also given for estimating the system polarization errors from covariance matrix data collected in intense rainfall.

scholarly journals Characterization and Evaluation of Hybrid Polarization Observation of Precipitation

2006 ◽  
Vol 23 (4) ◽  
pp. 552-572 ◽  
Author(s):  
Yanting Wang ◽  
V. Chandrasekar ◽  
V. N. Bringi
Keyword(s):  
Measurement Accuracy ◽  
State University ◽  
Cross Polarization ◽  
Hybrid Mode ◽  
Vertical Polarization ◽  
Colorado State University ◽  
Mode Of Operation ◽  
State Of Polarization ◽  
State Water ◽  
Polarization States

Abstract Transmitting an arbitrary state of polarization while receiving horizontal–vertical polarization states is termed the hybrid polarization mode of operation. A theoretical model is developed for hybrid mode dual-polarization measurements in terms of the covariance matrix under linear horizontal–vertical polarization basis. The cross polarization encountered introduces biases in the copolar parameters estimated in the hybrid mode. Such biases are investigated for different precipitation types and propagation effects resulting from hydrometeor orientation and antenna properties. Polarimetric data measured by the Colorado State University–University of Chicago–Illinois State Water Survey (CSU–CHILL) radar transmitting horizontal–vertical polarization states is alternately used to demonstrate the measurement accuracy that would be expected in different storm scenarios observed in the hybrid mode.

scholarly journals Wideband Reception and Processing for Dual-Polarization Radars with Dual Transmitters

2007 ◽  
Vol 24 (1) ◽  
pp. 95-101 ◽  
Author(s):  
Sutanay Choudhury ◽  
V. Chandrasekar
Keyword(s):  
Doppler Radar ◽  
Negative Impact ◽  
Spectral Width ◽  
Parameter Estimates ◽  
Dual Polarization ◽  
Mean Velocity ◽  
Colorado State University ◽  
State Water ◽  
Differential Reflectivity ◽  
The Impact

Abstract Oversampling pulsed Doppler radar returns at a rate larger than the pulse bandwidth, whitening the range samples, and subsequent averaging has been pursued as a potential way to decrease the measured standard deviation of signal parameter estimates. It has been shown that the application of oversampling, whitening, and subsequent averaging improves the quality of reflectivity, mean velocity, and spectral width estimates in agreement with theory. Application of this procedure to a dual-polarization radar with dual transmitters is evaluated in this paper. Oversampled data collected from the Colorado State University (CSU)-University of Chicago–Illinois State Water Survey (CHILL) radar using a wideband receiver are analyzed to evaluate the performance of dual-polarization parameter estimators, such as differential reflectivity and differential phase. The negative impact of relative phase characteristics of the transmitted pulses in two polarizations on the copolar correlation, and subsequently on polarimetric parameter estimation, is analyzed. CSU-CHILL radar’s transmitted pulse sampling capability is used to evaluate the impact of the transmitted waveform’s mismatch on whitening and estimation.

S-Band Dual-Polarization Radar Observations of Winter Storms

2011 ◽  
Vol 50 (4) ◽  
pp. 844-858 ◽  
Author(s):  
Patrick C. Kennedy ◽  
Steven A. Rutledge
Keyword(s):  
Particle Growth ◽  
Dual Polarization ◽  
Winter Storms ◽  
Radar Observations ◽  
Surface Precipitation ◽  
Colorado State University ◽  
Local Maxima ◽  
Temperature Isotherm ◽  
State Water ◽  
Differential Reflectivity

AbstractThis study is based on analyses of dual-polarization radar observations made by the 11-cm-wavelength Colorado State University–University of Chicago–Illinois State Water Survey (CSU–CHILL) system during four significant winter storms in northeastern Colorado. It was found that values of specific differential phase KDP often reached local maxima of ∼0.15°–0.4° km−1 in an elevated layer near the −15°C environmental temperature isotherm. The passage of these elevated positive KDP areas is shown to be linked to increased surface precipitation rates. Calculations using a microwave scattering model indicate that populations of highly oblate ice particles with moderate bulk densities and diameters in the ∼0.8–1.2-mm range can generate KDP (and differential reflectivity ZDR) values that are consistent with the radar observations. The persistent correlation between the enhanced KDP level and the −15°C temperature regime suggests that rapidly growing dendrites likely played a significant role in the production of the observed KDP patterns. The detection of organized regions of S-band KDP values greater than ∼0.1°–0.2° km−1 in winter storms may therefore be useful in identifying regions of active dendritic particle growth, as a precursor to aggregate snowfall.

A MODEL FOR DEVELOPING HIGH-QUALITY ONLINE COURSES: INTEGRATING A SYSTEMS APPROACH WITH LEARNING THEORY

2008 ◽  
Vol 12 (3) ◽  
Author(s):  
Maria Jean Puzziferro ◽  
Kaye Shelton
Keyword(s):  
Online Education ◽  
Design Theory ◽  
Systems Approach ◽  
Online Courses ◽  
Process Models ◽  
State University ◽  
High Quality ◽  
Colorado State University ◽  
Online Instructional Design ◽  
Online Course Development

As the demand for online education continues to increase, institutions are faced with developing process models for efficient, high-quality online course development. This paper describes a systems, team-based, approach that centers on an online instructional design theory (Active Mastery Learning) implemented at Colorado State University-Global Campus.

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