Generation of Low-Frequency Spiciness Variability in the Thermocline*

2011 ◽  
Vol 41 (2) ◽  
pp. 365-377 ◽  
Author(s):  
Thomas Kilpatrick ◽  
Niklas Schneider ◽  
Emanuele Di Lorenzo
Keyword(s):  
Markov Model ◽  
Large Scale ◽  
Spatial Scales ◽  
Low Frequency ◽  
Passive Tracer ◽  
Wind Stress Curl ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
Geostrophic Advection

Abstract The generation of variance by anomalous advection of a passive tracer in the thermocline is investigated using the example of density-compensated temperature and salinity anomalies, or spiciness. A coupled Markov model is developed in which wind stress curl forces the large-scale baroclinic ocean pressure that in turn controls the anomalous geostrophic advection of spiciness. The “double integration” of white noise atmospheric forcing by this Markov model results in a frequency (ω) spectrum of large-scale spiciness proportional to ω−4, so that spiciness variability is concentrated at low frequencies. An eddy-permitting regional model hindcast of the northeast Pacific (1950–2007) confirms that time series of large-scale spiciness variability are exceptionally smooth, with frequency spectra ∝ ω−4 for frequencies greater than 0.2 cpy. At shorter spatial scales (wavelengths less than ∼500 km), the spiciness frequency spectrum is whitened by mesoscale eddies, but this eddy-forced variability can be filtered out by spatially averaging. Large-scale and long-term measurements are needed to observe the variance of spiciness or any other passive tracer subject to anomalous advection in the thermocline.

scholarly journals Responses of Vertebrate Wildlife to Oil and Natural Gas Development: Patterns and Frontiers

2021 ◽  
Author(s):  
A. D. Chalfoun
Keyword(s):  
Natural Gas ◽  
Anthropogenic Activities ◽  
Spatial Scales ◽  
Habitat Type ◽  
Population Level ◽  
Low Frequencies ◽  
Natural Gas Development ◽  
The Usa ◽  
Oil And Natural Gas

Abstract Purpose of Review Anthropogenic activities can lead to the loss, fragmentation, and alteration of wildlife habitats. I reviewed the recent literature (2014–2019) focused on the responses of avian, mammalian, and herpetofaunal species to oil and natural gas development, a widespread and still-expanding land use worldwide. My primary goals were to identify any generalities in species’ responses to development and summarize remaining gaps in knowledge. To do so, I evaluated the directionality of a wide variety of responses in relation to taxon, location, development type, development metric, habitat type, and spatiotemporal aspects. Recent Findings Studies (n = 70) were restricted to the USA and Canada, and taxonomically biased towards birds and mammals. Longer studies, but not those incorporating multiple spatial scales, were more likely to detect significant responses. Negative responses of all types were present in relatively low frequencies across all taxa, locations, development types, and development metrics but were context-dependent. The directionality of responses by the same species often varied across studies or development metrics. Summary The state of knowledge about wildlife responses to oil and natural gas development has developed considerably, though many biases and gaps remain. Studies outside of North America and that focus on herpetofauna are lacking. Tests of mechanistic hypotheses for effects, long-term studies, assessment of response thresholds, and experimental designs that isolate the effects of different stimuli associated with development, remain critical. Moreover, tests of the efficacy of habitat mitigation efforts have been rare. Finally, investigations of the demographic effects of development across the full annual cycle were absent for non-game species and are critical for the estimation of population-level effects.

scholarly journals Variability of Cloudiness over Mountain Terrain in the Western United States

2017 ◽  
Vol 18 (5) ◽  
pp. 1227-1245 ◽  
Author(s):  
Edwin Sumargo ◽  
Daniel R. Cayan
Keyword(s):  
United States ◽  
Large Scale ◽  
Spatial Scales ◽  
High Elevation ◽  
Empirical Orthogonal Functions ◽  
Western United States ◽  
Spatial And Temporal Variability ◽  
Regional Patterns ◽  
Cloud Albedo

Abstract This study investigates the spatial and temporal variability of cloudiness across mountain zones in the western United States. Daily average cloud albedo is derived from a 19-yr series (1996–2014) of half-hourly Geostationary Operational Environmental Satellite (GOES) images. During springtime when incident radiation is active in driving snowmelt–runoff processes, the magnitude of daily cloud variations can exceed 50% of long-term averages. Even when aggregated over 3-month periods, cloud albedo varies by ±10% of long-term averages in many locations. Rotated empirical orthogonal functions (REOFs) of daily cloud albedo anomalies over high-elevation regions of the western conterminous United States identify distinct regional patterns, wherein the first five REOFs account for ~67% of the total variance. REOF1 is centered over Northern California and Oregon and is pronounced between November and March. REOF2 is centered over the interior northwest and is accentuated between March and July. Each of the REOF/rotated principal components (RPC) modes associates with anomalous large-scale atmospheric circulation patterns and one or more large-scale teleconnection indices (Arctic Oscillation, Niño-3.4, and Pacific–North American), which helps to explain why anomalous cloudiness patterns take on regional spatial scales and contain substantial variability over seasonal time scales.

scholarly journals Comments on “Reconstruction of the Extratropical NH Mean Temperature over the Last Millennium with a Method That Preserves Low-Frequency Variability”

2012 ◽  
Vol 25 (22) ◽  
pp. 7991-7997 ◽  
Author(s):  
Anders Moberg
Keyword(s):  
Large Scale ◽  
Low Frequency ◽  
Temperature Reconstruction ◽  
Noise Variance ◽  
Low Frequencies ◽  
Scale Temperature ◽  
Low Frequency Variability ◽  
High Frequency Variability ◽  
Frequency Temperature ◽  
Correct Estimate

Abstract Christiansen and Ljungqvist have presented an extratropical NH temperature reconstruction using a method (LOC) that they claim “preserves” low-frequency variability, at the expense of exaggerated high-frequency variability. Using theoretical arguments and a pseudoproxy experiment, it is demonstrated here that the LOC method is not guaranteed to preserve variability at any frequency. Rather, LOC reconstructions will have more variance than true large-scale temperature averages at all frequencies. This variance inflation, however, can be negligible at those frequencies where the noise variance in individual proxies is small enough to be effectively cancelled when computing an average over the available proxies. Because the proxy noise variance at low frequencies cannot be directly estimated, and thus has to be regarded as unknown, it is safer to regard a reconstruction with the LOC method as providing an estimate of the upper bound of the large-scale low-frequency temperature variability rather than one with a correct estimate of this variance.

Inadequate Standards Currently Applied by Local Authorities to Determine Statutory Nuisance from LF and Infrasound

2003 ◽  
Vol 22 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Hazel Guest
Keyword(s):  
Local Authority ◽  
Low Frequency ◽  
Measurement Information ◽  
Frequency Noise ◽  
Local Authorities ◽  
Low Frequencies ◽  
Specific Effects ◽  
Basic Understanding

Knowledge of the latest results in Low Frequency Noise (LFN) and infrasound research are not being transmitted, either to government whose job it is to legislate on standards of noise and vibration, or to local authority officers whose job it is to look into complaints and enforce standards. The dismissal of complaints is frequently based on inappropriate techniques such as the application of A-weighting, a lack of understanding of vibration transmission including building resonance, and a lack of basic understanding about the perception of low frequencies by complainants, for instance the lowering of the lower audibility threshold arising from exposure. This paper asks those involved in research to ensure that their relevant findings are more widely disseminated, along with advice to legislators and local authorities on measurement, information on LF and infrasound resonance in buildings, recommendations for appropriate standards to be used in assessing LF and infrasound as a Statutory Nuisance, and information about the effects of long-term exposure. There is a need for more research in situ into specific effects.

scholarly journals SUSTAINABLE AGRICULTURE MANAGEMENTS TO CONTROL SOIL EROSION

2021 ◽  
Author(s):  
Artemi Cerdà ◽  
Enric Terol
Keyword(s):  
Soil Erosion ◽  
Sustainable Agriculture ◽  
Spatial Scales ◽  
Low Frequency ◽  
Traditional Management ◽  
Erosion Rates ◽  
Olive Groves ◽  
Simulated Rain ◽  
The Impact

High rates of soil erosion compromise sustainable agriculture. In rainfed agricultural fields, erosion rates several orders ofmagnitude higher than the erosion rates considered tolerable have been quantified. In Mediterranean rainfed crops suchas vineyards, almonds and olive groves, and in the new sloping citrus and persimmon plantations, the rates of soil lossmake it necessary to apply measures to reduce them to avoid collapse in agricultural production. Managements such asweeds, catch crops and mulches (straw and pruning remains) are viable options to achieve sustainability. This work appliesmeasurements through plots, simulated rainfall experiments and ISUM (Improved Stock-Unearhing method) to quantifythe loss of soil at different temporal and spatial scales in fields of traditional management (herbicide or tillage) and underalternative management (mulches and plant covers). The work carried out at the experimental station for the study of soilerosion in the Sierra de Enguera and those of Montesa and Les Alcusses provide information on erosion plots undernatural rain. Experiments carried out with simulated rain in fields of olive, almond, citrus, persimmon, vineyard and fruittrees report the hydrological and erosive response under low frequency and high intensity rains. And finally, the ISUMtopographic method report the impact of long-term management, from the plantation. The results indicate that the loss ofsoil is greater (x10-1000) in soils under traditional management (tillage and herbicide) due to the fact that they remain barefor most of the year. The use of straw mulch immediately reduces soil erosion by two orders of magnitude. Also mulchesfrom chipped pruned branches remains are very efficient but require more years to reduce soil loss. Weeds and catchcrops are very efficient in controlling erosion.

Interdisciplinary data-constrained 3-D potential field modelling with IGMAS+

2021 ◽  
Author(s):  
Denis Anikiev ◽  
Hans-Jürgen Götze ◽  
Judith Bott ◽  
Angela Maria Gómez-García ◽  
Maria Laura Gomez Dacal ◽  
...  
Keyword(s):  
Large Scale ◽  
Spatial Scales ◽  
Geophysical Methods ◽  
Receiver Functions ◽  
Research Centre ◽  
Small Scale ◽  
Gravity And Magnetic ◽  
Structural Density ◽  
Scale Models

<p>We introduce a modelling concept for the construction of 3-D data-constrained subsurface structural density models at different spatial scales: from large-scale models (thousands of square km) to regional (hundreds of square km) and small-scale (tens of square km) models used in applied geophysics. These models are important for understanding the drivers of geohazards, for efficient and sustainable extraction of resources from sedimentary basins such as groundwater, hydrocarbons or deep geothermal energy, as well as for investigation of capabilities of long-term underground storage of gas and radioactive materials.</p><p>The modelling concept involves interactive fitting of potential fields (gravity and magnetics) and their derivatives within IGMAS+ (Interactive Gravity and Magnetic Application System), a well-known software tool with almost 40 years of development behind it. The core of IGMAS+ is the analytical solution of the volume integral for gravity and magnetic effects of homogeneous bodies, bounded by polyhedrons of triangulated model interfaces. The backbone model is constrained by interdisciplinary data, e.g. geological maps, seismic reflection and refraction profiles, structural signatures obtained from seismic receiver functions, local surveys etc. The software supports spherical geometries to resolve the first-order effects related to the curvature of the Earth, which is especially important for large-scale models.</p><p>Currently being developed and maintained at the Helmholtz Centre Potsdam – GFZ German Research Centre, IGMAS+ has a cross-platform implementation with parallelization of computations and optimized storage. The powerful graphical interface makes the interactive modelling and geometry modification process user-friendly and robust. Historically IGMAS+ is free for research and education purposes and has a long-term plan to remain so.</p><p>IGMAS+ has been used in various tectonic settings and we demonstrate its flexibility and usability on several lithospheric-scale case studies in South America and Europe.</p><p>Both science and industry are close to the goal of treating all available geoscientific data and geophysical methods inside a single subsurface model that aims to integrate most of the interdisciplinary measurement-based constraints and essential structural trends coming from geology. This approach presents challenges for both its implementation within the modelling software and the usability and plausibility of generated results, requiring a modelling concept that integrates the data methods in a feasible way together with recent advances in data science methods. As such, we present the future outlook of our modelling concept in regards to these challenges.</p>

New Results of the Baikal Experiment on Forecasting Effect of Macroscopic Nonlocal Correlations

2019 ◽  
pp. 56-72
Author(s):  
S.M Korotaev ◽  
N.M. Budnev ◽  
V.O. Serdyuk ◽  
Ye.O. Kiktenko ◽  
D.A. Orekhova
Keyword(s):  
Solar Activity ◽  
Active Layer ◽  
Large Scale ◽  
Forecast Accuracy ◽  
Random Component ◽  
Low Frequencies ◽  
Nonlocal Correlations ◽  
Sea Current ◽  
Local Impacts

The long-term deep-sea experiment on study of macroscopic quantum nonlocal correlations of natural large-scale random dissipative processes has been conducted in Lake Baikal since 2012. Correlations of the probe processes in detectors insulated from classical local impacts, between each other and with the large-scale source-processes are studied. These correlations are observed at extremely low frequencies and characterized by the large time shifts. The most important feature of random process nonlocal correlations is presence of a considerable advanced component in them. The dominant source is solar activity. At the same time, the correlations with macroturbulence in the Baikal active layer are revealed. The advanced nonlocal correlations can be applied to forecast the processes with big random component. A forecast series of macroturbulence sea current velocity variations in the active layer, which demonstrated forecast accuracy of the order of tenths of cm/s at an advance of the order of month, has been obtained by the latest experimental data. The possibility of using nonlocal correlations to forecast solar activity in advance of the order of the year has also been demonstrated.

Frequency spectrum analysis of plant storage tissue during deterioration

1977 ◽  
Vol 55 (18) ◽  
pp. 2437-2438 ◽  
Author(s):  
Terry A. Tattar ◽  
David M. Sylvia
Keyword(s):  
Low Frequency ◽  
Soft Rot ◽  
Healthy Plant ◽  
Storage Tissue ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
Pass Filter ◽  
Pass Through ◽  
High Pass ◽  
Plant Storage

Frequency spectra of healthy plant storage tissue indicate that the tissue acts as a high-pass filter that attenuates low frequencies and allows high frequencies to pass through. During progressive deterioration of the tissue from infection of soft-rot bacteria, the frequency spectra indicated a loss in ability of the tissues to filter low frequency signals.

scholarly journals Spectra of Low-Frequency Ground Vibrations Generated by High-Speed Trains on Layered Ground

1997 ◽  
Vol 16 (4) ◽  
pp. 257-270 ◽  
Author(s):  
V.V. Krylov
Keyword(s):  
High Speed ◽  
Low Frequency ◽  
Ground Vibration ◽  
Ground Vibrations ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
High Speed Trains ◽  
Frequency Components ◽  
Noticeable Reduction ◽  
Layered Ground

Increase in speeds of modern railway trains is usually accompanied by higher levels of generated ground vibrations. In the author's earlier paper [V.V. Krylov, Applied Acoustics, 44, 149–164 (1995)], it has been shown that especially large increase in vibration level may occur if train speeds v exceed the velocity of Rayleigh surface waves in the ground cR., i.e., v > cR. Such a situation might arise, for example, with French TGV trains for which speeds over 515 km/h have been achieved. The present paper investigates the effect of geological layered structure of the ground on ground vibrations generated by high-speed trains. It is shown that, since Rayleigh wave velocities in layered ground are dispersive and normally increase at lower frequencies associated with deeper penetration of surface wave energy into the ground, the trans-Rayleigh condition v > cR may not hold at very low frequencies. This will cause a noticeable reduction in low-frequency components of generated ground vibration spectra. Theoretical results are illustrated by numerically calculated frequency spectra of ground vibrations generated by single axle loads travelling at different speeds and by TGV or Eurostar high-speed trains.

scholarly journals Intrinsic Variability of Sea Level from Global Ocean Simulations: Spatiotemporal Scales

2015 ◽  
Vol 28 (10) ◽  
pp. 4279-4292 ◽  
Author(s):  
Guillaume Sérazin ◽  
Thierry Penduff ◽  
Sandy Grégorio ◽  
Bernard Barnier ◽  
Jean-Marc Molines ◽  
...  
Keyword(s):  
Sea Level ◽  
Time Scales ◽  
General Circulation ◽  
Spatial Scales ◽  
Full Range ◽  
Low Frequency ◽  
Global Ocean ◽  
Small Scale ◽  
Atmospheric Variability ◽  
Low Frequencies

Abstract In high-resolution ocean general circulation models (OGCMs), as in process-oriented models, a substantial amount of interannual to decadal variability is generated spontaneously by oceanic nonlinearities: that is, without any variability in the atmospheric forcing at these time scales. The authors investigate the temporal and spatial scales at which this intrinsic oceanic variability has the strongest imprints on sea level anomalies (SLAs) using a ° global OGCM, by comparing a “hindcast” driven by the full range of atmospheric time scales with its counterpart forced by a repeated climatological atmospheric seasonal cycle. Outputs from both simulations are compared within distinct frequency–wavenumber bins. The fully forced hindcast is shown to reproduce the observed distribution and magnitude of low-frequency SLA variability very accurately. The small-scale (L < 6°) SLA variance is, at all time scales, barely sensitive to atmospheric variability and is almost entirely of intrinsic origin. The high-frequency (mesoscale) part and the low-frequency part of this small-scale variability have almost identical geographical distributions, supporting the hypothesis of a nonlinear temporal inverse cascade spontaneously transferring kinetic energy from high to low frequencies. The large-scale (L > 12°) low-frequency variability is mostly related to the atmospheric variability over most of the global ocean, but it is shown to remain largely intrinsic in three eddy-active regions: the Gulf Stream, Kuroshio, and Antarctic Circumpolar Current (ACC). Compared to its ¼° predecessor, the authors’ ° OGCM is shown to yield a stronger intrinsic SLA variability, at both mesoscale and low frequencies.

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