Direction finding and likelihood ratio detection for oceanographic HF radars

Author Posting. © American Meteorological Society, 2022. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of the Atmospheric and Oceanic Technology 39(2), (2022): 223–235, https://doi.org/10.1175/JTECH-D-21-0110.1.Previous work with simulations of oceanographic high-frequency (HF) radars has identified possible improvements when using maximum likelihood estimation (MLE) for direction of arrival; however, methods for determining the number of emitters (here defined as spatially distinct patches of the ocean surface) have not realized these improvements. Here we describe and evaluate the use of the likelihood ratio (LR) for emitter detection, demonstrating its application to oceanographic HF radar data. The combined detection–estimation methods MLE-LR are compared with multiple signal classification method (MUSIC) and MUSIC parameters for SeaSonde HF radars, along with a method developed for 8-channel systems known as MUSIC-Highest. Results show that the use of MLE-LR produces similar accuracy, in terms of the RMS difference and correlation coefficients squared, as previous methods. We demonstrate that improved accuracy can be obtained for both methods, at the cost of fewer velocity observations and decreased spatial coverage. For SeaSondes, accuracy improvements are obtained with less commonly used parameter sets. The MLE-LR is shown to be able to resolve simultaneous closely spaced emitters, which has the potential to improve observations obtained by HF radars operating in complex current environments.This work was supported by the National Science Foundation (NSF) under Grant OCE-1658475. Computing resources were provided by the UCSB Center for Scientific Computing through an NSF MRSEC (DMR-1720256) and NSF CNS-1725797

High Frequency Radar Wind Turbine Interference Community Working Group Report

Land-based High Frequency (HF) Radars provide critically important observations of the coastal ocean that will be adversely affected by the spinning blades of utility-scale wind turbines. Pathways to mitigate the interference of turbines on HF radar observations exist for small number of turbines; however, a greatly increased pace of research is required to understand how to minimize the complex interference patterns that will be caused by the large arrays of turbines planned for the U.S. outer continental shelf. To support the U.S.’s operational and scientific needs, HF radars must be able to collect high-quality measurements of the ocean’s surface inand around areas with significant numbers of wind turbines. This is a solvable problem, but given the rapid pace of wind energy development, immediate action is needed to ensure that HF radar wind turbine interference mitigation efforts keep pace with the planned build out of turbines

Improving surface current resolution using direction finding algorithms for multiantenna high-frequency radars

Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of the Atmospheric and Oceanic Technology 36(10), (2019): 1997-2014, doi: 10.1175/JTECH-D-19-0029.1.While land-based high-frequency (HF) radars are the only instruments capable of resolving both the temporal and spatial variability of surface currents in the coastal ocean, recent high-resolution views suggest that the coastal ocean is more complex than presently deployed radar systems are able to reveal. This work uses a hybrid system, having elements of both phased arrays and direction finding radars, to improve the azimuthal resolution of HF radars. Data from two radars deployed along the U.S. East Coast and configured as 8-antenna grid arrays were used to evaluate potential direction finding and signal, or emitter, detection methods. Direction finding methods such as maximum likelihood estimation generally performed better than the well-known multiple signal classification (MUSIC) method given identical emitter detection methods. However, accurately estimating the number of emitters present in HF radar observations is a challenge. As MUSIC’s direction-of-arrival (DOA) function permits simple empirical tests that dramatically aid the detection process, MUSIC was found to be the superior method in this study. The 8-antenna arrays were able to provide more accurate estimates of MUSIC’s noise subspace than typical 3-antenna systems, eliminating the need for a series of empirical parameters to control MUSIC’s performance. Code developed for this research has been made available in an online repository.This analysis was supported by NSF Grants OCE-1657896 and OCE-1736930 to Kirincich, OCE-1658475 to Emery and Washburn and OCE-1736709 to Flament. Flament is also supported by NOAA’s Integrated Ocean Observing System through Award NA11NOS0120039. The authors thank Lindsey Benjamin, Alma Castillo, Ken Constantine, Benedicte Dousset, Ian Fernandez, Mael Flament, Dave Harris, Garrett Hebert, Ben Hodges, Victoria Futch, Matt Guanci, and Philip Moravcik for assistance in building, deploying, and operating the radars.2020-04-1

Evaluating Connectivity between Marine Protected Areas Using CODAR High-Frequency Radar

To investigate the connectivity between central California marine protected areas (MPAs), back-projections were calculated using the network of high-frequency (HF) radar ocean surface current mapping stations operated along the California coast by the member institutions of the Coastal Ocean Currents Monitoring Program with funding provided by California voters through Propositions 40 & 50 and administered by the State Coastal Conservancy. Trajectories of 1 km resolution grids of water particles were back-projected from ten MPAs each hour, out through 40 days in the past, from each day in 2008, producing a map of where surface waters travel over a 40-day period to reach the MPAs - and visualizations of the length of time the waters travel along these paths. By comparing the travel times of those back-projected track-points that crossed between MPA regions, the connection time between MPAs along the State\u27s central coast was assessed. Repeating these calculations resulted in a connectivity matrix between the MPAs in the region, and may be useful for assessing connectivity for the important invertebrate and fish larvae that are restricted to the surface ocean during a fraction of their lifecycle

Long-term morphological and hormonal follow-up in a single unit on 115 patients with adrenal incidentalomas

We investigated the natural course of adrenal incidentalomas in 115 patients by means of a long-term endocrine and morphological (CT) follow-up protocol (median 4 year, range 1–7 year). At entry, we observed 61 subclinical hormonal alterations in 43 patients (mainly concerning the ACTH–cortisol axis), but confirmatory tests always excluded specific endocrine diseases. In all cases radiologic signs of benignity were present. Mean values of the hormones examined at last follow-up did not differ from those recorded at entry. However in individual patients several variations were observed. In particular, 57 endocrine alterations found in 43 patients (37.2%) were no longer confirmed at follow-up, while 35 new alterations in 31 patients (26.9%) appeared de novo. Only four alterations in three patients (2.6%) persisted. Confirmatory tests were always negative for specific endocrine diseases. No variation in mean mass size was found between values at entry (25.4±0.9 mm) and at follow-up (25.7±0.9 mm), although in 32 patients (27.8%) mass size actually increased, while in 24 patients (20.8%) it decreased. In no case were the variations in mass dimension associated with the appearance of radiological criteria of malignancy. Kaplan–Meier curves indicated that the cumulative risk for mass enlargement (65%) and for developing endocrine abnormalities (57%) over time was progressive up to 80 months and independent of haemodynamic and humoral basal characteristics. In conclusion, mass enlargement and the presence or occurrence over time of subclinical endocrine alterations are frequent and not correlated, can appear at any time, are not associated with any basal predictor and, finally, are not necessarily indicative of malignant transformation or of progression toward overt disease

Delayed upwelling alters nearshore coastal ocean ecosystems in the northern California current

Wind-driven coastal ocean upwelling supplies nutrients to the euphotic zone near the coast. Nutrients fuel the growth of phytoplankton, the base of a very productive coastal marine ecosystem [Pauly D, Christensen V (1995) Nature 374:255–257]. Because nutrient supply and phytoplankton biomass in shelf waters are highly sensitive to variation in upwelling-driven circulation, shifts in the timing and strength of upwelling may alter basic nutrient and carbon fluxes through marine food webs. We show how a 1-month delay in the 2005 spring transition to upwelling-favorable wind stress in the northern California Current Large Marine Ecosystem resulted in numerous anomalies: warm water, low nutrient levels, low primary productivity, and an unprecedented low recruitment of rocky intertidal organisms. The delay was associated with 20- to 40-day wind oscillations accompanying a southward shift of the jet stream. Early in the upwelling season (May–July) off Oregon, the cumulative upwelling-favorable wind stress was the lowest in 20 years, nearshore surface waters averaged 2°C warmer than normal, surf-zone chlorophyll-a and nutrients were 50% and 30% less than normal, respectively, and densities of recruits of mussels and barnacles were reduced by 83% and 66%, respectively. Delayed early-season upwelling and stronger late-season upwelling are consistent with predictions of the influence of global warming on coastal upwelling regions.Keywords: coastal ocean upwelling, coastal marine ecosystems, marine ecology, climate variabilit

Role of metabolically active hormones in the insulin resistance associated with short-term glucocorticoid treatment

BACKGROUND: The mechanisms by which glucocorticoid therapy promotes obesity and insulin resistance are incompletely characterized. Modulations of the metabolically active hormones, tumour necrosis factor alpha (TNF alpha), ghrelin, leptin and adiponectin are all implicated in the development of these cardiovascular risk factors. Little is known about the effects of short-term glucocorticoid treatment on levels of these hormones. RESEARCH METHODS AND PROCEDURES: Using a blinded, placebo-controlled approach, we randomised 25 healthy men (mean (SD) age: 24.2 (5.4) years) to 5 days of treatment with either placebo or oral dexamethasone 3 mg twice daily. Fasting plasma TNFα, ghrelin, leptin and adiponectin were measured before and after treatment. RESULTS: Mean changes in all hormones were no different between treatment arms, despite dexamethasone-related increases in body weight, blood pressure, HDL cholesterol and insulin. Changes in calculated indices of insulin sensitivity (HOMA-S, insulin sensitivity index) were strongly related to dexamethasone treatment (p < 0.001). DISCUSSION: Our data do not support a role for TNF alpha, ghrelin, leptin or adiponectin in the insulin resistance associated with short-term glucocorticoid treatment

Planning for Change: Assessing the Potential Role of Marine Protected Areas and Fisheries Management Approaches for Resilience Management in a Changing Ocean

Despite progressive policies and continued advances in ocean management, numerous shifts associated with global changes have been observed in marine ecosystems in recent years, including warming, ocean acidification, and deoxygenation. As global change accelerates, science is needed to inform evidence-based management strategies for continued ecosystem services. Resilience management, in which actions are undertaken to promote the resistance and recovery responses of populations and ecosystems to disturbance, has been suggested as a possible strategy. However, empirical evidence for effective resilience management is still limited. To inform effective management strategies, mechanisms that underlie resilience to global change that can be influenced by management-ready actions must be identified and tested through observations, experiments, and modeling. Here, we discuss the potential links between three common management strategies (i.e., spatial restrictions such as marine protected areas, coordinated spatial protections, and fisheries management approaches) and potential mechanisms of resilience for marine populations and ecosystems, and provide guidance for future research on resilience management for a changing ocean drawing on insight gained by the Partnership for Interdisciplinary Studies of Coastal Oceans’ work at the science-policy interface in the California Current Large Marine Ecosystem