An official website of the United States government
Abstract This study focuses on the application of phased array radars (PARs) to observe tornadoes and their formation. PAR technology for meteorological applications is maturing and may become a valuable tool for the meteorological community. A fully digital PAR offers a range of benefits including adaptive scanning techniques, higher temporal resolution especially via radar imaging modes, and denser vertical sampling to allow for more complete observations of severe hazard structure and evolution. To best understand the benefits of such a system, synthetic PAR observations are generated from archived mobile rapid-scan observations collected by the Rapid X-band Polarimetric radar (RaXPol) to emulate typical operational radar ranges and PAR-enabled scanning strategy effects. In this study, a synthetic PAR data tool is applied to two tornadic cases (24 May 2011 El Reno, Oklahoma, tornado and the 24 May 2016 Dodge City, Kansas, tornadoes) and one non-tornadic case (17 April 2013). Results indicate that, despite increasing standoff ranges and using vertical imaging, a PAR can still observe a similar mode of tornadogenesis (i.e., non-descending TVS) as traditional mobile systems but with a slight delay in observing intensification at increasing standoff ranges and reduced change in measured intensity. The PAR-enabled vertical imaging mode does not eliminate our ability to identify the TVS at different spoiling factors, but changes to the structure of the TVS may have operational implications. We hope that the improved understanding of meteorological benefits from these synthetic PAR data can provide useful insight for fully digital PAR radar placement and warning operations.
more »
« less
A Framework for Comparisons of Downburst Precursor Observations Using an All-Digital Phased-Array Weather Radar
Abstract Downbursts are rapidly evolving meteorological phenomena with numerous vertically oriented precursor signatures, and the temporal resolution and vertical sampling of the current NEXRAD system are too coarse to observe their evolution and precursor signatures properly. A future all-digital polarimetric phased-array weather radar (PAR) should be able to improve both temporal resolution and spatial sampling of the atmosphere to provide better observations of rapidly evolving hazards such as downbursts. Previous work has been focused on understanding the trade-offs associated with using various scanning techniques on stationary PARs; however, a rotating, polarimetric PAR (RPAR) is a more feasible and cost-effective candidate. Thus, understanding the trade-offs associated with using various scanning techniques on an RPAR is vital in learning how to best observe downbursts with such a system. This work develops a framework for analyzing the trade-offs associated with different scanning strategies in the observation of downbursts and their precursor signatures. A proof-of-concept analysis—which uses a Cloud Model 1 (CM1)-simulated downburst-producing thunderstorm—is also performed with both conventional and imaging scanning strategies in an adaptive scanning framework to show the potential value and feasibility of the framework. Preliminary results from the proof-of-concept analysis indicate that there is indeed a limit to the benefits of imaging as an update time speedup method. As imaging is used to achieve larger speedup factors, corresponding data degradation begins to hinder the observations of various precursor signatures.
more »
« less
- Award ID(s):
- 2114817
- PAR ID:
- 10474369
- Publisher / Repository:
- AMS
- Date Published:
- Journal Name:
- Journal of Atmospheric and Oceanic Technology
- Volume:
- 40
- Issue:
- 8
- ISSN:
- 0739-0572
- Page Range / eLocation ID:
- 919 to 938
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Downbursts present a major operational forecasting challenge. Numerous radar-based signatures have been proposed for nowcasting downburst development, including recent research on polarimetric signatures associated with downbursts. However, the reliability of these signatures, and their relationship to downburst intensity, are not well established. In this work, we develop an idealized one-dimensional model of downburst development with bin microphysics and a coupled polarimetric radar forward operator to study the relationships, if any, between proposed downburst radar signatures (namely descending Z and Kdp cores) and forcing mechanisms (i.e., precipitation loading and diabatic cooling). The model is able to realistically reproduce observed downburst radar signatures and evolution, with precipitation loading being the dominant forcing mechanism close to the 0°C level and diabatic cooling becoming dominant closer to the surface. Environmental sensitivity runs show that for a given initial particle size distribution, the diabatic cooling forcing/downdraft magnitude and Kdp exhibit opposite responses to variations in temperature lapse rate and RH, while Z and total precipitation loading forcing are mostly insensitive to the environment. However, ensemble simulations show that although neither Z or Kdp are well-correlated with the instantaneous forcing magnitudes at most heights, Kdp below the 0°C level is well-correlated with the resultant downburst intensity at the surface within a given thermodynamic environment, with higher Kdp aloft corresponding to stronger downbursts. These findings support the use and further exploration of Kdp cores near the melting level as downburst radar precursors.more » « less
-
null (Ed.)Abstract As the existing NEXRAD network nears the end of its life cycle, intense study and planning are underway to design a viable replacement system. Ideally, such a system would offer improved temporal resolution compared to NEXRAD, without a loss in data quality. In this study, scan speedup techniques—such as beam multiplexing (BMX) and radar imaging—are tested to assess their viability in obtaining high-quality rapid updates for a simulated long-range weather radar. The results of this study—which uses a Weather Research and Forecasting (WRF) Model–simulated supercell case—show that BMX generally improves data quality for a given scan time or can provide a speedup factor of 1.69–2.85 compared to NEXRAD while maintaining the same level of data quality. Additionally, radar imaging is shown to improve data quality and/or decrease scan time when selectively used; however, deleterious effects are observed when imaging is used in regions with sharp reflectivity gradients parallel to the beam spoiling direction. Consideration must be given to the subsequent loss of sensitivity and beam broadening. Finally, imaging is shown to have an effect on the radar-derived mesocyclone strength (Δ V ) of a simulated supercell. Because BMX and radar imaging are most easily achieved with an all-digital phased array radar (PAR), these results make a strong argument for the use of all-digital PAR for high-resolution weather observations. It is believed that the results from this study can inform decisions about possible scanning strategies and design of a NEXRAD replacement system for high-resolution weather radar data.more » « less
-
Fluorescence imaging microscopy has traditionally been used because of the high specificity that is achievable through fluorescence labeling techniques and optical filtering. When combined with spectral imaging technologies, fluorescence microscopy can allow for quantitative identification of multiple fluorescent labels. We are working to develop a new approach for spectral imaging that samples the fluorescence excitation spectrum and may provide increased signal strength. The enhanced signal strength may be used to provide increased spectral sensitivity and spectral, spatial, and temporal sampling capabilities. A proof of concept excitation scanning system has shown over 10-fold increase in signal to noise ratio compared to emission scanning hyperspectral imaging. Traditional hyperspectral imaging fluorescence microscopy methods often require minutes of acquisition time. We are developing a new configuration that utilizes solid state LEDs to combine multiple illumination wavelengths in a 2-mirror assembly to overcome the temporal limitations of traditional hyperspectral imaging. We have previously reported on the theoretical performance of some of the aspects of this system by using optical ray trace modeling. Here, we present results from prototyping and benchtop testing of the system, including assembly, optical characterization, and data collection. This work required the assembly and characterization of a novel excitation scanning hyperspectral microscopy system, containing 12 LEDs ranging from 365- 425 nm, 12 lenses, a spherical mirror, and a flat mirror. This unique approach may reduce the long image acquisition times seen in traditional hyperspectral imaging while maintaining high specificity and sensitivity for multilabel identification and autofluorescence imaging in real time.more » « less
-
null (Ed.)The world faces an increasing need to phase out harmful chemicals and design sustainable alternatives across various consumer products and industrial applications. Alternatives assessment is an emerging field with focus on identifying viable solutions to substitute harmful chemicals. However, current methods fail to consider trade-offs from human and ecosystem exposures, and from impacts associated with chemical supply chains and product life cycles. To close this gap, we propose a life cycle based alternatives assessment (LCAA) framework for consistently integrating quantitative exposure and life cycle impact performance in the substitution process. We start with a pre-screening based on function-related decision rules, followed by three progressive tiers from (1) rapid risk screening of various alternatives for the consumer use stage, to (2) an assessment of chemical supply chain impacts for selected alternatives with substantially different synthesis routes, and (3) an assessment of product life cycle impacts for alternatives with substantially different product life cycles. Each tier focuses on relevant impacts and uses streamlined assessment methods. While the initial risk screening will be sufficient for evaluating chemicals with similar supply chains, each additional tier helps further restricting the number of viable solutions, while avoiding unacceptable trade-offs. We test our LCAA framework in a proof-of-concept case study for identifying suitable alternatives to a harmful plasticizer in household flooring. Results show that the use stage dominates human health impacts across alternatives, supporting that a rapid risk screening is sufficient unless very different supply chains or a broader set of alternative materials or technologies are considered. Combined with currently used indicators for technical and economic performance, our LCAA framework is suitable for informing function-based substitution at the level of chemicals, materials and product applications to foster green and sustainable chemistry solutions.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1175/JTECH-D-22-0130.1
