Статті в журналах з теми "Threshold exceedance"
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1
Flunker, John C., Christopher Zuidema, Jihoon Jung, Edward Kasner, Martin Cohen, Edmund Seto, Elena Austin, and June T. Spector. "Potential Impacts of Different Occupational Outdoor Heat Exposure Thresholds among Washington State Crop and Construction Workers and Implications for Other Jurisdictions." International Journal of Environmental Research and Public Health 19, no. 18 (September 14, 2022): 11583. http://dx.doi.org/10.3390/ijerph191811583.
Анотація:
Occupational heat exposure is associated with substantial morbidity and mortality among outdoor workers. We sought to descriptively evaluate spatiotemporal variability in heat threshold exceedances and describe potential impacts of these exposures for crop and construction workers. We also present general considerations for approaching heat policy-relevant analyses. We analyzed county-level 2011–2020 monthly employment (Bureau of Labor Statistics Quarterly Census of Employment and Wages) and environmental exposure (Parameter-elevation Relationships on Independent Slopes Model (PRISM)) data for Washington State (WA), USA, crop (North American Industry Classification System (NAICS) 111 and 1151) and construction (NAICS 23) sectors. Days exceeding maximum daily temperature thresholds, averaged per county, were linked with employment estimates to generate employment days of exceedances. We found spatiotemporal variability in WA temperature threshold exceedances and crop and construction employment. Maximum temperature exceedances peaked in July and August and were most numerous in Central WA counties. Counties with high employment and/or high numbers of threshold exceedance days, led by Yakima and King Counties, experienced the greatest total employment days of exceedances. Crop employment contributed to the largest proportion of total state-wide employment days of exceedances with Central WA counties experiencing the greatest potential workforce burden of exposure. Considerations from this analysis can help inform decision-making regarding thresholds, timing of provisions for heat rules, and tailoring of best practices in different industries and areas.
2
GREENWOOD, PRISCILLA E., and PETR LANSKY. "INFORMATION CONTENT IN THRESHOLD DATA WITH NON-GAUSSIAN NOISE." Fluctuation and Noise Letters 07, no. 01 (March 2007): L79—L89. http://dx.doi.org/10.1142/s0219477507003702.
Анотація:
If data is binary, it is probable that the combination of a signal of interest plus a noise has been simplified by a thresholding mechanism, as in, e.g., a neuron firing mechanism. For identifying optimal signal or coding range of binary data, Fisher information is an attractive measure. A general formula allows the signal level or signal range producing the most information-rich data to be identified if the noise distribution is known. In this paper we study the information content of binary data resulting from threshold exceedance of a signal plus an arbitrary type of noise. For a specified parametric family of distributions a fixed proportion of exceedances is optimal for any combination of signal, threshold, and noise amplitude. If the ratio of noise to signal level is constant, Fisher information is unimodal for many noise distributions. The results extend to the case of a random signal and to inter-exceedance-interval data. The family of gamma noise distributions is used for illustration.
3
Zhang, Sen, Gaetano Pecoraro, Qigang Jiang, and Michele Calvello. "Definition of Rainfall Thresholds for Landslides Using Unbalanced Datasets: Two Case Studies in Shaanxi Province, China." Water 15, no. 6 (March 10, 2023): 1058. http://dx.doi.org/10.3390/w15061058.
Анотація:
The Lueyang and Xunyang counties in the Shaanxi province (China) are highly susceptible to rainfall-induced landslides. Rainfall thresholds are the most used tool to predict the occurrence of rainfall-induced landslides over large areas. However, the definition of robust thresholds may be difficult for unbalanced datasets, for which the number of non-landslide observations is much higher than the number of landslide observations. This study aims at defining adequate rainfall thresholds for the two study areas using landslide datasets that are strongly unbalanced in terms of occurrences vs. non-occurrences. Two types of rainfall thresholds are determined using a frequentist method at several non-exceedance and exceedance probabilities, separately considering rainfall events responsible for landslides (positive thresholds) and rainfall events not responsible for landslides (negative thresholds). The comparison between the two sets of thresholds shows that the method based on non-triggering events allows defining rainfall thresholds characterized by lower uncertainties and a better performance than the ones defined considering the triggering events, in both the study areas. In particular, the best-performing thresholds are the negative threshold defined at 15% exceedance probability for the Lueyang county and the negative threshold defined at 20% exceedance probability for the Xunyang county.
4
Deidda, R. "A multiple threshold method for fitting the generalized Pareto distribution and a simple representation of the rainfall process." Hydrology and Earth System Sciences Discussions 7, no. 4 (July 23, 2010): 4957–94. http://dx.doi.org/10.5194/hessd-7-4957-2010.
Анотація:
Abstract. Previous studies indicate the generalized Pareto distribution (GPD) as a suitable distribution function to reliably describe the exceedances of daily rainfall records above a proper optimum threshold, which should be selected as small as possible to retain the largest sample while assuring an acceptable fitting. Such an optimum threshold may differ from site to site, affecting consequently not only the GPD scale parameter, but also the probability of threshold exceedance. Thus a first objective of this paper is to derive some expressions to parameterize a simple threshold-invariant three-parameter distribution function which is able to describe zero and non zero values of rainfall time series by assuring a perfect overlapping with the GPD fitted on the exceedances of any threshold larger than the optimum one. Since the proposed distribution does not depend on the local thresholds adopted for fitting the GPD, it will only reflect the on-site climatic signature and thus appears particularly suitable for hydrological applications and regional analyses. A second objective is to develop and test the Multiple Threshold Method (MTM) to infer the parameters of interest on the exceedances of a wide range of thresholds using again the concept of parameters threshold-invariance. We show the ability of the MTM in fitting historical daily rainfall time series recorded with different resolutions. Finally, we prove the supremacy of the MTM fit against the standard single threshold fit, often adopted for partial duration series, by evaluating and comparing the performances on Monte Carlo samples drawn by GPDs with different shape and scale parameters and different discretizations.
5
Deidda, R. "A multiple threshold method for fitting the generalized Pareto distribution to rainfall time series." Hydrology and Earth System Sciences 14, no. 12 (December 14, 2010): 2559–75. http://dx.doi.org/10.5194/hess-14-2559-2010.
Анотація:
Abstract. Previous studies indicate the generalized Pareto distribution (GPD) as a suitable distribution function to reliably describe the exceedances of daily rainfall records above a proper optimum threshold, which should be selected as small as possible to retain the largest sample while assuring an acceptable fitting. Such an optimum threshold may differ from site to site, affecting consequently not only the GPD scale parameter, but also the probability of threshold exceedance. Thus a first objective of this paper is to derive some expressions to parameterize a simple threshold-invariant three-parameter distribution function which assures a perfect overlapping with the GPD fitted on the exceedances over any threshold larger than the optimum one. Since the proposed distribution does not depend on the local thresholds adopted for fitting the GPD, it is expected to reflect the on-site climatic signature and thus appears particularly suitable for hydrological applications and regional analyses. A second objective is to develop and test the Multiple Threshold Method (MTM) to infer the parameters of interest by using exceedances over a wide range of thresholds applying again the concept of parameters threshold-invariance. We show the ability of the MTM in fitting historical daily rainfall time series recorded with different resolutions and with a significative percentage of heavily quantized data. Finally, we prove the supremacy of the MTM fit against the standard single threshold fit, often adopted for partial duration series, by evaluating and comparing the performances on Monte Carlo samples drawn by GPDs with different shape and scale parameters and different discretizations.
6
Roy, Ritu, Dewan Mohammad Enamul Haque, Shamima Ferdousi Sifa, Sumya Tasnim, Tonoy Mahmud, and Tanzim Hayat. "Empirical Approach Based Rainfall Threshold Estimation for Landslide Occurrence in Cox's Bazar District, Bangladesh." Dhaka University Journal of Earth and Environmental Sciences 11, no. 1 (February 1, 2023): 81–94. http://dx.doi.org/10.3329/dujees.v11i1.63713.
Анотація:
Rainfall threshold estimation empirically to forecast rainfall-induced landslide events provides crucial information to reduce landslide impact. The landslide events triggered by rainfall are common in Cox's Bazar district, especially during the monsoon season. Geological settings and climatic conditions make this area more landslide-prone leading to huge losses of lives and property. Establishing an effective early warning system based on a rainfall threshold value has become a top priority to save people's lives, the economy, and the environment. We have employed three empirical approaches to estimate rainfall thresholds. Intensity-Duration, Event-Duration, and Antecedent Rainfall thresholds are the most conventional rainfall methods to identify the lowest amount of rainfall that triggers landslide. The Intensity-Duration (ID) and Event-Duration (ED) rainfall threshold equations are calculated using a simple power-law curve. For 5% exceedance probability level ID defined as: T5: I = 3.63 D-0.1313 & ED as T5: E = 3.63 D0.8687. Similarly, for 1% exceedance probability level ID defined as: T1: I= 2.78 D-0.1313 & T1: E = 2.78 D0.8687 for ED. Both 1% and 5% rainfall threshold equations are the minimum rainfall threshold equations. Since the 5% exceedance probability threshold line delineates the lower end of all the observed data points for landslide events, it is considered the minimum threshold line for Cox's Bazar. According to the 5% exceedance probability level threshold equation, mean intensity of 2.39 mmh-1 or 57.4 mm cumulated rainfall in 24 hours is required to initiate a landslide event. Whereas, for longer duration events such as 120h, rainfall intensity of 1.93 mmh-1 or continuous rainfall of 232 mm appears to be sufficient in landslide initiation. There is a less than 5% chance of a landslide below this threshold limit. In the context of 3-day and 5-day antecedent rainfall thresholds, we found that a minimum of 130 mm in 72 h (3-day) and 210 mm in 120 h (5-day) could initiate a landslide event. We have compared our thresholds with a few global and local rainfall threshold estimates. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 11(1), 2022: 81-94
7
Schönenberg-Tu, Anna-Li, Dirk Cysarz, Benjamin Petzold, Carl Benjamin Blümel, Christa Raak, Oliver Fricke, Friedrich Edelhäuser, and Wolfram Scharbrodt. "Pressure Time Dose as a Representation of Intracranial Pressure Burden and Its Dependency on Intracranial Pressure Waveform Morphology at Different Time Intervals." Sensors 23, no. 19 (September 24, 2023): 8051. http://dx.doi.org/10.3390/s23198051.
Анотація:
Intracranial pressure (ICP) burden or pressure time dose (PTD) is a valuable clinical indicator for pending intracranial hypertension, mostly based on threshold exceedance. Pulse frequency and waveform morphology (WFM) of the ICP signal contribute to PTD. The temporal resolution of the ICP signal has a great influence on PTD calculation but has not been systematically studied yet. Hence, the temporal resolution of the ICP signal on PTD calculation is investigated. We retrospectively analysed continuous 48 h ICP recordings with high temporal resolution obtained from 94 patients at the intensive care unit who underwent neurosurgery due to an intracranial haemorrhage and received an intracranial pressure probe (43 females, median age: 72 years, range: 23 to 88 years). The cumulative area under the curve above the threshold of 20 mmHg was compared for different temporal resolutions of the ICP signal (beat-to-beat, 1 s, 300 s, 1800 s, 3600 s). Events with prolonged ICP elevation were compared to those with few isolated threshold exceedances. PTD increased for lower temporal resolutions independent of WFM and frequency of threshold exceedance. PTDbeat-to-beat best reflected the impact of frequency of threshold exceedance and WFM. Events that could be distinguished in PTDbeat-to-beat became magnified more than 7-fold in PTD1s and more than 104 times in PTD1h, indicating an overestimation of PTD. PTD calculation should be standardised, and beat-by-beat PTD could serve as an easy-to-grasp indicator for the impact of frequency and WFM of ICP elevations on ICP burden.
8
Aranda, Diana, Jose V. Lopez, Helena M. Solo-Gabriele, and Jay M. Fleisher. "Using probabilities of enterococci exceedance and logistic regression to evaluate long term weekly beach monitoring data." Journal of Water and Health 14, no. 1 (September 14, 2015): 81–89. http://dx.doi.org/10.2166/wh.2015.030.
Анотація:
Recreational water quality surveillance involves comparing bacterial levels to set threshold values to determine beach closure. Bacterial levels can be predicted through models which are traditionally based upon multiple linear regression. The objective of this study was to evaluate exceedance probabilities, as opposed to bacterial levels, as an alternate method to express beach risk. Data were incorporated into a logistic regression for the purpose of identifying environmental parameters most closely correlated with exceedance probabilities. The analysis was based on 7,422 historical sample data points from the years 2000–2010 for 15 South Florida beach sample sites. Probability analyses showed which beaches in the dataset were most susceptible to exceedances. No yearly trends were observed nor were any relationships apparent with monthly rainfall or hurricanes. Results from logistic regression analyses found that among the environmental parameters evaluated, tide was most closely associated with exceedances, with exceedances 2.475 times more likely to occur at high tide compared to low tide. The logistic regression methodology proved useful for predicting future exceedances at a beach location in terms of probability and modeling water quality environmental parameters with dependence on a binary response. This methodology can be used by beach managers for allocating resources when sampling more than one beach.
9
Engler, C., W. Birmili, G. Spindler та A. Wiedensohler. "Analysis of exceedances in the daily PM<sub>10</sub> mass concentration (50 μg m<sup>−3</sup>) at a roadside station in Leipzig, Germany". Atmospheric Chemistry and Physics 12, № 21 (5 листопада 2012): 10107–23. http://dx.doi.org/10.5194/acp-12-10107-2012.
Анотація:
Abstract. Five years of PM10 and PM2.5 ambient air measurements at a roadside, an urban, and a regional background site in Leipzig (Germany) were analyzed for violations of the legal PM10 limit value (EC, 1999). The annual mean PM10 concentrations at the three sites were well below the legal threshold of 40 μg m−3 (32.6, 22.0 and 21.7 μg m−3, respectively). At roadside, the daily maximum value of 50 μg m−3 was exceeded on 232 days (13% of all days) in 2005–2009, which led to a violation of the EC directive in three out of five years. We analysed the meteorological factors and local source contributions that eventually led to the exceedances of the daily limit value. As noted in other urban environments before, most exceedance days were observed in the cold season. Exceedance days were most probable under synoptic situations characterised by stagnant winds, low temperatures and strong temperature inversions in winter time. However, these extreme situations accounted for only less than half of the exeedance days. We also noticed a significant number of exceedance days that occurred in the cold season under south-westerly winds, and in the warm season in the presence of easterly winds. Our analysis suggests that local as well as regional sources of PM are equally responsible for exceedances days at the roadside site. The conclusion is that a combined effort of local, national and international reduction measures appears most likely to avoid systematic exceedances of the daily limit value in the future.
10
Kang, Daiwen, Rohit Mathur, Kenneth Schere, Shaocai Yu, and Brian Eder. "New Categorical Metrics for Air Quality Model Evaluation." Journal of Applied Meteorology and Climatology 46, no. 4 (April 1, 2007): 549–55. http://dx.doi.org/10.1175/jam2479.1.
Анотація:
Abstract Traditional categorical metrics used in model evaluations are “clear cut” measures in that the model’s ability to predict an “exceedance” is defined by a fixed threshold concentration and the metrics are defined by observation–forecast sets that are paired both in space and time. These metrics are informative but limited in evaluating the performance of air quality forecast (AQF) systems because AQF generally examines exceedances on a regional scale rather than a single monitor. New categorical metrics—the weighted success index (WSI), area hit (aH), and area false-alarm ratio (aFAR)—are developed. In the calculation of WSI, credits are given to the observation–forecast pairs within the observed exceedance region (missed forecast) or the forecast exceedance region (false alarm), depending on the distance of the points from the central line (perfect observation–forecast match line or 1:1 line on scatterplot). The aH and aFAR are defined by matching observed and forecast exceedances within an area (i.e., model grid cells) surrounding the observation location. The concept of aH and aFAR resembles the manner in which forecasts are usually issued. In practice, a warning is issued for a region of interest, such as a metropolitan area, if an exceedance is forecast to occur anywhere within the region. The application of these new categorical metrics, which are supplemental to the traditional counterparts (critical success index, hit rate, and false-alarm ratio), to the Eta Model–Community Multiscale Air Quality (CMAQ) forecast system has demonstrated further insight into evaluating the forecasting capability of the system (e.g., the new metrics can provide information about how the AQF system captures the spatial variations of pollutant concentrations).
11
Madrid, A. E., J. M. Angulo, and J. Mateu. "Spatial threshold exceedance analysis through marked point processes." Environmetrics 23, no. 1 (December 19, 2011): 108–18. http://dx.doi.org/10.1002/env.1141.
12
Mason, Simon J., Jacqueline S. Galpin, Lisa Goddard, Nicholas E. Graham, and Balakanapathy Rajartnam. "Conditional Exceedance Probabilities." Monthly Weather Review 135, no. 2 (February 1, 2007): 363–72. http://dx.doi.org/10.1175/mwr3284.1.
Анотація:
Abstract Probabilistic forecasts of variables measured on a categorical or ordinal scale, such as precipitation occurrence or temperatures exceeding a threshold, are typically verified by comparing the relative frequency with which the target event occurs given different levels of forecast confidence. The degree to which this conditional (on the forecast probability) relative frequency of an event corresponds with the actual forecast probabilities is known as reliability, or calibration. Forecast reliability for binary variables can be measured using the Murphy decomposition of the (half) Brier score, and can be presented graphically using reliability and attributes diagrams. For forecasts of variables on continuous scales, however, an alternative measure of reliability is required. The binned probability histogram and the reliability component of the continuous ranked probability score have been proposed as appropriate verification procedures in this context, but are subject to some limitations. A procedure is proposed that is applicable in the context of forecast ensembles and is an extension of the binned probability histogram. Individual ensemble members are treated as estimates of quantiles of the forecast distribution, and the conditional probability that the observed precipitation, for example, exceeds the amount forecast [the conditional exceedance probability (CEP)] is calculated. Generalized linear regression is used to estimate these conditional probabilities. A diagram showing the CEPs for ranked ensemble members is suggested as a useful method for indicating reliability when forecasts are on a continuous scale, and various statistical tests are suggested for quantifying the reliability.
13
Draghicescu, Dana, and Rosaria Ignaccolo. "Modeling threshold exceedance probabilities of spatially correlated time series." Electronic Journal of Statistics 3 (2009): 149–64. http://dx.doi.org/10.1214/08-ejs252.
14
Engler, C., W. Birmili, G. Spindler та A. Wiedensohler. "Analysis of exceedances in the daily PM<sub>10</sub> mass concentration (50 μg m<sup>−3</sup>) at a roadside station in Leipzig, Germany". Atmospheric Chemistry and Physics Discussions 11, № 5 (25 травня 2011): 15831–73. http://dx.doi.org/10.5194/acpd-11-15831-2011.
Анотація:
Abstract. Five years of PM10 and PM2.5 ambient air measurements at a roadside, an urban, and a regional background site in Leipzig (Germany) were analyzed for violations of the legal PM10 limit value (1999/30/EC, 1999). The annual mean PM10 concentrations at the three sites were well below the legal threshold of 40 μg m−3 (32.6, 22.0 and 21.7 μg m−3, respectively). However, at the roadside site, the daily maximum value of 50 μg m−3 was exceeded on 232 days (13 % of all days) in 2005–2009, which corresponds to 57 days more than warranted by the EC directive. We analysed the meteorological and local source factors that eventually led to these surplus exceedences. Not surprisingly, the highest pollutant concentrations and most exceedance days were observed in winter. Average concentrations for exceedance and non exceedance days of 64 and 28 μg m−3 at roadside and 40 and 19 μg m−3 in the regional background were observed, suggesting urban contributions of 24 and 8 μg m−3, respectively. Statistical and back trajectory cluster analysis yielded the essential result that PM10 concentrations were regionally enhanced during high pressure conditions, characterized by very low temperature, dry air masses, very low wind speeds, and stable stratification. The latter factor was instrumental in generating high PM10 concentrations at roadside as well as in the regional background through pollution trapping below the atmospheric inversion. During winter exceedance days, the highest organic and elemental carbon mass concentrations were measured. The fewest exceedance days were observed during fast moving air masses from the west, characterized by slightly unstable stratification and lower air pressure. During wintrily exceedance days, about half of PM10 at roadside was originating from regional transport and half from the urban-related sources. This result indicates that both are equally important in generating exceedance days in case of favourable meteorological conditions and cannot be separately considered. Our conclusion is that a combined effort of local, national and international reduction measures could most likely avoid systematic exceedances of the daily limit value in the future.
15
Peel, Syd, and Laurence J. Wilson. "A Diagnostic Verification of the Precipitation Forecasts Produced by the Canadian Ensemble Prediction System." Weather and Forecasting 23, no. 4 (August 1, 2008): 596–616. http://dx.doi.org/10.1175/2008waf2006099.1.
Анотація:
Abstract A comparatively long period of relative stability in the evolution of the Canadian Ensemble Forecast System was exploited to compile a large homogeneous set of precipitation forecasts. The probability of exceedance of a given threshold was computed as the fraction of ensemble member forecasts surpassing that threshold, and verified directly against observations from 36 stations across the country. These forecasts were stratified into warm and cool seasons and assessed against the observations through attributes diagrams, Brier skill scores, and areas under receiver operating characteristic curves. These measures were deemed sufficient to illuminate the salient features of a forecast system. Particular attention was paid to forecasts of 24-h accumulation, especially the exceedance of thresholds in the upper decile of station climates. The ability of the system to forecast extended dry periods was also explored. Warm season forecasts for the 90th percentile threshold were found to be competitive with, even superior to, those for the cool season when verifying across the sample lumping together all of the stations. The relative skill of the forecasts in the two seasons depends strongly on station location, however. Moreover, the skill of the warm season forecasts rapidly drops below cool season values as the thresholds become more extreme. The verification, particularly of the cool season, is sensitive to the calibration of the gauge reports, which is complicated by the inclusion of snow events in the observational record.
16
Herman, Gregory R., and Russ S. Schumacher. "Extreme Precipitation in Models: An Evaluation." Weather and Forecasting 31, no. 6 (November 21, 2016): 1853–79. http://dx.doi.org/10.1175/waf-d-16-0093.1.
Анотація:
Abstract A continental United States (CONUS)-wide framework for analyzing quantitative precipitation forecasts (QPFs) from NWP models from the perspective of precipitation return period (RP) exceedances is introduced using threshold estimates derived from a combination of NOAA Atlas 14 and older sources. Forecasts between 2009 and 2015 from several different NWP models of varying configurations and spatial resolutions are analyzed to assess bias characteristics and forecast skill for predicting RP exceedances. Specifically, NOAA’s Global Ensemble Forecast System Reforecast (GEFS/R) and the National Severe Storms Laboratory WRF (NSSL-WRF) model are evaluated for 24-h precipitation accumulations. The climatology of extreme precipitation events for 6-h accumulations is also explored in three convection-allowing models: 1) NSSL-WRF, 2) the North American Mesoscale 4-km nest (NAM-NEST), and 3) the experimental High Resolution Rapid Refresh (HRRR). The GEFS/R and NSSL-WRF are both found to exhibit similar 24-h accumulation RP exceedance climatologies over the U.S. West Coast to those found in observations and are found to be approximately equally skillful at predicting these exceedance events in this region. In contrast, over the eastern two-thirds of the CONUS, GEFS/R struggles to predict the predominantly convectively driven extreme QPFs, predicting far fewer events than are observed and exhibiting inferior forecast skill to the NSSL-WRF. The NSSL-WRF and HRRR are found to produce 6-h extreme precipitation climatologies that are approximately in accord with those found in the observations, while NAM-NEST produces many more RP exceedances than are observed across all of the CONUS.
17
Li, Yunyao, Daniel Tong, Siqi Ma, Saulo R. Freitas, Ravan Ahmadov, Mikhail Sofiev, Xiaoyang Zhang, et al. "Impacts of estimated plume rise on PM2.5 exceedance prediction during extreme wildfire events: a comparison of three schemes (Briggs, Freitas, and Sofiev)." Atmospheric Chemistry and Physics 23, no. 5 (March 9, 2023): 3083–101. http://dx.doi.org/10.5194/acp-23-3083-2023.
Анотація:
Abstract. Plume height plays a vital role in wildfire smoke dispersion and the subsequent effects on air quality and human health. In this study, we assess the impact of different plume rise schemes on predicting the dispersion of wildfire air pollution and the exceedances of the National Ambient Air Quality Standards (NAAQS) for fine particulate matter (PM2.5) during the 2020 western United States wildfire season. Three widely used plume rise schemes (Briggs, 1969; Freitas et al., 2007; Sofiev et al., 2012) are compared within the Community Multiscale Air Quality (CMAQ) modeling framework. The plume heights simulated by these schemes are comparable to the aerosol height observed by the Multi-angle Imaging SpectroRadiometer (MISR) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). The performance of the simulations with these schemes varies by fire case and weather conditions. On average, simulations with higher plume injection heights predict lower aerosol optical depth (AOD) and surface PM2.5 concentrations near the source region but higher AOD and PM2.5 in downwind regions due to the faster spread of the smoke plume once ejected. The 2-month mean AOD difference caused by different plume rise schemes is approximately 20 %–30 % near the source regions and 5 %–10 % in the downwind regions. Thick smoke blocks sunlight and suppresses photochemical reactions in areas with high AOD. The surface PM2.5 difference reaches 70 % on the West Coast of the USA, and the difference is lower than 15 % in the downwind regions. Moreover, the plume injection height affects pollution exceedance (>35 µg m−3) predictions. Higher plume heights generally produce larger downwind PM2.5 exceedance areas. The PM2.5 exceedance areas predicted by the three schemes largely overlap, suggesting that all schemes perform similarly during large wildfire events when the predicted concentrations are well above the exceedance threshold. At the edges of the smoke plumes, however, there are noticeable differences in the PM2.5 concentration and predicted PM2.5 exceedance region. For the whole period of study, the difference in the total number of exceedance days could be as large as 20 d in northern California and 4 d in the downwind regions. This disagreement among the PM2.5 exceedance forecasts may affect key decision-making regarding early warning of extreme air pollution episodes at local levels during large wildfire events.
18
Cheetham, Michael. "Nonsynchronous, episodic incision: Floodplain sensitivity, threshold exceedance and complex response." Quaternary International 279-280 (November 2012): 86. http://dx.doi.org/10.1016/j.quaint.2012.07.378.
19
Zhang, Xuebin, Gabriele Hegerl, Francis W. Zwiers, and Jesse Kenyon. "Avoiding Inhomogeneity in Percentile-Based Indices of Temperature Extremes." Journal of Climate 18, no. 11 (June 1, 2005): 1641–51. http://dx.doi.org/10.1175/jcli3366.1.
Анотація:
Abstract Using a Monte Carlo simulation, it is demonstrated that percentile-based temperature indices computed for climate change detection and monitoring may contain artificial discontinuities at the beginning and end of the period that is used for calculating the percentiles (base period). This would make these exceedance frequency time series unsuitable for monitoring and detecting climate change. The problem occurs because the threshold calculated in the base period is affected by sampling error. On average, this error leads to overestimated exceedance rates outside the base period. A bootstrap resampling procedure is proposed to estimate exceedance frequencies during the base period. The procedure effectively removes the inhomogeneity.
20
Trojanowski, Jacek. "Theory of the detection function for migration-based methods for the detection of microseismic events." GEOPHYSICS 83, no. 6 (November 1, 2018): A87—A91. http://dx.doi.org/10.1190/geo2018-0237.1.
Анотація:
A detection function is used during the migration-based detection of microseismic events. A potential event is detected when a detection function exceeds some specified threshold value. However, the value of this threshold is usually selected manually; therefore, the detection process is subjective and lacks constraints on the probability of exceeding the threshold. In practice, any change in the detection algorithm results in a change in the distribution of the detection-function values. Consequently, the threshold value must be adjusted to have the same probability of exceedance as before. I have developed a general probabilistic theory of the detection function that is valid for any migration-based detection method. For the sake of transparency and the interchangeability of the results, I recommend the definition of a threshold in terms of the exceedance probability. To do so, it is necessary to define a probability distribution of the detection function. I have also developed a general method for assessing the detectability of a given stacking method for the purpose of comparing different migration-based methods. A simple synthetic example indicates how to use the developed theory in practice.
21
Hofer, Christoph, and Andreas Papritz. "Predicting Threshold Exceedance by Local Block Means in Soil Pollution Surveys." Mathematical Geosciences 42, no. 6 (June 18, 2010): 631–56. http://dx.doi.org/10.1007/s11004-010-9287-4.
22
Meyer, N. K., A. V. Dyrrdal, R. Frauenfelder, B. Etzelmüller, and F. Nadim. "Hydrometeorological threshold conditions for debris flow initiation in Norway." Natural Hazards and Earth System Sciences 12, no. 10 (October 11, 2012): 3059–73. http://dx.doi.org/10.5194/nhess-12-3059-2012.
Анотація:
Abstract. Debris flows, triggered by extreme precipitation events and rapid snow melt, cause considerable damage to the Norwegian infrastructure every year. To define intensity-duration (ID) thresholds for debris flow initiation critical water supply conditions arising from intensive rainfall or snow melt were assessed on the basis of daily hydro-meteorological information for 502 documented debris flow events. Two threshold types were computed: one based on absolute ID relationships and one using ID relationships normalized by the local precipitation day normal (PDN). For each threshold type, minimum, medium and maximum threshold values were defined by fitting power law curves along the 10th, 50th and 90th percentiles of the data population. Depending on the duration of the event, the absolute threshold intensities needed for debris flow initiation vary between 15 and 107 mm day−1. Since the PDN changes locally, the normalized thresholds show spatial variations. Depending on location, duration and threshold level, the normalized threshold intensities vary between 6 and 250 mm day−1. The thresholds obtained were used for a frequency analysis of over-threshold events giving an estimation of the exceedance probability and thus potential for debris flow events in different parts of Norway. The absolute thresholds are most often exceeded along the west coast, while the normalized thresholds are most frequently exceeded on the west-facing slopes of the Norwegian mountain ranges. The minimum thresholds derived in this study are in the range of other thresholds obtained for regions with a climate comparable to Norway. Statistics reveal that the normalized threshold is more reliable than the absolute threshold as the former shows no spatial clustering of debris flows related to water supply events captured by the threshold.
23
Lainas, Spyridon, Nikolaos Depountis, and Nikolaos Sabatakakis. "Preliminary Forecasting of Rainfall-Induced Shallow Landslides in the Wildfire Burned Areas of Western Greece." Land 10, no. 8 (August 20, 2021): 877. http://dx.doi.org/10.3390/land10080877.
Анотація:
A new methodology for shallow landslide forecasting in wildfire burned areas is proposed by estimating the annual probability of rainfall threshold exceedance. For this purpose, extensive geological fieldwork was carried out in 122 landslides, which have been periodically activated in Western Greece, after the devastating wildfires that occurred in August 2007 and burned large areas in several parts of Western Greece. In addition, daily rainfall data covering more than 40 years has been collected and statistically processed to estimate the exceedance probability of the rainfall threshold above which these landslides are activated. The objectives of this study are to quantify the magnitude and duration of rainfall above which landslides in burned areas are activated, as well as to introduce a novel methodology on rainfall-induced landslide forecasting. It has been concluded that rainfall-induced landslide annual exceedance probability in the burned areas is higher when cumulative rainfall duration ranges from 6 to 9 days with local differences due to the prevailing geological conditions and landscape characteristics. The proposed methodology can be used as a basis for landslide forecasting in wildfire-affected areas, especially when triggered by rainfall, and can be further developed as a tool for preliminary landslide hazard assessment.
24
Kazemi, Ehsan, Grigorios Kyritsakas, Stewart Husband, Katrina Flavell, Vanessa Speight, and Joby Boxall. "Predicting iron exceedance risk in drinking water distribution systems using machine learning." IOP Conference Series: Earth and Environmental Science 1136, no. 1 (January 1, 2023): 012047. http://dx.doi.org/10.1088/1755-1315/1136/1/012047.
Анотація:
Abstract A Machine Learning approach has been developed to predict iron threshold exceedances in sub-regions of a drinking water distribution network from data collected the previous year. Models were trained using parameters informed by Self-Organising Map analysis based on ten years of water quality sampling data, pipe data and discolouration customer contacts from a UK network supplying over 2.3 million households. Twenty combinations of input parameters (network conditions) and three learning algorithms (Random Forests, Support Vector Machines and RUSBoost Trees) were tested. The best performing model was found to be Random Forests with input parameters of iron, turbidity, 3-day Heterotrophic Plate Counts, and high priority dead ends per District Metered Area. Different exceedance levels were tested and prediction accuracies of above 70% were achieved for UK regulatory concentration of 200 µg/L. Predicted probabilities per network sub-region were used to provide relative risk ranking to inform proactive management and investment decisions.
25
Adamkiewicz, Łukasz, Katarzyna Maciejewska, Krzysztof Skotak, Michal Krzyzanowski, Artur Badyda, Katarzyna Juda-Rezler, and Piotr Dąbrowiecki. "Health-Based Approach to Determine Alert and Information Thresholds for Particulate Matter Air Pollution." Sustainability 13, no. 3 (January 28, 2021): 1345. http://dx.doi.org/10.3390/su13031345.
Анотація:
In this study Health Impact Assessment (HIA) methods were used to evaluate potential health benefits related to keeping air pollution levels in Poland under certain threshold concentrations. Impacts of daily mean particulate matter (PM)10 levels on hospital admissions due to cardiovascular and respiratory diseases were considered. Relative risk coefficients were adopted from WHO HRAPIE project. The analyses covered period from 2015 to 2017, and were limited to the heating season (1st and 4th quarter of the year), when the highest PM10 concentrations occur. The national total number of hospital admissions attributed to PM10 concentration exceeding WHO daily Air Quality Guideline value of 50 µg/m3 was calculated for each of the 46 air quality zones established in Poland. We found that the reduction of the attributable hospital admissions by 75% or 50% of that expected for the “best case scenario”, with no days with PM10 concentration exceeding 50 µg/m3 would require avoidance of exceedance by the daily mean PM10 concentration of 64 µg/m3 and 83 µg/m3, respectively. These concentrations were proposed as the information and alert thresholds, respectively. The alert thresholds were exceeded on 2 and 38 days per year in the least and the most polluted zones, respectively. Exceedances of the information thresholds occurred on 6 and 66 days in these zones.
26
Yum, Sang-Guk, Hsi-Hsien Wei, and Sung-Hwan Jang. "Estimation of the non-exceedance probability of extreme storm surges in South Korea using tidal-gauge data." Natural Hazards and Earth System Sciences 21, no. 8 (August 26, 2021): 2611–31. http://dx.doi.org/10.5194/nhess-21-2611-2021.
Анотація:
Abstract. Global warming, one of the most serious aspects of climate change, can be expected to cause rising sea levels. These have in turn been linked to unprecedentedly large typhoons that can cause flooding of low-lying land, coastal invasion, seawater flows into rivers and groundwater, rising river levels, and aberrant tides. To prevent typhoon-related loss of life and property damage, it is crucial to accurately estimate storm-surge risk. This study therefore develops a statistical model for estimating such surges' probability based on surge data pertaining to Typhoon Maemi, which struck South Korea in 2003. Specifically, estimation of non-exceedance probability models of the typhoon-related storm surge was achieved via clustered separated peaks-over-threshold simulation, while various distribution models were fitted to the empirical data for investigating the risk of storm surges reaching particular heights. To explore the non-exceedance probability of extreme storm surges caused by typhoons, a threshold algorithm with clustering methodology was applied. To enhance the accuracy of such non-exceedance probability, the surge data were separated into three different components: predicted water level, observed water level, and surge. Sea-level data from when Typhoon Maemi struck were collected from a tidal-gauge station in the city of Busan, which is vulnerable to typhoon-related disasters due to its geographical characteristics. Fréchet, gamma, log-normal, generalized Pareto, and Weibull distributions were fitted to the empirical surge data, and the researchers compared each one's performance at explaining the non-exceedance probability. This established that Weibull distribution was better than any of the other distributions for modelling Typhoon Maemi's peak total water level. Although this research was limited to one city on the Korean Peninsula and one extreme weather event, its approach could be used to reliably estimate non-exceedance probabilities in other regions where tidal-gauge data are available. In practical terms, the findings of this study and future ones adopting its methodology will provide a useful reference for designers of coastal infrastructure.
27
Bellanger, Lise, Caroline Vigneau, Jacques Pivette, Pascale Jolliet, and Véronique Sébille. "Discrimination of psychotropic drugs over-consumers using a threshold exceedance based approach." Statistical Analysis and Data Mining: The ASA Data Science Journal 6, no. 2 (November 5, 2012): 91–101. http://dx.doi.org/10.1002/sam.11165.
28
Weiß, M. "Future water availability in selected European catchments: a probabilistic assessment of seasonal flows under the IPCC A1B emission scenario using response surfaces." Natural Hazards and Earth System Sciences 11, no. 8 (August 4, 2011): 2163–71. http://dx.doi.org/10.5194/nhess-11-2163-2011.
Анотація:
Abstract. A grid-based water balance model is used to quantify exceedance probabilities of high and low stream flow thresholds, and analyse their progression over the course of the 21st century. The analysis is carried out for 18 European river basins using the response surface method in combination with probabilistic projections of climate change, conditional to the IPCC A1B emission scenario up to 2100. According to this study, Nordic basins have the highest probability of high flow threshold violation in Europe, while in Central and Southern European basins, the probability of low flow threshold violation is highest. While the high flow violation occurs mostly during winter, with other seasons being likewise probable, low flow violation only occurs in summer. Some basins are facing an increased stream flow amplitude, having high probabilities for both, high flow and low flow violations.
29
Ha, Xuemiao, Qihe Tang, and Li Wei. "On the Maximum Exceedance of a Sequence of Random Variables Over a Renewal Threshold." Journal of Applied Probability 46, no. 2 (June 2009): 559–70. http://dx.doi.org/10.1239/jap/1245676106.
Анотація:
In this paper we study the tail behavior of the maximum exceedance of a sequence of independent and identically distributed random variables over a random walk. For both light-tailed and heavy-tailed cases, we derive a precise asymptotic formula, which extends and unifies some existing results in the recent literature of applied probability.
30
Ha, Xuemiao, Qihe Tang, and Li Wei. "On the Maximum Exceedance of a Sequence of Random Variables Over a Renewal Threshold." Journal of Applied Probability 46, no. 02 (June 2009): 559–70. http://dx.doi.org/10.1017/s0021900200005647.
Анотація:
In this paper we study the tail behavior of the maximum exceedance of a sequence of independent and identically distributed random variables over a random walk. For both light-tailed and heavy-tailed cases, we derive a precise asymptotic formula, which extends and unifies some existing results in the recent literature of applied probability.
31
Hoffmann, Peter, Christoph Menz, and Arne Spekat. "Bias adjustment for threshold-based climate indicators." Advances in Science and Research 15 (June 8, 2018): 107–16. http://dx.doi.org/10.5194/asr-15-107-2018.
Анотація:
Abstract. A method is presented which applies bias adjustments to climate indicators that are based on fixed thresholds, e.g., the number of hot days with the maximum temperature exceeding 30 ∘C or the number of days with heavy precipitation in exceedance of 20 mm rainfall. The bias adjustment first identifies the percentile of the required threshold value in reference climate data. Then it computes the value of this percentile for the individual historical climate model simulations – here an ensembles of EURO-CORDEX model runs, including dynamical and statistical models. Finally, the climate indicator is re-calculated for each model. The method is applied to climate projections as well, giving further insight into the projected development of the ensemble for extreme conditions. It is assessed that communication to the public and decision makers is improved by expressing these changes in extremes based on absolute values.
32
Dębicki, Krzysztof, and Michel Mandjes. "Exact overflow asymptotics for queues with many Gaussian inputs." Journal of Applied Probability 40, no. 3 (September 2003): 704–20. http://dx.doi.org/10.1239/jap/1059060897.
Анотація:
In this paper we consider a queue fed by a large number of independent continuous-time Gaussian processes with stationary increments. After scaling the buffer exceedance threshold and the (constant) service capacity by the number of sources, we present asymptotically exact results for the probability that the buffer threshold is exceeded. We consider both the stationary overflow probability and the (transient) probability of overflow at a finite time horizon. We give detailed results for the practically important cases in which the inputs are fractional Brownian motion processes or integrated Gaussian processes.
33
Dębicki, Krzysztof, and Michel Mandjes. "Exact overflow asymptotics for queues with many Gaussian inputs." Journal of Applied Probability 40, no. 03 (September 2003): 704–20. http://dx.doi.org/10.1017/s0021900200019653.
Анотація:
In this paper we consider a queue fed by a large number of independent continuous-time Gaussian processes with stationary increments. After scaling the buffer exceedance threshold and the (constant) service capacity by the number of sources, we present asymptotically exact results for the probability that the buffer threshold is exceeded. We consider both the stationary overflow probability and the (transient) probability of overflow at a finite time horizon. We give detailed results for the practically important cases in which the inputs are fractional Brownian motion processes or integrated Gaussian processes.
34
He, Ranran, Yuanfang Chen, Qin Huang, Wenpeng Wang, and Guofang Li. "Forecasting Summer Rainfall and Streamflow over the Yangtze River Valley Using Western Pacific Subtropical High Feature." Water 13, no. 18 (September 18, 2021): 2580. http://dx.doi.org/10.3390/w13182580.
Анотація:
The western Pacific subtropical high (WPSH) is one of the key systems affecting the summer rainfall over the Yangtze River Valley in China. In this study, the forecasting capacity of the WPSH for summer rainfall and streamflow is evaluated based on the WPSH index (WPSHI) derived from the NCEP/NCAR reanalysis dataset. It has been found that WPSHI can identify extreme flood years with a higher skill than normal wet years. Specifically, exceedance probability forecasting based on WPSHI has higher skills for higher thresholds of rainfall. For streamflow, adding WPSHI as a predictor only enhances the skill for higher thresholds of streamflow relative to models based on antecedent streamflow. Under the same framework, performances of two postprocessing approaches for dynamical forecasts, i.e., the model output statistics (MOS) approach and the reanalysis-based (RAN) approach are compared. Hindcasts from Climate Forecast System version 2 from the National Center for Environmental Prediction (CFSv2) are used to calculate WPSHI, which is used as the predictor for rainfall and streamflow. The result shows that the RAN approach performs better than the MOS approach. This study emphasizes the fact that the forecasting skill of exceedance probability would largely depend on the selected threshold of the predictand, and this fact should be noticed in future studies in the long-term forecasting field.
35
Carnevale, Claudio, Elena De Angelis, Giovanna Finzi, Enrico Turrini, and Marialuisa Volta. "Application of Data Fusion Techniques to Improve Air Quality Forecast: A Case Study in the Northern Italy." Atmosphere 11, no. 3 (February 29, 2020): 244. http://dx.doi.org/10.3390/atmos11030244.
Анотація:
Deterministic air quality forecasting models play a key role for regional and local authorities, being key tools to ensure that timely information about actual or near future exceedances of pollutant threshold values are provided to the public, as stated by the EU directive (2008/50/EC). One of the main problems of these models is that they usually underestimate some important pollutants, like PM10, especially in high-concentration areas. For this reason, the forecast of critical episodes (i.e., exceedance of 50 μ g/m 3 for PM10 concentration daily threshold) has low accuracy. To overcome this issue, several computationally fast techniques have been implemented in the last decade. In this work, two computational fast techniques are introduced, implemented and evaluated. The techniques are based on the off-line correction of the chemical transport model output in the forecasting window, estimated by means of the measurement data up to the beginning of the forecast. In particular, the techniques are based on the estimation of the correction performed as a linear combination of the corrections computed for the days when the measurements are available. The resulting system has been applied to the Lombardy region case (Northern Italy) for daily PM10 forecasting with good results.
36
Koussou, Axel, Raphaël Dumas, and Eric Desailly. "A Velocity Stretch Reflex Threshold Based on Muscle–Tendon Unit Peak Acceleration to Detect Possible Occurrences of Spasticity during Gait in Children with Cerebral Palsy." Sensors 24, no. 1 (December 20, 2023): 41. http://dx.doi.org/10.3390/s24010041.
Анотація:
Spasticity might affect gait in children with cerebral palsy. Quantifying its occurrence during locomotion is challenging. One approach is to determine kinematic stretch reflex thresholds, usually on the velocity, during passive assessment and to search for their exceedance during gait. These thresholds are determined through EMG-Onset detection algorithms, which are variable in performance and sensitive to noisy data, and can therefore lack consistency. This study aimed to evaluate the feasibility of determining the velocity stretch reflex threshold from maximal musculotendon acceleration. Eighteen children with CP were recruited and underwent clinical gait analysis and a full instrumented assessment of their soleus, gastrocnemius lateralis, semitendinosus, and rectus femoris spasticity, with EMG, kinematics, and applied forces being measured simultaneously. Using a subject-scaled musculoskeletal model, the acceleration-based stretch reflex velocity thresholds were determined and compared to those based on EMG-Onset determination. Their consistencies according to physiological criteria, i.e., if the timing of the threshold was between the beginning of the stretch and the spastic catch, were evaluated. Finally, two parameters designed to evaluate the occurrence of spasticity during gait, i.e., the proportion of the gait trial time with a gait velocity above the velocity threshold and the number of times the threshold was exceeded, were compared. The proposed method produces velocity stretch reflex thresholds close to the EMG-based ones. For all muscles, no statistical difference was found between the two parameters designed to evaluate the occurrence of spasticity during gait. Contrarily to the EMG-based methods, the proposed method always provides physiologically consistent values, with median electromechanical delays of between 50 and 130 ms. For all subjects, the semitendinosus velocity during gait usually exceeded its stretch reflex threshold, while it was less frequent for the three other muscles. We conclude that a velocity stretch reflex threshold, based on musculotendon acceleration, is a reliable substitute for EMG-based ones.
37
Turasie, Alemtsehai A. "Exceedance and Return Period of High Temperature in the African Region." Climate 9, no. 4 (March 31, 2021): 53. http://dx.doi.org/10.3390/cli9040053.
Анотація:
Several studies have indicated that the social, economic and other impacts of global warming can be linked with changes in the frequency and intensity of extreme weather/climate events. Developing countries, particularly in the African region, are highly affected by extreme events such as high temperature, usually followed/accompanied by drought. Therefore, studying the probability of occurrence and return period of extreme temperatures, and possible change in these parameters, is of high importance for climate-related policy making and preparedness works in the region. This study aims to address these issues by assessing probability of exceedance and return period of extremes in annual maximum and annual mean temperatures. The analyses of historical data in this study showed that extremes in both annual maximum and mean temperature are highly likely to be exceeded more often in the future compared to the past. For the extreme event marker (threshold) defined in this study, probability of 3 exceedances in the following 19 years (for instance), at any gridpoint, is estimated to be at least 10% for extremes in annual maxima and at least 15% for those in annual means. Most places in the region, however, have much higher (up to 20%) probability of exceedance. The estimated probability of exceedance has shown increasing tendency with time. Return period, based on the most recent data, of extremes in annual maximum temperature is found to be less than 6.5 years at about 48% of the gridpoints in the region. Similarly, return period of extremes in annual mean temperature is estimated to be less than 5.5 years at about 82% of places in the region. These estimates have also shown a strong tendency of getting shorter as time goes on. On average, extremes in annual mean temperature were found to have shorter return periods (4–7 years) compared to those in annual maximum temperature (6–10 years), at 95% confidence. The empirical results presented in this study are generally in agreement with IPCC’s projections of increased warming trend. This data-driven, robust method is used in the present study and the results can also be considered as an alternative approach for detecting changes in climate via estimating and assessing possible changes in frequency of extreme events with time.
38
Kuhnert, P. M., D. E. Pagendam, R. Bartley, D. W. Gladish, S. E. Lewis, and Z. T. Bainbridge. "Making management decisions in the face of uncertainty: a case study using the Burdekin catchment in the Great Barrier Reef." Marine and Freshwater Research 69, no. 8 (2018): 1187. http://dx.doi.org/10.1071/mf17237.
Анотація:
Modelling and monitoring pollutants entering into the Great Barrier Reef (GBR) lagoon remain important priorities for the Australian and Queensland governments. Uncertainty analysis of pollutant load delivery to the GBR would: (1) inform decision makers on their ability to meet environmental targets; (2) identify whether additional measurements are required to make confident decisions; and (3) determine whether investments into remediation activities are actually making a difference to water quality and the health of the GBR. Using a case study from the Upper Burdekin catchment where sediment concentrations are the focus, herein we explore and demonstrate different ways of communicating uncertainty to a decision maker. In particular, we show how exceedance probabilities can identify hot spots for future monitoring or remediation activities and how they can be used to inform target setting activities. We provide recommendations for water quality specialists that allow them to make more informed and scientifically defensible decisions that consider uncertainty in both the monitoring and modelling data, as well as allowing the calculation of exceedances from a threshold.
39
Monsieurs, Elise, Olivier Dewitte, and Alain Demoulin. "A susceptibility-based rainfall threshold approach for landslide occurrence." Natural Hazards and Earth System Sciences 19, no. 4 (April 15, 2019): 775–89. http://dx.doi.org/10.5194/nhess-19-775-2019.
Анотація:
Abstract. Rainfall threshold determination is a pressing issue in the landslide scientific community. While major improvements have been made towards more reproducible techniques for the identification of triggering conditions for landsliding, the now well-established rainfall intensity or event-duration thresholds for landsliding suffer from several limitations. Here, we propose a new approach of the frequentist method for threshold definition based on satellite-derived antecedent rainfall estimates directly coupled with landslide susceptibility data. Adopting a bootstrap statistical technique for the identification of threshold uncertainties at different exceedance probability levels, it results in thresholds expressed as AR = (α±Δα)⋅S(β±Δβ), where AR is antecedent rainfall (mm), S is landslide susceptibility, α and β are scaling parameters, and Δα and Δβ are their uncertainties. The main improvements of this approach consist in (1) using spatially continuous satellite rainfall data, (2) giving equal weight to rainfall characteristics and ground susceptibility factors in the definition of spatially varying rainfall thresholds, (3) proposing an exponential antecedent rainfall function that involves past daily rainfall in the exponent to account for the different lasting effect of large versus small rainfall, (4) quantitatively exploiting the lower parts of the cloud of data points, most meaningful for threshold estimation, and (5) merging the uncertainty on landslide date with the fit uncertainty in a single error estimation. We apply our approach in the western branch of the East African Rift based on landslides that occurred between 2001 and 2018, satellite rainfall estimates from the Tropical Rainfall Measurement Mission Multi-satellite Precipitation Analysis (TMPA 3B42 RT), and the continental-scale map of landslide susceptibility of Broeckx et al. (2018) and provide the first regional rainfall thresholds for landsliding in tropical Africa.
40
Tabarani, Ahmed, Abdellah Zinedine, João Miguel Rocha, Moez Sanaa, and El Hassane Abdennebi. "Comparative Study of Ochratoxin A Exposure through the Intake of Cereal Products in Two Climatic Moroccan Regions." Toxins 15, no. 7 (July 9, 2023): 452. http://dx.doi.org/10.3390/toxins15070452.
Анотація:
The present study aims to compare ochratoxin A (OTA) exposure through the intake of three cereal derivative products (bread, pasta and semolina) in two different Moroccan climatic regions (littoral and continental). OTA weekly intakes from cereal products were calculated using a deterministic approach for each region. Results showed a statistically significant difference (p < 0.05) of OTA exposure between the two regions. Indeed, the median OTA exposure was estimated at 48.97 ng/kg b.w./week in the littoral region, while it was estimated at 6.36 ng/kg b.w./week in the continental region. The probabilistic approach showed that, due to uncertainties, the 95th percentile of weekly OTA exposure associated with the three cereal products ranged from 66.18 to 137.79 (95% CI) with a median of 97.44 ng/kg body weight (b.w.)/week. Compared to the threshold of 100 ng/kg b.w./week, 95% of the cumulative distributions predicted an exceedance frequency between 0.42 and 17.30% (95% CI), with an exceedance frequency median of 4.43%. Results showed that cereal derivatives constitute an important vector of OTA exposure and cause a significant exceedance of toxicological reference value among large consumers in the littoral region, which suggests the urgency of reconsidering the maximum regulatory limit (MRL) set for OTA (3 µg/kg) in cereal derivatives by Moroccan authorities.
41
Vélez-Pereira, Andrés M., Concepción De Linares, Miquel A. Canela, and Jordina Belmonte. "A Comparison of Models for the Forecast of Daily Concentration Thresholds of Airborne Fungal Spores." Atmosphere 14, no. 6 (June 13, 2023): 1016. http://dx.doi.org/10.3390/atmos14061016.
Анотація:
Aerobiological predictive model development is of increasing interest, despite the distribution and variability of data and the limitations of statistical methods making it highly challenging. The use of concentration thresholds and models, where a binary response allows one to establish the occurrence or non-occurrence of the threshold, have been proposed to reduce difficulties. In this paper, we use logistic regression (logit) and regression trees to predict the daily concentration thresholds (low, medium, high, and very high) of six airborne fungal spore taxa (Alternaria, Cladosporium, Agaricus, Ganoderma, Leptosphaeria, and Pleospora) in eight localities in Catalonia (NE Spain) using data from 1995 to 2014. The predictive potential of these models was analyzed through sensitivity and specificity. The models showed similar results regarding the relationship and influence of the meteorological parameters and fungal spores. Ascospores showed a strong relationship with precipitation and basidiospores with minimum temperature, while conidiospores did not indicate any preferences. Sensitivity (true-positive) and specificity (false-positive) presented highly satisfactory validation results for both models in all thresholds, with an average of 73%. However, seeing as logit offers greater precision when attempting to establish the exceedance of a concentration threshold and is easier to apply, it is proposed as the best predictive model.
42
Brown, Iain, Kevin McDougall, Sreeni Chadalavada, and Md Jahangir Alam. "An Alternative Method for Estimating the Peak Flow for a Regional Catchment Considering the Uncertainty via Continuous Simulation." Water 15, no. 19 (September 25, 2023): 3355. http://dx.doi.org/10.3390/w15193355.
Анотація:
Estimating peak flow for a catchment is commonly undertaken using the design event method; however, this method does not allow for the understanding of uncertainty in the result. This research first presents a simplified method of fragments approach to rainfall disaggregation that ignores the need to consider seasonality, offering a greater diversity in storm patterns within the resulting sub-daily rainfall. By simulating 20 iterations of the disaggregated sub-daily rainfall within a calibrated continuous simulation hydrologic model, we were able to produce multiple long series of streamflow at the outlet of the catchment. With these data, we investigated the use of both the annual maximum and peaks over threshold approaches to flood frequency analysis and found that for a 1-in-100-year annual exceedance probability peak flow, the peaks over threshold method (333 m3/s ± 50 m3/s) was significantly less uncertain than the annual maximum method (427 m3/s ± 100 m3/s). For the 1-in-100-year annual exceedance probability, the median peak flow from the peaks over threshold method (333 m3/s) produced an outcome comparable to the design event method peak flow (328 m3/s), indicating that this research offers an alternative approach to estimating peak flow, with the additional benefit of understanding the uncertainty in the estimation. Finally, this paper highlighted the impact that length and period of streamflow has on peak flow estimation and noted that previous assumptions around the minimum length of gauged streamflow required for flood frequency analysis may not be appropriate in particular catchments.
43
Wu, C. Y., and S. C. Chen. "Integrating spatial and temporal probabilities for the annual landslide hazard maps in Shihmen watershed, Taiwan." Natural Hazards and Earth System Sciences Discussions 1, no. 2 (March 19, 2013): 471–508. http://dx.doi.org/10.5194/nhessd-1-471-2013.
Анотація:
Abstract. Landslide spatial probability, temporal probability, and landslide size probability were employed to perform landslide hazard assessment in this study. Following a screening process, landslide susceptibility-related factors included eleven intrinsic geomorphological factors and two extrinsic rainfall factors, which were evaluated as effective factors because of the higher correlation with the landslide distribution. Landslide area analysis was first employed to establish the power law relationship between landslide area and noncumulative number, and a probability density function was then used to convert this relationship to cumulative probability of landslide area. The exceedance probability of rainfall with different recurrence intervals was used to determine the temporal probability of those events. Finally, the landslide spatial probability, landslide area probability, and exceedance probability were integrated to estimate the annual probability of each slope-unit with a landslide area exceeding a certain threshold in a watershed. The slope-units with high landslide probability were concentrated in Taigang River watershed, which should be the leading target of future management efforts.
44
Iervolino, Iunio. "Generalized Earthquake Counting Processes for Sequence‐Based Hazard." Bulletin of the Seismological Society of America 109, no. 4 (June 11, 2019): 1435–50. http://dx.doi.org/10.1785/0120180271.
Анотація:
Abstract Sequence‐based probabilistic seismic hazard analysis (SPSHA) allows us to account for the effect of aftershocks in the assessment of seismic structural‐design actions (Iervolino et al., 2014, 2018). In fact, it generalizes classical probabilistic seismic hazard analysis (PSHA; Cornell, 1968), combining it with aftershock‐PSHA (Yeo and Cornell, 2009). SPSHA associates in time aftershocks to mainshocks and, therefore, retains a desirable property of classical PSHA; that is, events (earthquakes in PSHA and mainshock–aftershock sequences in SPSHA) occur according to homogeneous Poisson processes (HPPs). Nevertheless, the number of earthquakes in SPSHA is not Poisson‐distributed. This is addressed herein, in which the probability distribution is formulated and discussed for the following random variables: (1) the count of all earthquakes pertaining to sequences originating in any time interval; (2) the count of all earthquakes occurring in any time interval; (3) the count of all earthquakes that cause exceedance of an arbitrary ground‐motion intensity threshold at the site of interest, generated by sequences originating in any time interval. An application referring to central Italy is also developed to help the discussion. The three main findings are that: (1) the formulated SPSHA counting processes further generalize PSHA; that is, they degenerate in the corresponding mainshock HPPs, if aftershocks are neglected; (2) to associate the aftershocks to the corresponding mainshocks in time is fit for hazard assessment purposes; and (3) the variance‐to‐mean ratio of the counting distributions is significantly larger than one; consequently, the occurrence processes cannot be approximated by Poisson processes. These results, which complete the SPSHA framework, can be a reference for model calibration exercises when SPSHA is computed via simulation and in those cases in which the probability of an exact number of exceedances is of interest, rather than that of observing at least one exceedance (e.g., for seismic damage accumulation studies).
45
Wu, Chun-Yi, and Yen-Chu Yeh. "A Landslide Probability Model Based on a Long-Term Landslide Inventory and Rainfall Factors." Water 12, no. 4 (March 26, 2020): 937. http://dx.doi.org/10.3390/w12040937.
Анотація:
The prediction and advanced warning of landslide hazards in large-scale areas must deal with a large amount of uncertainty, therefore a growing number of studies are using stochastic models to analyze the probability of landslide occurrences. In this study, we used a modified Thiessen’s polygon method to divide the research area into several rain gauge control areas, and divided the control areas into slope units reflecting the topographic characteristics to enhance the spatial resolution of a landslide probability model. We used a 2000–2015 long-term landslide inventory, daily rainfall, and effective accumulated rainfall to estimate the rainfall threshold that can trigger landslides. We then employed a Poisson probability model and historical rainfall data from 1987 to 2016 to calculate the exceedance probability that rainfall events will exceed the threshold value. We calculated the number of landslides occurring from the events when rainfall exceeds the threshold value in the slope units to estimate the probability that a landslide will occur in this situation. Lastly, we employed the concept of conditional probability by multiplying this probability with the exceedance probability of rainfall events exceeding the threshold value, which yielded the probability that a landslide will occur in each slope unit for one year. The results indicated the slope units with high probability that at least one rainfall event will exceed the threshold value at the same time that one landslide will occur within any one year are largely located in the southwestern part of the Taipei Water Source Domain, and the highest probability is 0.26. These slope units are located in parts of the study area with relatively weak lithology, high elevations, and steep slopes. Compared with probability models based solely on landslide inventories, our proposed landslide probability model, combined with a long-term landslide inventory and rainfall factors, can avoid problems resulting from an incomplete landslide inventory, and can also be used to estimate landslide occurrence probability based on future potential changes in rainfall.
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Rolph, Rebecca J., Andrew R. Mahoney, John Walsh, and Philip A. Loring. "Impacts of a lengthening open water season on Alaskan coastal communities: deriving locally relevant indices from large-scale datasets and community observations." Cryosphere 12, no. 5 (May 28, 2018): 1779–90. http://dx.doi.org/10.5194/tc-12-1779-2018.
Анотація:
Abstract. Using thresholds of physical climate variables developed from community observations, together with two large-scale datasets, we have produced local indices directly relevant to the impacts of a reduced sea ice cover on Alaska coastal communities. The indices include the number of false freeze-ups defined by transient exceedances of ice concentration prior to a corresponding exceedance that persists, false break-ups, timing of freeze-up and break-up, length of the open water duration, number of days when the winds preclude hunting via boat (wind speed threshold exceedances), the number of wind events conducive to geomorphological work or damage to infrastructure from ocean waves, and the number of these wind events with on- and along-shore components promoting water setup along the coastline. We demonstrate how community observations can inform use of large-scale datasets to derive these locally relevant indices. The two primary large-scale datasets are the Historical Sea Ice Atlas for Alaska and the atmospheric output from a regional climate model used to downscale the ERA-Interim atmospheric reanalysis. We illustrate the variability and trends of these indices by application to the rural Alaska communities of Kotzebue, Shishmaref, and Utqiaġvik (previously Barrow), although the same procedure and metrics can be applied to other coastal communities. Over the 1979–2014 time period, there has been a marked increase in the number of combined false freeze-ups and false break-ups as well as the number of days too windy for hunting via boat for all three communities, especially Utqiaġvik. At Utqiaġvik, there has been an approximate tripling of the number of wind events conducive to coastline erosion from 1979 to 2014. We have also found a delay in freeze-up and earlier break-up, leading to a lengthened open water period for all of the communities examined.
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Pásztor, László, Gábor Négyesi, Annamária Laborczi, Tamás Kovács, Elemér László, and Zita Bihari. "Integrated spatial assessment of wind erosion risk in Hungary." Natural Hazards and Earth System Sciences 16, no. 11 (November 24, 2016): 2421–32. http://dx.doi.org/10.5194/nhess-16-2421-2016.
Анотація:
Abstract. Wind erosion susceptibility of Hungarian soils was mapped on the national level integrating three factors of the complex phenomenon of deflation (physical soil features, wind characteristics, and land use and land cover). Results of wind tunnel experiments on erodibility of representative soil samples were used for the parametrization of a countrywide map of soil texture compiled for the upper 5 cm layer of soil, which resulted in a map representing threshold wind velocity exceedance. Average wind velocity was spatially estimated with 0.5′ resolution using the Meteorological Interpolation based on Surface Homogenised Data Basis (MISH) method elaborated for the spatial interpolation of surface meteorological elements. The probability of threshold wind velocity exceedance was determined based on values predicted by the soil texture map at the grid locations. Ratio values were further interpolated to a finer 1 ha resolution using sand and silt content of the uppermost (0–5 cm) layer of soil as spatial co-variables. Land cover was also taken into account, excluding areas that are not relevant to wind erosion (forests, water bodies, settlements, etc.), to spatially assess the risk of wind erosion. According to the resulting map of wind erosion susceptibility, about 10 % of the total area of Hungary can be identified as susceptible to wind erosion. The map gives more detailed insight into the spatial distribution of wind-affected areas in Hungary compared to previous studies.
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Roux, Hélène, Arnau Amengual, Romu Romero, Ernest Bladé, and Marcos Sanz-Ramos. "Evaluation of two hydrometeorological ensemble strategies for flash-flood forecasting over a catchment of the eastern Pyrenees." Natural Hazards and Earth System Sciences 20, no. 2 (February 7, 2020): 425–50. http://dx.doi.org/10.5194/nhess-20-425-2020.
Анотація:
Abstract. This study aims at evaluating the performances of flash-flood forecasts issued from deterministic and ensemble meteorological prognostic systems. The hydrometeorological modeling chain includes the Weather Research and Forecasting Model (WRF) forcing the rainfall-runoff model MARINE dedicated to flash floods. Two distinct ensemble prediction systems accounting for (i) perturbed initial and lateral boundary conditions of the meteorological state and (ii) mesoscale model physical parameterizations have been implemented on the Agly catchment of the eastern Pyrenees with three subcatchments exhibiting different rainfall regimes. Different evaluations of the performance of the hydrometeorological strategies have been performed: (i) verification of short-range ensemble prediction systems and corresponding streamflow forecasts, for a better understanding of how forecasts behave; (ii) usual measures derived from a contingency table approach, to test an alert threshold exceedance; and (iii) overall evaluation of the hydrometeorological chain using the continuous rank probability score, for a general quantification of the ensemble performances. Results show that the overall discharge forecast is improved by both ensemble strategies with respect to the deterministic forecast. Threshold exceedance detections for flood warning also benefit from large hydrometeorological ensemble spread. There are no substantial differences between both ensemble strategies on these test cases in terms of both the issuance of flood warnings and the overall performances, suggesting that both sources of external-scale uncertainty are important to take into account.
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Naess, A., O. Gaidai, and O. Karpa. "Estimation of Extreme Values by the Average Conditional Exceedance Rate Method." Journal of Probability and Statistics 2013 (2013): 1–15. http://dx.doi.org/10.1155/2013/797014.
Анотація:
This paper details a method for extreme value prediction on the basis of a sampled time series. The method is specifically designed to account for statistical dependence between the sampled data points in a precise manner. In fact, if properly used, the new method will provide statistical estimates of the exact extreme value distribution provided by the data in most cases of practical interest. It avoids the problem of having to decluster the data to ensure independence, which is a requisite component in the application of, for example, the standard peaks-over-threshold method. The proposed method also targets the use of subasymptotic data to improve prediction accuracy. The method will be demonstrated by application to both synthetic and real data. From a practical point of view, it seems to perform better than the POT and block extremes methods, and, with an appropriate modification, it is directly applicable to nonstationary time series.
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Cheetham, M. D., R. T. Bush, A. F. Keene, and W. D. Erskine. "Nonsynchronous, episodic incision: Evidence of threshold exceedance and complex response as controls of terrace formation." Geomorphology 123, no. 3-4 (November 2010): 320–29. http://dx.doi.org/10.1016/j.geomorph.2010.07.024.