Since 2007 the advancement of the National Weather Radar Testbed Phased-Array Radar (NWRT PAR) hardware and software capabilities has been supporting the implementation of high-temporal-resolution (∼1 min) sampling. To achieve the increase in computational power and data archiving needs required for high-temporal-resolution sampling, the signal processor was upgraded to a scalable, Linux-based cluster with a distributed computing architecture. The development of electronic adaptive scanning, which can reduce update times by focusing data collection on significant weather, became possible through functionality added to the radar control interface and real-time controller. Signal processing techniques were implemented to address data quality issues, such as artifact removal and range-and-velocity ambiguity mitigation, absent from the NWRT PAR at its installation. The hardware and software advancements described above have made possible the development of conventional and electronic scanning capabil...

High-Temporal-Resolution Capabilities of the National Weather Radar Testbed Phased-Array Radar

The recently installed S-band phased-array radar (PAR) at the National Weather Radar Testbed (NWRT) offers fast and flexible beam steering through electronic beam forming. This capability allows the implementation of a novel scanning strategy termed beam multiplexing (BMX), with the goal of providing fast updates of weather information with high statistical accuracy. For conventional weather radar the data acquisition time for a sector scan or a volume coverage pattern (VCP) can be reduced by increasing the antenna’s rotation rate to the extent that the pedestal allows. However, statistical errors of the spectral moment estimates will increase due to the fewer samples that are available for the estimation. BMX is developed to exploit the idea of collecting independent samples and maximizing the usage of radar resources. An improvement factor is introduced to quantify the BMX performance, which is defined by the reduction in data acquisition time using BMX when the same data accuracy obtained by a...

Beam Multiplexing Using the Phased-Array Weather Radar

The recent deployment of an innovative triple pulse rise time (PRT) scheme within the French operational radar network allows for the simultaneous collection of reflectivity and radial velocity measurements up to a range of 250 km with no ambiguity. This achievement brings new perspectives in terms of operational exploitation of Doppler measurements including the capability to consistently perform multiple- Doppler wind synthesis in a fully operational framework. Using real and simulated Doppler observations, the authors show that the 3D wind fields retrieved in that framework can definitely be relied upon to achieve a consistent and detailed mapping of the airflow structure in various precipitation regimes despite radar baselines averaging _180 km and very limited scanning strategies. This achievement could be easily transposed to other operational networks and represents a remarkable opportunity to add further value to operational Doppler velocity measurements.

https://hal-meteofrance.archives-ouvertes.fr/meteo-00358754/document

Operational Multiple-Doppler Wind Retrieval Inferred from Long-Range Radial Velocity Measurements

The scanning Atmospheric Radiation Measurement (ARM) Program cloud radars (SACRs) are the primary instruments for documenting the four-dimensional structure and evolution of clouds within a 20–30-km radius of the ARM fixed and mobile sites. Here, the postprocessing of the calibrated SACR measurements is discussed. First, a feature mask algorithm that objectively determines the presence of significant radar returns is described. The feature mask algorithm is based on the statistical properties of radar receiver noise. It accounts for atmospheric emission and is applicable even for SACR profiles with few or no signal-free range gates. Using the nearest-in-time atmospheric sounding, the SACR radar reflectivities are corrected for gaseous attenuation (water vapor and oxygen) using a line-by-line absorption model. Despite having a high pulse repetition frequency, the SACR has a narrow Nyquist velocity limit and thus Doppler velocity folding is commonly observed. An unfolding algorithm that makes use of...

http://www.bnl.gov/envsci/pubs/pdf/2014/BNL-105484-2014-JA.pdf

Scanning ARM Cloud Radars. Part II: Data Quality Control and Processing

This paper presents the design and the test of an operational (staggered) triple-PRT (pulse repetition time) scheme that was implemented in July 2004 on the French operational C-band Trappes radar. The three interleaved pulse repetition frequencies (PRFs: PRF1, PRF2, and PRF3) that are used have the particularity to be very low and very close to each other (379, 325, and 303 Hz). The associated individual Nyquist velocities, VN1, VN2, and VN3, range between 4 and 5 m s−1 and the corresponding unambiguous distances are between 495 and 395 km. The ratios VN2/VN1 and VN3/VN1 are, respectively, equal to 6/7 and 4/5. The resulting extended Nyquist velocity is equal to 60 m s−1. One month of data (August 2004) representing more than 10 000 plan position indicators (PPIs) of clear-air, convective, and stratiform rain has been analyzed and histograms of errors have been computed. All histograms are symmetrical and show a well-defined peak centered on zero. The error distributions of the dual-PRT (V12, V1...

An Operational Triple-PRT Doppler Scheme for the French Radar Network

This paper describes the implementation of the staggered pulse repetition time (PRT) technique on NOAA's research and development WSR-88D in Norman, Oklahoma. The prototype algorithm incorporates a novel rule for the correct assignment of Doppler mean velocity that is needed to accommodate arbitrary stagger ratios. Description of the rule, consideration of errors, and choice of appropriate stagger ratios are presented. The staggered PRT algorithm is integrated with the standard processing on the WSR-88D, some details of which are included in the paper. A simple ground clutter canceller removes the pure complex time series mean (DC) component from autocovariance estimates; censoring of overlaid echoes and thresholding are equivalent to those used on the WSR-88D. Further, a cursory verification of statistical errors indicates good agreement with theoretical expectations. Although the staggered PRT algorithm operates in real time, it was advantageous to collect several events of staggered PRT time s...

Yannick F. Dubel

Papers

Design, Implementation, and Demonstration of a Staggered PRT Algorithm for the WSR-88D