The U.S. Government operates seven distinct radar networks providing weather and aircraft surveil... more The U.S. Government operates seven distinct radar networks providing weather and aircraft surveillance for public weather services, air traffic control, and homeland defense. A next-generation, multifunction phased array radar (MPAR) concept has been proposed that could provide enhanced weather and aircraft surveillance services with potentially lower life-cycle costs than multiple single-function radar networks. As critical technology costs decrease, MPAR radars could
Bulletin of the American Meteorological Society, 2021
This article summarizes research and risk reduction that will inform acquisition decisions regard... more This article summarizes research and risk reduction that will inform acquisition decisions regarding NOAA’s future national operational weather radar network. A key alternative being evaluated is polarimetric phased-array radar (PAR). Research indicates PAR can plausibly achieve fast, adaptive volumetric scanning, with associated benefits for severe-weather warning performance. We assess these benefits using storm observations and analyses, observing system simulation experiments, and real radar-data assimilation studies. Changes in the number and/or locations of radars in the future network could improve coverage at low altitude. Analysis of benefits that might be so realized indicates the possibility for additional improvement in severe-weather and flash-flood warning performance, with associated reduction in casualties. Simulations are used to evaluate techniques for rapid volumetric scanning and assess data quality characteristics of PAR. Finally, we describe progress in develop...
For weather radars, range-oversampling processing was proposed as an effective way either to redu... more For weather radars, range-oversampling processing was proposed as an effective way either to reduce the variance of radar-variable estimates without increasing scan times or to reduce scan times without increasing the variance of estimates. Range oversampling entails acquiring the received signals at a rate L times as fast as the reciprocal of the pulse width (the conventional rate), where L is referred to as the range-oversampling factor. To accommodate the L-times-as-fast sampling, the original formulation of range-oversampling processing required a receiver filter with a bandwidth L times as wide as that of the matched filter (the conventional receiver filter). In this case, the noise at the output of the receiver filter can still be assumed to be white, resulting in a simplified formulation of the technique but also, and more important, in a more difficult practical implementation since the receiver filter in operational weather radars is typically matched to the transmitted pul...
Time series simulation is an important tool for developing and testing new signal processing algo... more Time series simulation is an important tool for developing and testing new signal processing algorithms for weather radar. The methods for simulating time series data have not changed much over the last few decades, but recent advances in computing technology call for new methods. It would seem that faster computers would make better-performing simulators less necessary, but improved technology has made comprehensive, multiday simulations feasible. Even a relatively minor performance improvement can significantly shorten the time of one of these multiday simulations. Current simulators can also be inaccurate for some sets of parameters, especially narrow spectrum widths. In this paper, three new modifications to the conventional simulators are introduced to improve accuracy and performance. Two of the modifications use thresholds to optimize both the total number of samples and the number of random variates that need to be simulated. The third modification uses an alternative method...
Adaptive range oversampling processing can be used either to reduce the variance of radar-variabl... more Adaptive range oversampling processing can be used either to reduce the variance of radar-variable estimates without increasing scan times or to reduce scan times without increasing the variance of estimates. For example, an implementation of adaptive pseudowhitening on the National Weather Radar Testbed Phased-Array Radar (NWRT PAR) led to a twofold reduction in scan times. Conversely, a proposed implementation of adaptive pseudowhitening the U.S. Next Generation Weather Radar (NEXRAD) network would reduce the variance of dual-polarization estimates while keeping current scan times. However, the original version of adaptive pseudowhitening is not compatible with radar-variable estimators for which an explicit variance expression is not readily available. One such nontraditional estimator is the hybrid spectrum-width estimator, which is currently used in the NEXRAD network. In this paper, an extension of adaptive pseudowhitening is proposed that utilizes lookup tables (rather than a...
Journal of Atmospheric and Oceanic Technology, 2015
WSR-88D superresolution data are produced with finer range and azimuth sampling and improved azim... more WSR-88D superresolution data are produced with finer range and azimuth sampling and improved azimuthal resolution as a result of a narrower effective antenna beamwidth. These characteristics afford improved detectability of weaker and more distant tornadoes by providing an enhancement of the tornadic vortex signature, which is characterized by a large low-level azimuthal Doppler velocity difference. The effective-beamwidth reduction in superresolution data is achieved by applying a tapered data window to the samples in the dwell time; thus, it comes at the expense of increased variances for all radar-variable estimates. One way to overcome this detrimental effect is through the use of range oversampling processing, which has the potential to reduce the variance of superresolution data to match that of legacy-resolution data without increasing the acquisition time. However, range-oversampling processing typically broadens the radar range weighting function and thus degrades the range...
Severe thunderstorms and their associated tornadoes pose significant threats to life and property... more Severe thunderstorms and their associated tornadoes pose significant threats to life and property, and using radar data to accurately measure the rotational velocity of circulations in thunderstorms is essential for appropriate, timely warnings. One key factor in accurately measuring circulation velocity is the azimuthal spacing between radar data points, which is referred to as the azimuthal sampling interval. Previous studies have shown that reducing the azimuthal sampling interval can aid in measuring circulation velocity; however, this comes at the price of increased computational complexity. Thus, choosing the best compromise requires knowledge of the relationship between the radar azimuthal sampling interval and the accuracy of the circulation strength as measured from the radar data. In this work, we use simulations to quantify the impact of azimuthal sampling on the strength of radar-observed circulations and show that the improvements get progressively smaller as the azimut...
The U.S. Government operates seven distinct radar networks providing weather and aircraft surveil... more The U.S. Government operates seven distinct radar networks providing weather and aircraft surveillance for public weather services, air traffic control, and homeland defense. A next-generation, multifunction phased array radar (MPAR) concept has been proposed that could provide enhanced weather and aircraft surveillance services with potentially lower life-cycle costs than multiple single-function radar networks. As critical technology costs decrease, MPAR radars could prove to be a cost-effective alternative to current surveillance radars. Because the total number of required radars would be reduced, maintenance and logistics infrastructure would be simplified. The National Weather Radar Testbed Phased-Array Radar (NWRT PAR) is an S-band phased-array radar located in Norman, Oklahoma that was established to demonstrate the MPAR concept. Since its inception, a team of scientists and engineers at the National Severe Storms Laboratory (NSSL) has been enhancing the functionality of thi...
2013 IEEE International Symposium on Phased Array Systems and Technology, 2013
ABSTRACT This paper describes the latest adaptive scanning capabilities of the National Weather R... more ABSTRACT This paper describes the latest adaptive scanning capabilities of the National Weather Radar Testbed Phased-Array Radar located in Norman, OK. Focused observations, tailored observations, and the required scheduling algorithms are introduced, and their performance is illustrated with real-data examples. It is demonstrated that adaptive scanning for weather radars has the potential to reduce revisit times and to provide meteorological data that can aid in the forecaster's warning-decision process.
The U.S. Government operates seven distinct radar networks providing weather and aircraft surveil... more The U.S. Government operates seven distinct radar networks providing weather and aircraft surveillance for public weather services, air traffic control, and homeland defense. A next-generation, multifunction phased array radar (MPAR) concept has been proposed that could provide enhanced weather and aircraft surveillance services with potentially lower life-cycle costs than multiple single-function radar networks. As critical technology costs decrease, MPAR radars could
Bulletin of the American Meteorological Society, 2021
This article summarizes research and risk reduction that will inform acquisition decisions regard... more This article summarizes research and risk reduction that will inform acquisition decisions regarding NOAA’s future national operational weather radar network. A key alternative being evaluated is polarimetric phased-array radar (PAR). Research indicates PAR can plausibly achieve fast, adaptive volumetric scanning, with associated benefits for severe-weather warning performance. We assess these benefits using storm observations and analyses, observing system simulation experiments, and real radar-data assimilation studies. Changes in the number and/or locations of radars in the future network could improve coverage at low altitude. Analysis of benefits that might be so realized indicates the possibility for additional improvement in severe-weather and flash-flood warning performance, with associated reduction in casualties. Simulations are used to evaluate techniques for rapid volumetric scanning and assess data quality characteristics of PAR. Finally, we describe progress in develop...
For weather radars, range-oversampling processing was proposed as an effective way either to redu... more For weather radars, range-oversampling processing was proposed as an effective way either to reduce the variance of radar-variable estimates without increasing scan times or to reduce scan times without increasing the variance of estimates. Range oversampling entails acquiring the received signals at a rate L times as fast as the reciprocal of the pulse width (the conventional rate), where L is referred to as the range-oversampling factor. To accommodate the L-times-as-fast sampling, the original formulation of range-oversampling processing required a receiver filter with a bandwidth L times as wide as that of the matched filter (the conventional receiver filter). In this case, the noise at the output of the receiver filter can still be assumed to be white, resulting in a simplified formulation of the technique but also, and more important, in a more difficult practical implementation since the receiver filter in operational weather radars is typically matched to the transmitted pul...
Time series simulation is an important tool for developing and testing new signal processing algo... more Time series simulation is an important tool for developing and testing new signal processing algorithms for weather radar. The methods for simulating time series data have not changed much over the last few decades, but recent advances in computing technology call for new methods. It would seem that faster computers would make better-performing simulators less necessary, but improved technology has made comprehensive, multiday simulations feasible. Even a relatively minor performance improvement can significantly shorten the time of one of these multiday simulations. Current simulators can also be inaccurate for some sets of parameters, especially narrow spectrum widths. In this paper, three new modifications to the conventional simulators are introduced to improve accuracy and performance. Two of the modifications use thresholds to optimize both the total number of samples and the number of random variates that need to be simulated. The third modification uses an alternative method...
Adaptive range oversampling processing can be used either to reduce the variance of radar-variabl... more Adaptive range oversampling processing can be used either to reduce the variance of radar-variable estimates without increasing scan times or to reduce scan times without increasing the variance of estimates. For example, an implementation of adaptive pseudowhitening on the National Weather Radar Testbed Phased-Array Radar (NWRT PAR) led to a twofold reduction in scan times. Conversely, a proposed implementation of adaptive pseudowhitening the U.S. Next Generation Weather Radar (NEXRAD) network would reduce the variance of dual-polarization estimates while keeping current scan times. However, the original version of adaptive pseudowhitening is not compatible with radar-variable estimators for which an explicit variance expression is not readily available. One such nontraditional estimator is the hybrid spectrum-width estimator, which is currently used in the NEXRAD network. In this paper, an extension of adaptive pseudowhitening is proposed that utilizes lookup tables (rather than a...
Journal of Atmospheric and Oceanic Technology, 2015
WSR-88D superresolution data are produced with finer range and azimuth sampling and improved azim... more WSR-88D superresolution data are produced with finer range and azimuth sampling and improved azimuthal resolution as a result of a narrower effective antenna beamwidth. These characteristics afford improved detectability of weaker and more distant tornadoes by providing an enhancement of the tornadic vortex signature, which is characterized by a large low-level azimuthal Doppler velocity difference. The effective-beamwidth reduction in superresolution data is achieved by applying a tapered data window to the samples in the dwell time; thus, it comes at the expense of increased variances for all radar-variable estimates. One way to overcome this detrimental effect is through the use of range oversampling processing, which has the potential to reduce the variance of superresolution data to match that of legacy-resolution data without increasing the acquisition time. However, range-oversampling processing typically broadens the radar range weighting function and thus degrades the range...
Severe thunderstorms and their associated tornadoes pose significant threats to life and property... more Severe thunderstorms and their associated tornadoes pose significant threats to life and property, and using radar data to accurately measure the rotational velocity of circulations in thunderstorms is essential for appropriate, timely warnings. One key factor in accurately measuring circulation velocity is the azimuthal spacing between radar data points, which is referred to as the azimuthal sampling interval. Previous studies have shown that reducing the azimuthal sampling interval can aid in measuring circulation velocity; however, this comes at the price of increased computational complexity. Thus, choosing the best compromise requires knowledge of the relationship between the radar azimuthal sampling interval and the accuracy of the circulation strength as measured from the radar data. In this work, we use simulations to quantify the impact of azimuthal sampling on the strength of radar-observed circulations and show that the improvements get progressively smaller as the azimut...
The U.S. Government operates seven distinct radar networks providing weather and aircraft surveil... more The U.S. Government operates seven distinct radar networks providing weather and aircraft surveillance for public weather services, air traffic control, and homeland defense. A next-generation, multifunction phased array radar (MPAR) concept has been proposed that could provide enhanced weather and aircraft surveillance services with potentially lower life-cycle costs than multiple single-function radar networks. As critical technology costs decrease, MPAR radars could prove to be a cost-effective alternative to current surveillance radars. Because the total number of required radars would be reduced, maintenance and logistics infrastructure would be simplified. The National Weather Radar Testbed Phased-Array Radar (NWRT PAR) is an S-band phased-array radar located in Norman, Oklahoma that was established to demonstrate the MPAR concept. Since its inception, a team of scientists and engineers at the National Severe Storms Laboratory (NSSL) has been enhancing the functionality of thi...
2013 IEEE International Symposium on Phased Array Systems and Technology, 2013
ABSTRACT This paper describes the latest adaptive scanning capabilities of the National Weather R... more ABSTRACT This paper describes the latest adaptive scanning capabilities of the National Weather Radar Testbed Phased-Array Radar located in Norman, OK. Focused observations, tailored observations, and the required scheduling algorithms are introduced, and their performance is illustrated with real-data examples. It is demonstrated that adaptive scanning for weather radars has the potential to reduce revisit times and to provide meteorological data that can aid in the forecaster's warning-decision process.
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Papers by Christopher Curtis