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The laser that's changing the world : the amazing stories behind lidar, from 3D mapping to self-driving cars
\"Tells the story of a laser technology that will have a big impact on society and the brilliant innovators responsible for its development\"-- Provided by publisher.
Book
Ground Penetrating Radar Theory and Applications
Ground-penetrating radar (GPR) is a rapidly developing field that has seen tremendous progress over the past 15 years. The development of GPR spans aspects of geophysical science, technology, and a wide range of scientific and engineering applications. The explosion of primary literature devoted to GPR technology, theory and applications has lead to a strong demand for an up-to-date synthesis and overview of this rapidly developing field. Because there are specifics in the utilization of GPR for different applications, a review of the current state of development of the applications along with the fundamental theory is required. This book will provide sufficient detail to allow both practitioners and newcomers to the area of GPR to use it as a handbook and primary research reference.
eBook
Current Status and Future Challenges of Weather Radar Polarimetry: Bridging the Gap between Radar Meteorology/Hydrology/Engineering and Numerical Weather Prediction
After decades of research and development, the WSR-88D (NEXRAD) network in the United States was upgraded with dual-polarization capability, providing polarimetric radar data (PRD) that have the potential to improve weather observations, quantification, forecasting, and warnings. The weather radar networks in China and other countries are also being upgraded with dual-polarization capability. Now, with radar polarimetry technology having matured, and PRD available both nationally and globally, it is important to understand the current status and future challenges and opportunities. The potential impact of PRD has been limited by their oftentimes subjective and empirical use. More importantly, the community has not begun to regularly derive from PRD the state parameters, such as water mixing ratios and number concentrations, used in numerical weather prediction (NWP) models.
In this review, we summarize the current status of weather radar polarimetry, discuss the issues and limitations of PRD usage, and explore potential approaches to more efficiently use PRD for quantitative precipitation estimation and forecasting based on statistical retrieval with physical constraints where prior information is used and observation error is included. This approach aligns the observation-based retrievals favored by the radar meteorology community with the model-based analysis of the NWP community. We also examine the challenges and opportunities of polarimetric phased array radar research and development for future weather observation.
Journal Article
Towards the Next Generation Operational Meteorological Radar
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 developing methods to compensate for polarimetric variable estimate biases introduced by electronic beam-steering. A research-to-operations (R2O) strategy for the PAR alternative for the WSR-88D replacement network is presented.
Journal Article
L‐Band InSAR Snow Water Equivalent Retrieval Uncertainty Increases With Forest Cover Fraction
There is a pressing need for global monitoring of snow water equivalent (SWE) at high spatiotemporal resolution, and L‐band (1–2 GHz) interferometric synthetic aperture radar (InSAR) holds promise. However, the technique has not seen extensive evaluation in forests. We evaluated this technique across varying forest canopy conditions using eight InSAR pairs collected at the Fraser Experimental Forest, Colorado, USA by NASA UAVSAR during the 10‐week NASA SnowEx 2021 Campaign. Compared with in situ measurements, we found root mean squared errors (RMSEs) of 14–17 mm for SWE changes in forest cover fractions (FCF) < 0.40, but RMSEs increased to 33–40 mm at FCF > 0.50. Statistical distributions between normalized lidar snow depths and normalized UAVSAR SWE were similar at FCF < 0.5, but diverged at FCF > 0.50. Thus, the upcoming NISAR L‐band satellite has strong potential for global snowpack monitoring, including below sparse to moderate forest cover. Plain Language Summary Monitoring the amount of water stored in seasonal snowpacks is essential for water resource management, but it remains challenging, particularly in mountain and forest environments. Satellite radar techniques may provide a viable path forward for snowpack monitoring, particularly at longer radar wavelengths (>20 cm) such as the radar used for the upcoming NASA‐ISRO SAR satellite mission. At these longer wavelengths, the radar signal can penetrate forest canopy, but the canopy interferes with the signal and may reduce the accuracy of the radar snowpack measurement. We examined the influence of forest cover on airborne radar measurements of the snowpack in the Fraser Experimental Forest, Colorado, USA and observed errors that increased with greater forest cover. Notably, the radar measurements were accurate for sparse to moderately dense forest covers. The radar snowpack measurements reproduced elevational trends observed in lidar‐measured snow depths, but we identified snowpack measurement errors that correlated with oblique radar viewing geometries. Considering these limitations, we conclude that the NASA‐ISRO SAR satellite mission represents a promising path toward global snowpack monitoring. Key Points We evaluated L‐band interferometry for snowpack monitoring in a montane forest in Colorado Retrievals of changes in snow water equivalent from L‐band interferometry were accurate and unbiased in forest cover fractions <0.40 Despite limitations, L‐band interferometry represents a promising path toward global snowpack monitoring
Journal Article
Strain Partitioning in the Southeastern Tibetan Plateau From Kinematic Modeling of High‐Resolution Sentinel‐1 InSAR and GNSS
Fault slip rates estimated from geodetic data are being integrated into seismic hazard models. The standard approach requires modeling velocities and relative (micro‐)plate motions, which is challenging for fault‐based models. We present a new approach to directly invert strain rates to solve for slip rates and distributed strain simultaneously. We generate velocity and strain rate fields over the southeastern Tibetan Plateau, utilizing Sentinel‐1 Interferometric Synthetic Aperture Radar data spanning 2014–2023. We derive slip rates using block modeling and by inverting strain rates. Our results show a partitioning between localized strain on faults and distributed deformation. The direct inversion of strain rates matches the geodetic data best when incorporating distributed moment sources, accounting for a similar proportion to on‐fault sources. The direct strain methodology also aligns best with the independent geological slip rates, especially near fault tips. As high‐resolution strain rate fields become increasingly available, we recommend direct inversion as the preferred practice. Plain Language Summary We focus on understanding earthquake potential in the southeastern Tibetan Plateau by measuring how and how fast the crust deforms. By analyzing 9 years of satellite radar images, we estimate how fast faults are slipping, which is crucial for assessing the hazard of future earthquakes. We tested two methods and found that the method directly incorporating measurements of surface strain rates provides more accurate results when compared to field‐based geologic slip rates. We show that the total deformation field is roughly equally split between energy accumulation on mapped active faults and distributed deformation away from the faults. The large amount of diffuse strain is an important constraint for rates of background seismicity. We discuss the limitations of various techniques used in modeling Earth's interseismic deformation and suggest prioritizing the direct strain methodology. Key Points We construct velocity and strain rate fields covering 1.3 million km2 of SE Tibet from Sentinel‐1 Interferometric Synthetic Aperture Radar Deformation is partitioned approximately equally between focused strain on the main mapped faults and diffuse deformation Direct inversion of strain rates removes the requirement to define artificial “blocks” and gives a better match to geological slip rates
Journal Article