Detecting Atlantic MOC Changes in an Ensemble of Climate Change Simulations

2007 ◽  
Vol 20 (8) ◽  
pp. 1571-1582 ◽  
Author(s):  
S. S. Drijfhout ◽  
W. Hazeleger
Keyword(s):  
Error Detection ◽  
Continuous Monitoring ◽  
Signal To Noise Ratio ◽  
Linear Trend ◽  
Maximum Amplitude ◽  
Internal Variability ◽  
Meridional Overturning Circulation ◽  
Detection Methods ◽  
Signal To Noise ◽  
Ensemble Mean

Abstract Signal-to-noise patterns for the meridional overturning circulation (MOC) have been calculated for an ensemble of greenhouse scenario runs. The greenhouse-forced signal has been defined as the linear trend in ensemble-mean MOC, after year 2000. It consists of an overall decrease and shoaling of the MOC, with maximum amplitudes of 10 Sv (Sv ≡ 106 m3 s−1) per century. In each member the internal variability is defined as the anomaly with respect to the ensemble-mean signal. The interannual variability of the MOC is dominated by a monopole with a maximum amplitude of 2 Sv at 40°N. This variability appears to be driven by the North Atlantic Oscillation (NAO), mainly through NAO-induced variations in the wind field. The signal-to-noise ratio was estimated for various time spans, all starting in 1950 or later. Different noise estimates were made, both with and without intra-annual variability, relevant for episodic and continuous monitoring, respectively, and with and without an estimate of the observational error. Detection of a greenhouse-forced MOC signal on the basis of episodic measurements is impossible before 2055. With continuous monitoring, detection becomes possible after 35 years of observation. The main motivation for calculating signal-to-noise ratios and detection times is their usefulness for local monitoring strategies and detection methods. The two-dimensional pattern of detection times of a MOC change supports the rationale for deploying a sustained monitoring array on at 26°N.

Weak Transient Electromagnetic Radiation Signal Detection Method Considering the New Watershed Image Segmentation Algorithm

2019 ◽  
Vol 34 (03) ◽  
pp. 2054009
Author(s):  
Wenjun Huo ◽  
Peng Chu ◽  
Kai Wang ◽  
Liangting Fu ◽  
Zhigang Niu ◽  
...  
Keyword(s):  
Electromagnetic Radiation ◽  
Cross Correlation ◽  
Detection Efficiency ◽  
Signal To Noise Ratio ◽  
Estimation Method ◽  
Detection Methods ◽  
Signal To Noise ◽  
Long Distance ◽  
Transient Electromagnetic ◽  
Noise Ratio

In order to study the detection methods of weak transient electromagnetic radiation signals, a detection algorithm integrating generalized cross-correlation and chaotic sequence prediction is proposed in this paper. Based on the dual-antenna test and cross-correlation information estimation method, the detection of aperiodic weak discharge signals under low signal-to-noise ratio is transformed into the estimation of periodic delay parameters, and the noise is reduced at the same time. The feasibility of this method is verified by simulation and experimental analysis. The results show that under the condition of low signal-to-noise ratio, the integrated method can effectively suppress the influence of 10 noise disturbances. It has a high detection probability for weak transient electromagnetic radiation signals, and needs fewer pulse accumulation times, which improves the detection efficiency and is more suitable for long-distance detection of weak electromagnetic radiation sources.

scholarly journals Emerging New Climate Extremes Over Europe

2021 ◽  
Author(s):  
Albert Ossó ◽  
Richard P. Allan ◽  
Ed Hawkins ◽  
Len Shaffrey ◽  
Douglas Maraun
Keyword(s):  
Signal To Noise Ratio ◽  
Climate Extremes ◽  
Internal Variability ◽  
Winter Precipitation ◽  
Climate Indices ◽  
Human Society ◽  
Signal To Noise ◽  
Climate Signal ◽  
Local Climate ◽  
Noise Ratio

Abstract Human society and natural systems are intrinsically adapted to the local climate mean and variability. Therefore, changes relative to the local expected variability are highly relevant for assessing impact and planning for adaptation as the climate changes. We analyse the emerging climate signal relative to the diagnosed internal variability (signal-to-noise ratio, S/N) of a set of recently published climate indices over Europe. We calculate the signal-to-noise ratio with respect to a recent baseline (1951-1983) which relates to recent societal experience. In this framework, we find that during the 2000-2016 period, many areas of Europe already experienced significant changes in climate extremes, even when compared to this recent period which is within living memory. In particular, the S/N of extreme temperatures is larger than 1 and 2 over 34% and 4% of Europe, respectively. We also find that about 15% of Europe is experiencing more intense winter precipitation events, while in summer, 7% of Europe is experiencing stronger drought-inducing conditions.

scholarly journals Emerging new climate extremes over Europe

2021 ◽  
Author(s):  
Albert Ossó ◽  
Richard P. Allan ◽  
Ed Hawkins ◽  
Len Shaffrey ◽  
Douglas Maraun
Keyword(s):  
Signal To Noise Ratio ◽  
Climate Extremes ◽  
Internal Variability ◽  
Winter Precipitation ◽  
Climate Indices ◽  
Human Society ◽  
Signal To Noise ◽  
Climate Signal ◽  
Local Climate ◽  
Noise Ratio

AbstractHuman society and natural systems are intrinsically adapted to the local climate mean and variability. Therefore, changes relative to the local expected variability are highly relevant for assessing impact and planning for adaptation as the climate changes. We analyse the emerging climate signal relative to the diagnosed internal variability (signal-to-noise ratio, S/N) of a set of recently published climate indices over Europe. We calculate the signal-to-noise ratio with respect to a recent baseline (1951–1983) which relates to recent societal experience. In this framework, we find that during the 2000–2016 period, many areas of Europe already experienced significant changes in climate extremes, even when compared to this recent period which is within living memory. In particular, the S/N of extreme temperatures is larger than 1 and 2 over 34% and 4% of Europe, respectively. We also find that about 15% of Europe is experiencing more intense winter precipitation events, while in summer, 7% of Europe is experiencing stronger drought-inducing conditions.

scholarly journals Atmospherically Forced Regional Ocean Simulations of the South China Sea: Scale Dependency of the Signal-to-Noise Ratio

2020 ◽  
Vol 50 (1) ◽  
pp. 133-144
Author(s):  
Shengquan Tang ◽  
Hans von Storch ◽  
Xueen Chen
Keyword(s):  
Initial Conditions ◽  
Signal To Noise Ratio ◽  
Internal Variability ◽  
Scale Dependency ◽  
External Forcing ◽  
Signal To Noise ◽  
Ocean Models ◽  
Noise Ratio ◽  
Ensemble Of Simulations ◽  
Oceanic Model

AbstractWhen subjecting ocean models to atmospheric forcing, the models exhibits two types of variability—a response to the external forcing (hereafter referred to as signal) and inherently generated (internal, intrinsic, unprovoked, chaotic) variations (hereafter referred to as noise). Based on an ensemble of simulations with an identical atmospherically forced oceanic model that differ only in the initial conditions at different times, the signal-to-noise ratio of the atmospherically forced oceanic model is determined. In the large scales, the variability of the model output is mainly induced by the external forcing and the proportion of the internal variability is small, so the signal-to-noise ratio is large. For smaller scales, the influence of the external forcing weakens and the influence of the internal variability strengthens, so the signal-to-noise ratio becomes less and less. Thus, the external forcing is dominant for large scales, while most of the variability is internally generated for small scales.

Blinking Detection Methods for Loran-C

1994 ◽  
Vol 47 (1) ◽  
pp. 46-53
Author(s):  
André Nieuwland
Keyword(s):  
Signal To Noise Ratio ◽  
Detection Methods ◽  
Signal To Noise ◽  
Safe Operation ◽  
Preliminary Version ◽  
Noise Ratio ◽  
Wild Goose

To ensure integrity of the Loran-C radionavigation system during non-precision approaches, an automatic blinking system notifies the user when the system is not functioning within specifications. To be certain that timely detection of this blinking can be guaranteed, one of the requirements imposed on an airborne Loran-C receiver is that it should flag an alert when the signal to noise ratio drops below –6 . This paper addresses some blinking detection methods, that will ensure safe operation beyond this –6 dB limit. A preliminary version of this article was presented at the Wild Goose Conference in Birmingham, August 1992.

scholarly journals Comparing the Accuracy of Visual and Computerized Onset Detection Methods on Simulated Electromyography Signals with Varying Signal-to-Noise Ratios

2021 ◽  
Vol 6 (3) ◽  
pp. 70
Author(s):  
Erik Kowalski ◽  
Danilo S. Catelli ◽  
Mario Lamontagne
Keyword(s):  
Visual Inspection ◽  
Visual Detection ◽  
Signal To Noise Ratio ◽  
Detection Methods ◽  
Onset Detection ◽  
Signal To Noise ◽  
Quality Signals ◽  
Electromyography Signals ◽  
Double Threshold ◽  
Better Than

Electromyography (EMG) onsets determined by computerized detection methods have been compared against the onsets selected by experts through visual inspection. However, with this type of approach, the true onset remains unknown, making it impossible to determine if computerized detection methods are better than visual detection (VD) as they can only be as good as what the experts select. The use of simulated signals allows for all aspects of the signal to be precisely controlled, including the onset and the signal-to-noise ratio (SNR). This study compared three onset detection methods: approximated generalized likelihood ratio, double threshold (DT), and VD determined by eight trained individuals. The selected onset was compared against the true onset in simulated signals which varied in the SNR from 5 to 40 dB. For signals with 5 dB SNR, the VD method was significantly better, but for SNRs of 20 dB or greater, no differences existed between the VD and DT methods. The DT method is recommended as it can improve objectivity and reduce time of analysis when determining EMG onsets. Even for the best-quality signals (SNR of 40 dB), all the detection methods were off by 15–30 ms from the true onset and became progressively more inaccurate as the SNR decreased. Therefore, although all the detection methods provided similar results, they can be off by 50–80 ms from the true onset as the SNR decreases to 10 dB. Caution must be used when interpreting EMG onsets, especially on signals where the SNR is low or not reported at all.

A Bispectral Analysis of the Radio Emissions of Pulsar J0437-4715

2020 ◽  
Vol 09 (04) ◽  
pp. 2050018
Author(s):  
Alexander Faustmann ◽  
Jacki Gilmore ◽  
Vereese van Tonder ◽  
Maciej Serylak
Keyword(s):  
Signal To Noise Ratio ◽  
Gaussian Model ◽  
Higher Order ◽  
Detection Methods ◽  
High Signal ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Alternative Detection ◽  
Higher Order Spectra

A combination of the very low signal-to-noise ratio and the very large parameter space spanned by pulsar emissions makes pulsar detection a challenging task. Currently, brute force parameter searches are often used for pulsar detection and a cyclostationary Gaussian model is assumed for pulsar emissions. Higher-Order spectra offer high signal-to-noise ratio domains in problems where the desired signal is polluted by Gaussian noise. The presence of nonzero higher-order spectral components in pulsar bursts may offer alternative detection methods. This work presents a review of higher-order statistics and offers a motivation for their use in the characterization of pulsar bursts. A dish from the MeerKAT telescope was used to acquire recorded radio bursts from pulsar J0437-4715. These bursts were found to contain nonzero bispectral components that were dispersed in the same way as the components of the power spectrum.

A Detection Method for Overlapped Spikes

2011 ◽  
Vol 267 ◽  
pp. 530-535
Author(s):  
Jia Qi ◽  
Min Dai ◽  
Gang Zheng ◽  
Tong Tong Liu
Keyword(s):  
Detection Method ◽  
Signal To Noise Ratio ◽  
False Negative ◽  
False Negative Rate ◽  
Energy Operator ◽  
Detection Methods ◽  
Signal To Noise ◽  
Threshold Detection ◽  
Noise Ratio ◽  
Nonlinear Energy

A new spike detection method is proposed in order to detect the overlapped spikes. In order to avoid missing overlapped spikes, the method adds threshold detection based on window detection method. Moreover, nonlinear energy operator is introduced to make the method strong even under low signal-to-noise ratio situation. In addition, the method solves the repeated detection problem by estimating slopes. Experiments show that the method is good for any occasion whatever the low signal-to-noise ratio or baseline wander. Especially for the overlapped spikes detection, it has much lower false-negative-rate than other traditional detection methods.

scholarly journals All-nanofiber–based, ultrasensitive, gas-permeable mechanoacoustic sensors for continuous long-term heart monitoring

2020 ◽  
Vol 117 (13) ◽  
pp. 7063-7070 ◽  
Author(s):  
Md Osman Goni Nayeem ◽  
Sunghoon Lee ◽  
Hanbit Jin ◽  
Naoji Matsuhisa ◽  
Hiroaki Jinno ◽  
...  
Keyword(s):  
Continuous Monitoring ◽  
Signal To Noise Ratio ◽  
Low Frequency ◽  
High Sensitivity ◽  
Frequency Region ◽  
Sound Waves ◽  
Signal To Noise ◽  
Low Intensity ◽  
Heart Monitoring

The prolonged and continuous monitoring of mechanoacoustic heart signals is essential for the early diagnosis of cardiovascular diseases. These bodily acoustics have low intensity and low frequency, and measuring them continuously for long periods requires ultrasensitive, lightweight, gas-permeable mechanoacoustic sensors. Here, we present an all-nanofiber mechanoacoustic sensor, which exhibits a sensitivity as high as 10,050.6 mV Pa−1 in the low-frequency region (<500 Hz). The high sensitivity is achieved by the use of durable and ultrathin (2.5 µm) nanofiber electrode layers enabling a large vibration of the sensor during the application of sound waves. The sensor is ultralightweight, and the overall weight is as small as 5 mg or less. The devices are mechanically robust against bending, and show no degradation in performance even after 1,000-cycle bending. Finally, we demonstrate a continuous long-term (10 h) measurement of heart signals with a signal-to-noise ratio as high as 40.9 decibels (dB).

Research of edge detection methods in the task of pattern recognition on images with low contrast

2021 ◽  
Vol 1 ◽  
pp. 123-128
Author(s):  
E.V. Belyaeva ◽  
Keyword(s):  
Pattern Recognition ◽  
Edge Detection ◽  
Signal To Noise Ratio ◽  
Similarity Index ◽  
Structural Similarity ◽  
Detection Methods ◽  
Signal To Noise ◽  
Structural Similarity Index ◽  
Low Contrast ◽  
Gaussian Filters

The article discusses edge detection methods separately and combinations of edge detection filters with antialiasing filters in the task of pattern recognition on images with low contrast. Sobel, Canny, Otsu and thresholding filters are considered as edge detection methods. Median and Gaussian filters are considered as smoothing filters. The performance of the filters is assessed using the peak signal-to-noise ratio (PSNR) and the structural similarity index (SSIM).

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