40 results on '"Stochastic Phenomena"'
Search Results
2. Exact solutions of Fokker–Planck equation via the Nikiforov–Uvarov method.
- Author
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Heidari, Hossein, Motavalli, Hossein, and Keramati, Mehdi Rezaei
- Abstract
We propose a powerful approach to provide the exact solutions of the time-dependent Fokker–Planck equation (FPE) for a given pair of drift and diffusion functions in stochastic phenomena. First, we briefly review Nikiforov–Uvarov mathematical method and then apply it to consider three important examples. Subsequently, the probability distribution functions of FPE are obtained in terms of special orthogonal functions for three cases, as well as the corresponding eigenvalues are derived. Several applications are proposed and it is shown that the results of our approach are in good agreement with those obtained by other methods. [ABSTRACT FROM AUTHOR]
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- 2021
- Full Text
- View/download PDF
3. Dynamic regimes of the stochastic 'prey - predatory' model with competition and saturation
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Ekaterina Pavlovna Abramova and Tatyana Vladimirovna Ryazanova
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population dynamics ,stochastic phenomena ,bistability ,Applied mathematics. Quantitative methods ,T57-57.97 ,Mathematics ,QA1-939 - Abstract
We consider "predator - prey" model taking into account the competition of prey, predator for different from the prey resources, and their interaction described by the second type Holling trophic function. An analysis of the attractors is carried out depending on the coefficient of competition of predators. In the deterministic case, this model demonstrates the complex behavior associated with the local (Andronov -Hopf and saddlenode) and global (birth of a cycle from a separatrix loop) bifurcations. An important feature of this model is the disappearance of a stable cycle due to a saddle-node bifurcation. As a result of the presence of competition in both populations, parametric zones of mono- and bistability are observed. In parametric zones of bistability the system has either coexisting two equilibria or a cycle and equilibrium. Here, we investigate the geometrical arrangement of attractors and separatrices, which is the boundary of basins of attraction. Such a study is an important component in understanding of stochastic phenomena. In this model, the combination of the nonlinearity and random perturbations leads to the appearance of new phenomena with no analogues in the deterministic case, such as noise-induced transitions through the separatrix, stochastic excitability, and generation of mixed-mode oscillations. For the parametric study of these phenomena, we use the stochastic sensitivity function technique and the confidence domain method. In the bistability zones, we study the deformations of the equilibrium or oscillation regimes under stochastic perturbation. The geometric criterion for the occurrence of such qualitative changes is the intersection of confidence domains and the separatrix of the deterministic model. In the zone of monostability, we evolve the phenomena of explosive change in the size of population as well as extinction of one or both populations with minor changes in external conditions. With the help of the confidence domains method, we solve the problem of estimating the proximity of a stochastic population to dangerous boundaries, upon reaching which the coexistence of populations is destroyed and their extinction is observed.
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- 2019
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- View/download PDF
4. Data-driven stochastic AC-OPF using Gaussian process regression.
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Mitrovic, Mile, Lukashevich, Aleksandr, Vorobev, Petr, Terzija, Vladimir, Budennyy, Semen, Maximov, Yury, and Deka, Deepjyoti
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KRIGING , *RENEWABLE energy sources , *GREENHOUSE gases , *DISTRIBUTION (Probability theory) , *ELECTRICAL load , *WIND power - Abstract
At present, electricity generation is responsible for more than a quarter of the greenhouse gas emissions in the US. Integrating significant amounts of renewable energy sources into a power grid is probably the most accessible way to reduce carbon emissions from power grids and slow down climate change. Unfortunately, the most accessible renewable power sources, such as wind and solar, are highly intermittent and thus bring a lot of uncertainty to power grid operation and challenge existing optimization and control policies. The chance-constrained (CC) alternating current optimal power flow (AC-OPF) framework finds the minimum cost of generation dispatch, maintaining the power grid operation within security limits with a prescribed probability. Unfortunately, the AC-OPF problem's chance-constrained extension is non-convex, computationally challenging, and requires knowledge of system parameters and also needs additional assumptions to be made about the behavior of renewable generation probability distribution. Known linear and convex approximations to the above problems, though tractable, are too conservative for operational practice and do not consider uncertainty in system parameters. This paper presents an alternative data-driven approach for solving the stochastic AC-OPF problem, based on Gaussian process regression (GPR) to close this gap. The Gaussian process (GP) approach learns a simple yet non-convex data-driven approximation to the AC power flow equations that can incorporate uncertain inputs. The latter is then used to determine the solution of CC-OPF efficiently, by accounting for both input and parameter uncertainty. The practical efficiency of the proposed approach using different approximations for GP-uncertainty propagation is validated and illustrated using a number of standard IEEE test cases. • Chance constrained optimal power flow based on data-driven approach. • Gaussian process regression for solving stochastic optimal power flow. • Gaussian processes for handling uncertainties in power systems. • Machine learning for power system optimization. [ABSTRACT FROM AUTHOR]
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- 2023
- Full Text
- View/download PDF
5. Optimal paths and large fluctuations
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Arrayas, Manuel
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510 ,Stochastic phenomena - Published
- 1998
6. Drought Conditions Enhance Groundwater Table Fluctuations Caused by Hydropower Plant Management
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Basilio Hazas, M., Marcolini, G., Castagna, M., Galli, M., Singh, T., Wohlmuth, B., Chiogna, G., 1 School of Engineering and Design Technical University of Munich Munich Germany, and 2 Department of Numerical Mathematics Technical University of Munich Garching Germany
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GENERAL ,Climate and interannual variability ,Numerical modeling ,Time series experiments ,NATURAL HAZARDS ,Atmospheric ,Geological ,Oceanic ,Physical modeling ,Climate impact ,Risk ,Disaster risk analysis and assessment ,Preparedness and planning ,NONLINEAR GEOPHYSICS ,Probability distributions, heavy and fat-tailed ,Scaling: spatial and temporal ,OCEANOGRAPHY: PHYSICAL ,Air/sea interactions ,Decadal ocean variability ,Ocean influence of Earth rotation ,Sea level: variations and mean ,Surface waves and tides ,Tsunamis and storm surges ,PALEOCEANOGRAPHY ,POLICY SCIENCES ,Benefit-cost analysis ,Regional planning ,RADIO SCIENCE ,Radio oceanography ,SEISMOLOGY ,Earthquake ground motions and engineering seismology ,Volcano seismology ,SPACE PLASMA PHYSICS ,Stochastic phenomena ,VOLCANOLOGY ,Volcano/climate interactions ,Atmospheric effects ,Volcano monitoring ,Effusive volcanism ,Mud volcanism ,Explosive volcanism ,Volcanic hazards and risks ,Research Article ,surface water-groundwater interaction ,hydropower ,managed rivers ,groundwater modeling [ATMOSPHERIC COMPOSITION AND STRUCTURE ,Air/sea constituent fluxes ,Volcanic effects ,BIOGEOSCIENCES ,Climate dynamics ,Modeling ,COMPUTATIONAL GEOPHYSICS ,Numerical solutions ,CRYOSPHERE ,Avalanches ,Mass balance ,GEODESY AND GRAVITY ,Ocean monitoring with geodetic techniques ,Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions ,Global change from geodesy ,GLOBAL CHANGE ,Abrupt/rapid climate change ,Climate variability ,Earth system modeling ,Impacts of global change ,Land/atmosphere interactions ,Oceans ,Regional climate change ,Sea level change ,Solid Earth ,Water cycles ,HYDROLOGY ,Groundwater hydrology ,Groundwater/surface water interaction ,Time series analysis ,Water management ,Climate impacts ,Extreme events ,Hydrological cycles and budgets ,INFORMATICS ,Temporal analysis and representation ,MARINE GEOLOGY AND GEOPHYSICS ,Gravity and isostasy ,MATHEMATICAL GEOPHYSICS ,Persistence, memory, correlations, clustering ,Stochastic processes ,ATMOSPHERIC PROCESSES ,Climate change and variability ,Climatology ,General circulation ,Ocean/atmosphere interactions ,Regional modeling ,Theoretical modeling ,OCEANOGRAPHY] ,groundwater modeling ,ddc:551 ,surface water‐groundwater interaction ,ddc ,Water Science and Technology - Abstract
Management of hydropower plants strongly influences streamflow dynamics and hence the interaction between surface water and groundwater. As dam operations cause variations in river stages, these can result in changes in the groundwater level at multiple temporal scales. In this work, we study the case of an Alpine aquifer, where weekly fluctuations are particularly pronounced. We consider an area with four river reaches differently impacted by reservoir operations and investigate the influence of these rivers on the common aquifer. Using continuous wavelet transform and wavelet coherence analysis, we show that weekly fluctuations in the groundwater table are particularly pronounced in dry years, in particular in the winter season, although the area of the aquifer impacted by dam operations remains almost unchanged. We thus observe that in Alpine catchments, surface water‐groundwater interaction is sensitive to the conditions determined by a specific hydrological year. We also investigate the influences of the river‐aquifer water fluxes and show that under dry conditions hydropeaking mainly affects their temporal dynamics. Our observations have significant consequences for predicting nutrient and temperature dynamics/regimes in river‐aquifer systems impacted by hydropower plant management., Plain Language Summary: The operation of hydropower plants affects the water level in the downstream part of the river, which in turn can alter the groundwater level. In this work, we study an Alpine aquifer crossed by rivers differently impacted by hydropower production. We use statistical tools to analyze the interaction between the rivers and the groundwater, and observe that this interaction is sensitive to the conditions of the hydrological year, such as dry periods., Key Points: Wavelet power spectrum and coherence analysis is used to study river‐aquifer interactions under dam operations in an Alpine catchment. The impact of reservoir operations on the aquifer is strongest under low flow conditions but the area impacted shows little variation. Under low flow conditions, dam operations considerably influence the frequency of the water exchange between rivers and aquifer., Consejo Nacional de Ciencia y Tecnología http://dx.doi.org/10.13039/501100003141, Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659, Consejo Veracruzano de Investigación Científica y Desarrollo Tecnológico, https://doi.org/10.17632/97jchhz4s8.2
- Published
- 2022
7. Association Between Air Pollutants and Acute Exacerbation of Chronic Obstructive Pulmonary Disease: A Time Stratified Case‐Crossover Design With a Distributed Lag Nonlinear Model
- Author
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Yanchen Liu, Xiaoli Han, Xudong Cui, Xiangkai Zhao, Xin Zhao, Hongmiao Zheng, Benzhong Zhang, and Xiaowei Ren
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Epidemiology ,Biogeosciences ,Volcanic Effects ,Global Change from Geodesy ,Oceanography: Biological and Chemical ,Atmospheric PM2.5 in China: indoor, outdoor, and health effects ,Volcanic Hazards and Risks ,time‐stratified case‐crossover study ,Oceans ,Sea Level Change ,Stochastic Phenomena ,Disaster Risk Analysis and Assessment ,Waste Management and Disposal ,Water Science and Technology ,Global and Planetary Change ,Marine Pollution ,Climate and Interannual Variability ,Pollution ,Climate Impact ,Earthquake Ground Motions and Engineering Seismology ,Explosive Volcanism ,Earth System Modeling ,Atmospheric Processes ,Probability Distributions, Heavy and Fat‐tailed ,Public Health ,Ocean Monitoring with Geodetic Techniques ,Ocean/Atmosphere Interactions ,Mathematical Geophysics ,Atmospheric ,Regional Modeling ,Atmospheric Effects ,Volcanology ,Temporal Analysis and Representation ,Megacities and Urban Environment ,Management, Monitoring, Policy and Law ,Hydrological Cycles and Budgets ,Decadal Ocean Variability ,Land/Atmosphere Interactions ,Extreme Events ,Geodesy and Gravity ,Global Change ,Time Series Analysis ,Air/Sea Interactions ,Numerical Modeling ,Urban Systems ,Solid Earth ,Geological ,Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions ,AECOPD ,Water Cycles ,Public Health, Environmental and Occupational Health ,Modeling ,Aerosols and Particles ,Avalanches ,Volcano Seismology ,Benefit‐cost Analysis ,respiratory tract diseases ,distributed lag nonlinear model ,air pollutants ,Space Plasma Physics ,Computational Geophysics ,Regional Climate Change ,Scaling: Spatial and Temporal ,Natural Hazards ,Abrupt/Rapid Climate Change ,Informatics ,Health, Toxicology and Mutagenesis ,Pollution: Urban, Regional and Global ,Surface Waves and Tides ,Atmospheric Composition and Structure ,Time Series Experiments ,Volcano Monitoring ,Seismology ,Climatology ,Nonlinear Geophysics ,Radio Oceanography ,Geohealth ,Gravity and Isostasy ,Marine Geology and Geophysics ,Physical Modeling ,Oceanography: General ,Pollution: Urban and Regional ,Cryosphere ,Impacts of Global Change ,Oceanography: Physical ,Research Article ,Risk ,Persistence, Memory, Correlations, Clustering ,Oceanic ,Theoretical Modeling ,complex mixtures ,Radio Science ,Tsunamis and Storm Surges ,Paleoceanography ,Climate Dynamics ,Numerical Solutions ,Climate Change and Variability ,Aerosols ,Stochastic Processes ,Effusive Volcanism ,Climate Variability ,General Circulation ,Policy Sciences ,Climate Impacts ,Mud Volcanism ,Air/Sea Constituent Fluxes ,Mass Balance ,Ocean influence of Earth rotation ,Volcano/Climate Interactions ,Hydrology ,Sea Level: Variations and Mean - Abstract
Acute exacerbation of chronic obstruction pulmonary disease (AECOPD) as a respiratory disease, is considered to be related to air pollution by more and more studies. However, the evidence on how air pollution affect the incidence of AECOPD and whether there are population differences is still insufficient. Therefore, we select PM10, PM2.5, SO2, NO2, CO, and O3 as representatives combined with daily AECOPD admission data from 1 January 2015 to 26 June 2016 in the rural areas of Qingyang, northwestern China to explore the associations of air pollution with AECOPD. Based on a time‐stratified case‐crossover design, we constructed a distributed lag nonlinear model to qualify the single and cumulative lagged effects of air pollution on AECOPD. Stratified related risks by sex and age were also reported. The cumulative exposure‐response curves were approximately linear for PM2.5, “V”‐shaped for PM10, “U”‐shaped for NO2 and inverted‐“V” for SO2, CO and O3. Exposure to high‐PM2.5 (42 μg/m3), high‐PM10 (91 μg/m3), high‐SO2 (58 μg/m3), low‐NO2 (12 μg/m3), and high‐CO (1.55 mg/m3) increased the risk of AECOPD. Females aged 15–64 were more susceptible under extreme concentrations of PM2.5, SO2, CO, and low‐PM10 than other subgroups. In addition, adults aged 15–64 were more sensitive to extreme concentrations of NO2 compared with the elderly ≥65 years old, while the latter were more sensitive to high‐PM10. High‐SO2, high‐NO2, and extreme concentrations of PM2.5 had the greatest effects on the day of exposure, while low‐SO2 and low‐CO had lagged effects on AECOPD. Precautionary measures should be taken with a focus on vulnerable subgroups, to control hospitalization for AECOPD associated with air pollutants., Key Points Exposure to high‐PM2.5, high‐PM10, high‐SO2, low‐NO2, and high‐CO increased the risk of acute exacerbation of chronic obstruction pulmonary disease (COPD)The cumulative curves were approximately linear for PM2.5, “V”‐shaped for PM10, “U”‐shaped for NO2 and inverted‐”V” for SO2, CO and O3 The nonlinear effects on acute exacerbation of COPD at different lags varied based on the air pollutants, involved gender and age
- Published
- 2022
8. Mapping Heat Vulnerability Index Based on Different Urbanization Levels in Nebraska, USA
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Michael J. Hayes, Rezaul Mahmood, Azar M. Abadi, Clinton M. Rowe, Jesse E. Bell, Babak Jalalzadeh Fard, Rachel E. Lookadoo, Sharon Medcalf, and Martha Shulski
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Informatics ,Persistence, Memory, Correlations, Clustering ,Vulnerability index ,Epidemiology ,Health, Toxicology and Mutagenesis ,Vulnerability ,heat vulnerability index ,factor analysis ,environmental health ,Climate change ,Temporal Analysis and Representation ,Time Series Experiments ,Management, Monitoring, Policy and Law ,Environmental protection ,heatwave ,Extreme Events ,Urbanization ,TD169-171.8 ,Stochastic Phenomena ,Time Series Analysis ,Urban heat island ,Socioeconomics ,Waste Management and Disposal ,Socioeconomic status ,Water Science and Technology ,Stochastic Processes ,Global and Planetary Change ,Nonlinear Geophysics ,Public Health, Environmental and Occupational Health ,Geohealth ,Nebraska ,rural heatwave ,Pollution ,Oceanography: General ,Geography ,Probability Distributions, Heavy and Fat‐tailed ,Space Plasma Physics ,Residence ,Impacts of Climate Change: Human Health ,Public Health ,Hydrology ,Rural area ,Scaling: Spatial and Temporal ,Mathematical Geophysics ,Natural Hazards ,Research Article - Abstract
Heatwaves cause excess mortality and physiological impacts on humans throughout the world, and climate change will intensify and increase the frequency of heat events. Many adaptation and mitigation studies use spatial distribution of highly vulnerable local populations to inform heat reduction and response plans. However, most available heat vulnerability studies focus on urban areas with high heat intensification by Urban Heat Islands (UHIs). Rural areas encompass different environmental and socioeconomic issues that require alternate analyses of vulnerability. We categorized Nebraska census tracts into four urbanization levels, then conducted factor analyses on each group and captured different patterns of socioeconomic vulnerabilities among resultant Heat Vulnerability Indices (HVIs). While disability is the major component of HVI in two urbanized classes, lower education, and races other than white have higher contributions in HVI for the two rural classes. To account for environmental vulnerability of HVI, we considered different land type combinations for each urban class based on their percentage areas and their differences in heat intensifications. Our results demonstrate different combinations of initial variables in heat vulnerability among urban classes of Nebraska and clustering of high and low heat vulnerable areas within the highest urbanized sections. Less urbanized areas show no spatial clustering of HVI. More studies with separation on urbanization level of residence can give insights into different socioeconomic vulnerability patterns in rural and urban areas, while also identifying changes in environmental variables that better capture heat intensification in rural settings., Key Points Despite similar incidence rates, Heat Vulnerability Index (HVI) in rural areas is under studied in comparison to urban areasThe environmental vulnerability variables in rural areas are dissimilar to urban areas, so we applied different variables to calculate themWe found different organization of socioeconomic variables in calculated HVIs, suggesting separate heat strategies for urbanization levels
- Published
- 2021
9. Human Mobility to Parks under the COVID-19 Pandemic and Wildfire Seasons in the Western and Central United States
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Jue Yang, Anni Yang, Rongting Xu, Yaqian He, Di Yang, Han Qiu, and Amanda Aragon
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Epidemiology ,Air pollution ,Biogeosciences ,Volcanic Effects ,Global Change from Geodesy ,Volcanic Hazards and Risks ,Oceans ,Sea Level Change ,Per capita ,Stochastic Phenomena ,Socioeconomics ,Disaster Risk Analysis and Assessment ,Waste Management and Disposal ,Water Science and Technology ,Global and Planetary Change ,Social distance ,Climate and Interannual Variability ,COVID‐19 pandemic ,Pollution ,Climate Impact ,Geography ,Earthquake Ground Motions and Engineering Seismology ,Explosive Volcanism ,Earth System Modeling ,Atmospheric Processes ,Probability Distributions, Heavy and Fat‐tailed ,Public Health ,Ocean Monitoring with Geodetic Techniques ,Ocean/Atmosphere Interactions ,Mathematical Geophysics ,Atmospheric ,Regional Modeling ,Atmospheric Effects ,Volcanology ,Temporal Analysis and Representation ,Management, Monitoring, Policy and Law ,Hydrological Cycles and Budgets ,Decadal Ocean Variability ,Land/Atmosphere Interactions ,Extreme Events ,Natural hazard ,TD169-171.8 ,Geodesy and Gravity ,Global Change ,Time Series Analysis ,Air/Sea Interactions ,Recreation ,Numerical Modeling ,Solid Earth ,Geological ,Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions ,Water Cycles ,Public Health, Environmental and Occupational Health ,Modeling ,Avalanches ,Volcano Seismology ,Benefit‐cost Analysis ,park visitation ,smoke ,Space Plasma Physics ,Computational Geophysics ,Regional Climate Change ,Scaling: Spatial and Temporal ,Natural Hazards ,Abrupt/Rapid Climate Change ,Informatics ,Health, Toxicology and Mutagenesis ,Surface Waves and Tides ,Atmospheric Composition and Structure ,Time Series Experiments ,medicine.disease_cause ,Environmental protection ,Volcano Monitoring ,wildfire ,Human health ,Pandemic ,Seismology ,Climatology ,Nonlinear Geophysics ,Radio Oceanography ,Geohealth ,Gravity and Isostasy ,Marine Geology and Geophysics ,Physical Modeling ,Oceanography: General ,Impacts of Climate Change: Human Health ,Cryosphere ,Impacts of Global Change ,Oceanography: Physical ,Research Article ,Risk ,Persistence, Memory, Correlations, Clustering ,Coronavirus disease 2019 (COVID-19) ,Oceanic ,Theoretical Modeling ,Radio Science ,Tsunamis and Storm Surges ,Paleoceanography ,Climate Dynamics ,medicine ,human mobility ,Numerical Solutions ,Climate Change and Variability ,Stochastic Processes ,Effusive Volcanism ,Climate Variability ,General Circulation ,Policy Sciences ,Climate Impacts ,Mud Volcanism ,Air/Sea Constituent Fluxes ,Mass Balance ,Ocean influence of Earth rotation ,Volcano/Climate Interactions ,Hydrology ,Sea Level: Variations and Mean ,human activities - Abstract
In 2020, people's health suffered a great crisis under the dual effects of the COVID‐19 pandemic and the extensive, severe wildfires in the western and central United States. Parks, including city, national, and cultural parks, offer a unique opportunity for people to maintain their recreation behaviors following the social distancing protocols during the pandemic. However, massive forest wildfires in western and central US, producing harmful toxic gases and smoke, pose significant threats to human health and affect their recreation behaviors and mobility to parks. In this study, we employed the geographically and temporally weighted regression (GTWR) Models to investigate how COVID‐19 and wildfires jointly shaped human mobility to parks, regarding the number of visits per capita, dwell time, and travel distance to parks, during June ‐ September 2020. We detected strong correlations between visitations and COVID‐19 incidence in southern Montana, western Wyoming, Colorado, and Utah before August. However, the pattern was weakened over time, indicating the decreasing trend of the degree of concern regarding the pandemic. Moreover, more park visits and lower dwell time were found in parks further away from wildfires and less air pollution in Washington, Oregon, California, Colorado, and New Mexico, during the wildfire season, suggesting the potential avoidance of wildfires when visiting parks. This study provides important insights on people's responses in recreation and social behaviors when facing multiple severe crises that impact their health and wellbeing, which could support the preparation and mitigation of the health impacts from future pandemics and natural hazards., Key Points We investigated human mobility patterns to parks under COVID‐19 pandemic and wildfire season in western and central United StatesWe found a general trend of avoidance to the parks with fewer visits and dwell time in the places with high COVID‐19 casesWith special demand of physical activities in pandemic, people travel further and spend longer time at the parks away from the wildfires
- Published
- 2021
10. Accounting for Transport Error in Inversions: An Urban Synthetic Data Experiment
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Subhomoy Ghosh, James R. Whetstone, K. L. Mueller, and Kuldeep R. Prasad
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Informatics ,Astronomy ,green house gases ,Time Series Experiments ,error covariance ,Stochastic Phenomena ,Remote Sensing and Electromagnetic Processes ,Parametric statistics ,QE1-996.5 ,Ionospheric Propagation ,Fourier Analysis ,Nonlinear Geophysics ,Uncertainty ,Geology ,Covariance ,regularization ,Oceanography: General ,Shock Waves ,Spatial Modeling ,Ensemble Transform Kalman Filter ,Probability Distributions, Heavy and Fat‐tailed ,Uncertainty Quantification ,Mathematical Geophysics ,Algorithm ,Research Article ,Persistence, Memory, Correlations, Clustering ,QB1-991 ,Temporal Analysis and Representation ,Context (language use) ,Wavelet Transform ,Environmental Science (miscellaneous) ,Spatial Analysis and Representation ,Synthetic data ,Radio Science ,Greenhouse Gases ,inversion ,Paleoceanography ,Extreme Events ,Inverse Theory ,Robustness (computer science) ,Solitons and Solitary Waves ,Time Series Analysis ,Ionosphere ,Spatial Analysis ,Stochastic Processes ,Electromagnetics ,Uncertainty Assessment ,Inversion (meteorology) ,Kalman filter ,Spectral Analysis ,Nonlinear Waves, Shock Waves, Solitons ,Space Plasma Physics ,General Earth and Planetary Sciences ,Environmental science ,Errors-in-variables models ,Computational Geophysics ,Wave Propagation ,Hydrology ,Scaling: Spatial and Temporal ,Natural Hazards - Abstract
We present and discuss the use of a high‐dimensional computational method for atmospheric inversions that incorporates the space‐time structure of transport and dispersion errors. In urban environments, transport and dispersion errors are largely the result of our inability to capture the true underlying transport of greenhouse gas (GHG) emissions to observational sites. Motivated by the impact of transport model error on estimates of fluxes of GHGs using in situ tower‐based mole‐fraction observations, we specifically address the need to characterize transport error structures in high‐resolution large‐scale inversion models. We do this using parametric covariance functions combined with shrinkage‐based regularization methods within an Ensemble Transform Kalman Filter inversion setup. We devise a synthetic data experiment to compare the impact of transport and dispersion error component of the model‐data mismatch covariance choices on flux retrievals and study the robustness of the method with respect to fewer observational constraints. We demonstrate the analysis in the context of inferring CO2 fluxes starting with a hypothesized prior in the Washington D.C. /Baltimore area constrained by a synthetic set of tower‐based CO2 measurements within an observing system simulation experiment framework. This study demonstrates the ability of these simple covariance structures to substantially improve the estimation of fluxes over standard covariance models in flux estimation from urban regions., Key Points Urban‐scale transport errors are correlated in space and time, which should be included in atmospheric inversions that estimate greenhouse gas emissionsIn a synthetic data study, multiple methods to characterize correlated errors with model‐data covariance matrices demonstrate a better performanceOverall, dynamically adaptive covariance structures perform better than standard parametric models in both recovering total fluxes and their spatial distributions
- Published
- 2021
11. Optimizing Spatial Allocation of COVID‐19 Vaccine by Agent‐Based Spatiotemporal Simulations
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Junwen Lu, Shuli Zhou, Suhong Zhou, and Zhong Zheng
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Informatics ,Operations research ,Epidemiology ,Computer science ,Health, Toxicology and Mutagenesis ,Attack rate ,Time Series Experiments ,Environmental protection ,law.invention ,Resource (project management) ,law ,Stochastic Phenomena ,Remote Sensing and Electromagnetic Processes ,Waste Management and Disposal ,Water Science and Technology ,Global and Planetary Change ,Ionospheric Propagation ,Fourier Analysis ,Nonlinear Geophysics ,Geohealth ,Pollution ,Agent‐based Models ,Vaccination ,Oceanography: General ,Transmission (mechanics) ,Shock Waves ,Spatial Modeling ,Probability Distributions, Heavy and Fat‐tailed ,Public Health ,The COVID‐19 pandemic: linking health, society and environment ,Mathematical Geophysics ,Research Article ,Persistence, Memory, Correlations, Clustering ,Temporal Analysis and Representation ,Context (language use) ,Wavelet Transform ,Management, Monitoring, Policy and Law ,Spatial Analysis and Representation ,Radio Science ,Herd immunity ,Extreme Events ,TD169-171.8 ,Solitons and Solitary Waves ,Time Series Analysis ,Ionosphere ,Spatial Analysis ,Stochastic Processes ,business.industry ,Public Health, Environmental and Occupational Health ,Electromagnetics ,Geospatial ,Usability ,Spectral Analysis ,Nonlinear Waves, Shock Waves, Solitons ,Mobile phone ,Space Plasma Physics ,Computational Geophysics ,Wave Propagation ,Hydrology ,Scaling: Spatial and Temporal ,business ,Natural Hazards - Abstract
Optimizing allocation of vaccine, a highly scarce resource, is an urgent and critical issue during fighting against on‐going COVID‐19 epidemic. Prior studies suggested that vaccine should be prioritized by age and risk groups, but few of them have considered the spatial prioritization strategy. This study aims to examine the spatial heterogeneity of COVID‐19 transmission in the city naturally, and optimize vaccine distribution strategies considering spatial prioritization. We proposed an integrated spatial model of agent‐based model and SEIR (susceptible‐exposed‐infected‐recovered). It simulated spatiotemporal process of COVID‐19 transmission in a realistic urban context. Individual movements were represented by trajectories of 8,146 randomly sampled mobile phone users on December 28, 2016 in Guangzhou, China, 90% of whom aged 18–60. Simulations were conducted under seven scenarios. Scenarios 1 and 2 examined natural spreading process of COVID‐19 and its final state of herd immunity. Scenarios 3–6 applied four vaccination strategies (random strategy, age strategy, space strategy, and space & age strategy), and identified the optimal vaccine strategy. Scenario 7 assessed the most appropriate vaccine coverage. The results demonstrates herd immunity is heterogeneously distributed in space, thus, vaccine intervention strategies should be spatialized. Among four strategies, space & age strategy is substantially most efficient, with 7.7% fewer in attack rate and 44 days longer than random strategy under 20% vaccine uptake. Space & age strategy requires 30%–40% vaccine coverage to control the epidemic, while the coverage for a random strategy is 60%–70% as a comparison. The application of our research would greatly improves the effectiveness of the vaccine usability., Key Points Spatial heterogeneity in herd immunity rate has been identifiedSpace & age strategy is substantially considered as the most efficient strategy among four vaccination strategies30%–40% vaccine coverage are needed to control the epidemic under space & age strategy, while 60%–70% for a random strategy as a comparison
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- 2021
12. What Are the Different Measures of Mobility Telling Us About Surface Transportation CO2 Emissions During the COVID‐19 Pandemic?
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Ankit Shekhar, Jia Chen, Frank N. Keutsch, Johannes Gensheimer, Alexander J. Turner, and Adrian Wenzel
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Atmospheric Science ,2019-20 coronavirus outbreak ,Informatics ,Persistence, Memory, Correlations, Clustering ,010504 meteorology & atmospheric sciences ,Coronavirus disease 2019 (COVID-19) ,Temporal Analysis and Representation ,Time Series Experiments ,Biogeosciences ,01 natural sciences ,Greenhouse Gases ,Paleoceanography ,Trace gas emissions ,Extreme Events ,Earth and Planetary Sciences (miscellaneous) ,Econometrics ,Stochastic Phenomena ,Time Series Analysis ,Proxy (statistics) ,0105 earth and related environmental sciences ,Stochastic Processes ,Nonlinear Geophysics ,Climate and Dynamics ,Data Sets ,Data and Information Discovery ,Traffic flow ,Original data ,Oceanography: General ,Geophysics ,Work (electrical) ,Space and Planetary Science ,Probability Distributions, Heavy and Fat‐tailed ,Environmental science ,Space Plasma Physics ,The COVID‐19 pandemic: linking health, society and environment ,Hydrology ,Scaling: Spatial and Temporal ,Trace Gases ,Mathematical Geophysics ,Atmospheric emissions ,Natural Hazards ,Research Article - Abstract
The COVID-19 pandemic led to widespread reductions in mobility and induced observable changes in atmospheric emissions. Recent work has employed novel mobility data sets as a proxy for trace gas emissions from traffic by scaling CO2 emissions linearly with those near-real-time mobility data. Yet, there has been little work evaluating these emission numbers. Here, we systematically compare these mobility data sets to traffic data from local governments in seven diverse urban and national/state regions to characterize the magnitude of errors that result from using the mobility data. We observe differences in excess of 60% between these mobility data sets and local traffic data. We could not find a general functional relationship between the mobility data and traffic flow over all the regions and observe higher deviations from using such general relationships than the original data. Finally, we give an overview of the potential errors that come from estimating CO2 emissions using (mobility or traffic) activity data. Future work should be cautious while using these mobility metrics for emission estimates., Journal of Geophysical Research: Atmospheres, 126 (11), ISSN:0148-0227, ISSN:2169-897X
- Published
- 2021
13. Health Impact Assessment of the 2020 Washington State Wildfire Smoke Episode: Excess Health Burden Attributable to Increased PM2.5 Exposures and Potential Exposure Reductions
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Yisi Liu, Timothy Gould, Elena Austin, Timothy V. Larson, Edmund Seto, and Jianbang Xiang
- Subjects
Informatics ,Epidemiology ,Health, Toxicology and Mutagenesis ,Pollution: Urban, Regional and Global ,Wood smoke ,Atmospheric Composition and Structure ,Time Series Experiments ,Biogeosciences ,Environmental protection ,Oceanography: Biological and Chemical ,Medicine ,Stochastic Phenomena ,Waste Management and Disposal ,Water Science and Technology ,Excess mortality ,Global and Planetary Change ,Potential impact ,Nonlinear Geophysics ,Marine Pollution ,Geohealth ,Pollution ,preparedness ,Oceanography: General ,Pollution: Urban and Regional ,fine particulate matter ,Probability Distributions, Heavy and Fat‐tailed ,health impact assessment ,wildfires ,Impacts of Climate Change: Human Health ,Public Health ,Health impact assessment ,Mathematical Geophysics ,Health Impact ,Research Article ,Persistence, Memory, Correlations, Clustering ,Temporal Analysis and Representation ,Megacities and Urban Environment ,Management, Monitoring, Policy and Law ,complex mixtures ,Paleoceanography ,Extreme Events ,Environmental health ,TD169-171.8 ,West coast ,Time Series Analysis ,Urban Systems ,Smoke ,Aerosols ,Stochastic Processes ,business.industry ,Public Health, Environmental and Occupational Health ,Odds ratio ,Aerosols and Particles ,mortality ,wildland fires ,Fire in the Earth System ,Space Plasma Physics ,Hydrology ,business ,Scaling: Spatial and Temporal ,Natural Hazards - Abstract
Major wildfires starting in the summer of 2020 along the west coast of the United States made PM2.5 concentrations in this region rank among the highest in the world. Washington was impacted both by active wildfires in the state and aged wood smoke transported from fires in Oregon and California. This study aims to estimate the magnitude and disproportionate spatial impacts of increased PM2.5 concentrations attributable to these wildfires on population health. Daily PM2.5 concentrations for each county before and during the 2020 Washington wildfire episode (September 7–19) were obtained from regulatory air monitors. Utilizing previously established concentration‐response function (CRF) of PM2.5 (CRF of total PM2.5) and odds ratio (OR) of wildfire smoke days (OR of wildfire smoke days) for mortality, we estimated excess mortality attributable to the increased PM2.5 concentrations in Washington. On average, daily PM2.5 concentrations increased 97.1 μg/m3 during the wildfire smoke episode. With CRF of total PM2.5, the 13‐day exposure to wildfire smoke was estimated to lead to 92.2 (95% CI: 0.0, 178.7) more all‐cause mortality cases; with OR of wildfire smoke days, 38.4 (95% CI: 0.0, 93.3) increased all‐cause mortality cases and 15.1 (95% CI: 0.0, 27.9) increased respiratory mortality cases were attributable to the wildfire smoke episode. The potential impact of avoiding elevated PM2.5 exposures during wildfire events significantly reduced the mortality burden. Because wildfire smoke episodes are likely to impact the Pacific Northwest in future years, continued preparedness and mitigations to reduce exposures to wildfire smoke are necessary to avoid excess health burden., Key Points Elevated PM2.5 levels from a wildfire smoke episode were estimated to place a heavy mortality burden on counties in western WashingtonCounties in central and eastern Washington were estimated to have the highest per‐capita mortality during the wildfire smoke episodeReducing 40% of PM2.5 exposure for people below the federal poverty level was associated with 4.1 (95% CI: 0.0, 8.2) reduced all‐cause deaths
- Published
- 2021
14. Adapting to Changing Labor Productivity as a Result of Intensified Heat Stress in a Changing Climate
- Author
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Jinxin Zhu, Dagang Wang, Shuo Wang, and Boen Zhang
- Subjects
labor productivity ,Epidemiology ,adaptation ,Biogeosciences ,Volcanic Effects ,heat stress ,Global Change from Geodesy ,Volcanic Hazards and Risks ,Oceans ,Sea Level Change ,Stochastic Phenomena ,Disaster Risk Analysis and Assessment ,Waste Management and Disposal ,Water Science and Technology ,Global and Planetary Change ,Climate and Interannual Variability ,Overtime ,Subsidy ,Pollution ,Climate Impact ,Earthquake Ground Motions and Engineering Seismology ,Explosive Volcanism ,Earth System Modeling ,Atmospheric Processes ,Probability Distributions, Heavy and Fat‐tailed ,Ocean Monitoring with Geodetic Techniques ,Ocean/Atmosphere Interactions ,Mathematical Geophysics ,Atmospheric ,Regional Modeling ,Downscaling ,Atmospheric Effects ,Volcanology ,Temporal Analysis and Representation ,Management, Monitoring, Policy and Law ,Hydrological Cycles and Budgets ,Decadal Ocean Variability ,Land/Atmosphere Interactions ,Extreme Events ,TD169-171.8 ,Geodesy and Gravity ,Global Change ,Time Series Analysis ,Air/Sea Interactions ,Numerical Modeling ,Solid Earth ,Geological ,Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions ,Water Cycles ,Public Health, Environmental and Occupational Health ,Modeling ,Avalanches ,Volcano Seismology ,Benefit‐cost Analysis ,Space Plasma Physics ,Computational Geophysics ,Regional Climate Change ,Scaling: Spatial and Temporal ,Natural Hazards ,Abrupt/Rapid Climate Change ,Informatics ,Natural resource economics ,Health, Toxicology and Mutagenesis ,Surface Waves and Tides ,Atmospheric Composition and Structure ,Time Series Experiments ,Environmental protection ,dynamical downscaling ,Volcano Monitoring ,uncertainty ,Seismology ,Climatology ,Nonlinear Geophysics ,Radio Oceanography ,Gravity and Isostasy ,Marine Geology and Geophysics ,Physical Modeling ,Oceanography: General ,Air conditioning ,Cryosphere ,Impacts of Global Change ,Oceanography: Physical ,Research Article ,Risk ,Persistence, Memory, Correlations, Clustering ,Oceanic ,Theoretical Modeling ,Climate change ,Radio Science ,Tsunamis and Storm Surges ,Paleoceanography ,Climate Dynamics ,Productivity ,Numerical Solutions ,Sustainable development ,Climate Change and Variability ,Stochastic Processes ,Effusive Volcanism ,business.industry ,Climate Variability ,General Circulation ,Policy Sciences ,Climate Impacts ,Mud Volcanism ,Air/Sea Constituent Fluxes ,Mass Balance ,interval programming model ,Ocean influence of Earth rotation ,Volcano/Climate Interactions ,Environmental science ,Climate model ,Hydrology ,business ,Sea Level: Variations and Mean - Abstract
The intensification of heat stress reduces the labor capacity and hence poses a threat to socio‐economic development. The reliable projection of the changing climate and the development of sound adaptation strategies are thus desired for adapting to the decreasing labor productivity under climate change. In this study, an optimization modeling approach coupled with dynamical downscaling is proposed to design the optimal adaptation strategies for improving labor productivity under heat stress in China. The future changes in heat stress represented by the wet‐bulb globe temperature (WBGT) are projected with a spatial resolution of 25 × 25 km by a regional climate model (RCM) through the dynamical downscaling of its driving global climate model (GCM). Uncertain information such as system costs, environmental costs, and subsidies are also incorporated into the optimization process to provide reliable decision alternatives for improving labor productivity. Results indicate that the intensification of WBGT is overestimated by the GCM compared to the RCM. Such an overestimation can lead to more losses in working hours derived from the GCM than those from the RCM regardless of climate scenarios. Nevertheless, the overestimated heat stress does not alter the regional measures taken to adapt to decreasing labor productivity. Compared to inland regions, the monsoon‐affected regions tend to improve labor productivity by applying air conditioning rather than working overtime due to the cost differences. Consequently, decision‐makers need to optimally make a balance between working overtime and air conditioning measures to meet sustainable development goals., Key Points An optimization model coupled with dynamical downscaling is developed to improve labor productivity under intensified heat stress in ChinaCivilian workers in inland regions will be more vulnerable to the intensified heat stress in a changing climateCompared to the regional climate model, the global climate model overestimates heat stress and thus exaggerates related system costs to recover from the working hour loss
- Published
- 2021
15. Unprecedented Migratory Bird Die‐Off: A Citizen‐Based Analysis on the Spatiotemporal Patterns of Mass Mortality Events in the Western United States
- Author
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Jue Yang, Han Qiu, Rongting Xu, Di Yang, and Anni Yang
- Subjects
Informatics ,Persistence, Memory, Correlations, Clustering ,Epidemiology ,Health, Toxicology and Mutagenesis ,geographically weighted regression ,Winter storm ,Bird migration ,Biodiversity ,Wildlife ,Temporal Analysis and Representation ,Land cover ,Time Series Experiments ,Management, Monitoring, Policy and Law ,Biogeosciences ,Environmental protection ,wildfire ,Extreme weather ,Extreme Events ,extreme weather ,citizen science ,TD169-171.8 ,Stochastic Phenomena ,Time Series Analysis ,Natural disaster ,Waste Management and Disposal ,Water Science and Technology ,Stochastic Processes ,Global and Planetary Change ,Nonlinear Geophysics ,Ecology ,Public Health, Environmental and Occupational Health ,Geohealth ,Pollution ,Oceanography: General ,Impacts of Climate Change: Ecosystem Health ,Life in Extreme Environments ,Habitat ,Probability Distributions, Heavy and Fat‐tailed ,Space Plasma Physics ,Hydrology ,Scaling: Spatial and Temporal ,Mathematical Geophysics ,Natural Hazards ,Research Article ,bird mortality - Abstract
Extensive, severe wildfires, and wildfire‐induced smoke occurred across the western and central United States since August 2020. Wildfires resulting in the loss of habitats and emission of particulate matter and volatile organic compounds pose serious threatens to wildlife and human populations, especially for avian species, the respiratory system of which are sensitive to air pollutions. At the same time, the extreme weather (e.g., snowstorms) in late summer may also impact bird migration by cutting off their food supply and promoting their migration before they were physiologically ready. In this study, we investigated the environmental drivers of massive bird die‐offs by combining socioecological earth observations data sets with citizen science observations. We employed the geographically weighted regression models to quantitatively evaluate the effects of different environmental and climatic drivers, including wildfire, air quality, extreme weather, drought, and land cover types, on the spatial pattern of migratory bird mortality across the western and central US during August‐September 2020. We found that these drivers affected the death of migratory birds in different ways, among which air quality and distance to wildfire were two major drivers. Additionally, there were more bird mortality events found in urban areas and close to wildfire in early August. However, fewer bird deaths were detected closer to wildfires in California in late August and September. Our findings highlight the important impact of extreme weather and natural disasters on bird biology, survival, and migration, which can provide significant insights into bird biodiversity, conservation, and ecosystem sustainability., Key Points We investigated the environmental drivers of massive bird die‐offs by combining earth observations with citizen science observationsWe found distance to wildfire and air quality were the major factors that affect the birth mortality eventsOur findings highlight the important impact of extreme weather and natural disasters on bird biology, survival, and migration
- Published
- 2021
16. Dynamic regimes of the stochastic 'prey - predatory' model with competition and saturation
- Author
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Tatyana Ryazanova and Ekaterina Pavlovna Abramova
- Subjects
Physics ,Bistability ,bistability ,media_common.quotation_subject ,lcsh:T57-57.97 ,lcsh:Mathematics ,Mechanics ,STOCHASTIC PHENOMENA ,lcsh:QA1-939 ,Competition (biology) ,Computer Science Applications ,Predation ,POPULATION DYNAMICS ,Computational Theory and Mathematics ,BISTABILITY ,Modeling and Simulation ,lcsh:Applied mathematics. Quantitative methods ,population dynamics ,stochastic phenomena ,Quantitative Biology::Populations and Evolution ,Saturation (chemistry) ,media_common - Abstract
We consider “predator – prey” model taking into account the competition of prey, predator for different from the prey resources, and their interaction described by the second type Holling trophic function. An analysis of the attractors is carried out depending on the coefficient of competition of predators. In the deterministic case, this model demonstrates the complex behavior associated with the local (Andronov – Hopf and saddle-node) and global (birth of a cycle from a separatrix loop) bifurcations. An important feature of this model is the disappearance of a stable cycle due to a saddle-node bifurcation. As a result of the presence of competition in both populations, parametric zones of mono- and bistability are observed. In parametric zones of bistability the system has either coexisting two equilibria or a cycle and equilibrium. Here, we investigate the geometrical arrangement of attractors and separatrices, which is the boundary of basins of attraction. Such a study is an important component in understanding of stochastic phenomena. In this model, the combination of the nonlinearity and random perturbations leads to the appearance of new phenomena with no analogues in the deterministic case, such as noise-induced transitions through the separatrix, stochastic excitability, and generation of mixed-mode oscillations. For the parametric study of these phenomena, we use the stochastic sensitivity function technique and the confidence domain method. In the bistability zones, we study the deformations of the equilibrium or oscillation regimes under stochastic perturbation. The geometric criterion for the occurrence of such qualitative changes is the intersection of confidence domains and the separatrix of the deterministic model. In the zone of monostability, we evolve the phenomena of explosive change in the size of population as well as extinction of one or both populations with minor changes in external conditions. With the help of the confidence domains method, we solve the problem of estimating the proximity of a stochastic population to dangerous boundaries, upon reaching which the coexistence of populations is destroyed and their extinction is observed. c 2019 Ekaterina P. Abramova, Tatyana V. Ryazanova. Russian Science Foundation, RSF: 16-11-10098 This work was supported by Russian Science Foundation (No. 16-11-10098).
- Published
- 2019
17. Vb Cyclones Synchronized With the Arctic‐/North Atlantic Oscillation
- Author
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M. Hofstätter and Günter Blöschl
- Subjects
Western Mediterranean ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,02 engineering and technology ,01 natural sciences ,Oceans ,Earth and Planetary Sciences (miscellaneous) ,Stochastic Phenomena ,020701 environmental engineering ,Research Articles ,Climatology ,teleconnection ,Climate and Dynamics ,Climate and Interannual Variability ,Synoptic‐scale Meteorology ,Vb track ,Jet stream ,Oceanography: General ,mid latitude cyclones ,climate change ,Geophysics ,Atmospheric Processes ,Cyclone ,Ocean Monitoring with Geodetic Techniques ,Mathematical Geophysics ,Fronts and Jets ,Geology ,Oceanography: Physical ,Research Article ,clustering ,Persistence, Memory, Correlations, Clustering ,Atmospheric circulation ,0207 environmental engineering ,Climate change ,Hiatus ,Decadal Ocean Variability ,Extreme Events ,Geodesy and Gravity ,Global Change ,0105 earth and related environmental sciences ,Climate Change and Variability ,Stochastic Processes ,Climate Variability ,General Circulation ,Mass Balance ,Arctic oscillation ,13. Climate action ,Space and Planetary Science ,North Atlantic oscillation ,Space Plasma Physics ,Natural Hazards ,Teleconnection - Abstract
Vb cyclones typically emerge in the Western Mediterranean and propagate to the Northeast into Central Europe. This paper explores the temporal characteristics of Vb cyclone occurrence based on cyclone tracks identified at the atmospheric levels of Z700 and sea level pressure, using JRA‐55 reanalysis data for the period 1959–2015. The risk of Vb occurrence was significantly high in the 1960s and has remained at a lower level since then. Vb cyclones do not occur fully randomly according to a Poisson point process. Eleven well‐separated and distinct clusters as well as 11 hiatus periods are identified, with average occurrence rates of 21.5 and 5.2 yrea−1, respectively. During the event of Vb, the large‐scale atmospheric circulation is changed into a state favoring the development of successive Vb cyclones. Clustering is very prominent in the case of Genoan Vb cyclones in summer as well as those Vb cyclones developing over the Iberian Peninsula or the North African Coast in winter. Superposition of the polar and the subtropical jet stream over the Western Mediterranean is identified as a main feature at the onset of Vb cyclones. Vb cyclone occurrence appears to be synchronized with the Northern Atlantic Oscillation (NAO; at Z500) and Arctic Oscillation (AO; at Z1000). Clusters have occurred when both NAO and AO were negative. This relation applies to Western Mediterranean cyclones not following a Vb track as well, however to a much weaker extent. In contrast, Vb cyclone frequency was particularly low from 1988 to 1997 during a sustained positive phase of both NAO and AO., Key Points In the past 50 years, the frequency of Vb cyclones was high in the 1960s and lower since thenVb cyclones were strongly synchronized with NAO and AO; high frequency clusters occurred when NAO and AO were negativeThe coupling of the polar and the subtropical jet stream over the Western Mediterranean is a driving mechanism of the onset of Vb cyclones
- Published
- 2019
18. Stochastic phenomena in pattern formation for distributed nonlinear systems
- Abstract
We study a stochastic spatially extended population model with diffusion, where we find the coexistence of multiple non-homogeneous spatial structures in the areas of Turing instability. Transient processes of pattern generation are studied in detail. We also investigate the influence of random perturbations on the pattern formation. Scenarios of noise-induced pattern generation and stochastic transformations are studied using numerical simulations and modality analysis. © 2020 The Author(s) Published by the Royal Society. All rights reserved.
- Published
- 2020
19. Shifting Patterns of Summer Lake Color Phenology in Over 26,000 US Lakes
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S. Topp, Xiao Yang, Hilary A. Dugan, Matthew R. V. Ross, John R. Gardner, and Tamlin M. Pavelsky
- Subjects
Space Geodetic Surveys ,Informatics ,010504 meteorology & atmospheric sciences ,Limnology ,0208 environmental biotechnology ,Drainage basin ,02 engineering and technology ,Time Series Experiments ,Biogeosciences ,01 natural sciences ,Population density ,Biogeochemical Kinetics and Reaction Modeling ,Remote Sensing ,Oceanography: Biological and Chemical ,Phytoplankton succession ,big data ,lakes ,Stochastic Phenomena ,Water Science and Technology ,geography.geographical_feature_category ,Phenology ,Nonlinear Geophysics ,Remote Sensing and Disasters ,Biogeochemistry ,Oceanography: General ,Atmospheric Processes ,Probability Distributions, Heavy and Fat‐tailed ,ecology ,Cryosphere ,Biogeochemical Cycles, Processes, and Modeling ,Mathematical Geophysics ,Research Article ,Persistence, Memory, Correlations, Clustering ,Volcanology ,Temporal Analysis and Representation ,phenology ,Paleoceanography ,Extreme Events ,medicine ,Remote Sensing of Volcanoes ,Geodesy and Gravity ,Global Change ,Time Series Analysis ,Data Assimilation, Integration and Fusion ,0105 earth and related environmental sciences ,geography ,Stochastic Processes ,Lake ecosystem ,Seasonality ,medicine.disease ,020801 environmental engineering ,Environmental science ,Space Plasma Physics ,Physical geography ,Hydrology ,Scale (map) ,Scaling: Spatial and Temporal ,Natural Hazards - Abstract
Lakes are often defined by seasonal cycles. The seasonal timing, or phenology, of many lake processes are changing in response to human activities. However, long‐term records exist for few lakes, and extrapolating patterns observed in these lakes to entire landscapes is exceedingly difficult using the limited number of available in situ observations. Limited landscape‐level observations mean we do not know how common shifts in lake phenology are at macroscales. Here, we use a new remote sensing data set, LimnoSat‐US, to analyze U.S. summer lake color phenology between 1984 and 2020 across more than 26,000 lakes. Our results show that summer lake color seasonality can be generalized into five distinct phenology groups that follow well‐known patterns of phytoplankton succession. The frequency with which lakes transition from one phenology group to another is tied to lake and landscape level characteristics. Lakes with high inflows and low variation in their seasonal surface area are generally more stable, while lakes in areas with high interannual variations in climate and catchment population density show less stability. Our results reveal previously unexamined spatiotemporal patterns in lake seasonality and demonstrate the utility of LimnoSat‐US, which, with over 22 million remote sensing observations of lakes, creates novel opportunities to examine changing lake ecosystems at a national scale., Key Points Summer lake color phenology can be generalized into five distinct seasonal patterns of greening and blueing eventsSince the mid‐1990s, the number of lakes with color patterns corresponding to eutrophic waterbodies has been increasingWe observe these patterns using a new U.S. lake remote sensing data set that contains over 22 million lake observations
- Published
- 2020
20. Tumor growth modeling via Fokker–Planck equation.
- Author
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Heidari, Hossein, Karamati, Mahdi Rezaei, and Motavalli, Hossein
- Subjects
- *
FOKKER-Planck equation , *TUMOR growth , *PROBABILITY density function , *OLDER women , *CANCER radiotherapy - Abstract
In the present investigation, a stochastic tumor growth model is presented based on the Morse potential. The solution of the Fokker–Planck equation is used to study the growth rate and the geometry of breast cancer with and without radiation therapy effects. In the second case, to estimate unknown parameters of the probability density function, breast data from the Surveillance, Epidemiology, and End Results program and machine learning algorithm are used. By considering three groups of women (35–85 years old), the results show that as time goes on, tumor size increases while its growth rate decreases, and the older women have a slower growth rate. Also, the simulation results of breast tumors of mice confirm that our results are consistent with the experimental evidence in both cases of radiotherapy and no treatment. Finally, the finding of this study implies that the present model is accurate than the Gompertz one in predicting tumor size, in the treatment case. • The time-dependent Fokker–Planck equation is solved for Morse potential. • The PDF of the tumor size is estimated by using experimental data and a machine learning algorithm. • The PDF of the tumor size is used to estimate the breast tumor boundary and its growth rate with and without therapy. • As time goes on, tumor size increases while its growth rate decreases, and older women have a slower growth rate. • The finding of this study implies that the present model is accurate than the Gompertz one in the treatment case. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
21. A reconstruction algorithm for temporally aliased seismic signals recorded by the InSight Mars lander
- Author
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Nienke Brinkman, Martin van Driel, Sharon Kedar, Raphaël F. Garcia, Johan O. A. Robertsson, Fredrik Andersson, Cedric Schmelzbach, John Clinton, Philippe Lognonné, Simon Stähler, Thomas Haag, Tilman Spohn, David Sollberger, William B. Banerdt, Matthias Grott, William T. Pike, Troy L. Hudson, Domenico Giardini, Peter Zweifel, Jan ten Pierick, and Institut Supérieur de l'Aéronautique et de l'Espace - ISAE-SUPAERO (FRANCE)
- Subjects
Informatics ,Astronomy ,aliasing ,Time Series Experiments ,Signal ,Planetary Sciences: Solar System Objects ,Sampling (signal processing) ,Aliasing ,Stochastic Phenomena ,Traitement du signal et de l'image ,signal reconstruction ,Instruments and Techniques ,QE1-996.5 ,Exploration Geophysics ,Nonlinear Geophysics ,Mars landing ,Geology ,Reconstruction algorithm ,Mars Exploration Program ,Oceanography: General ,Probability Distributions, Heavy and Fat‐tailed ,Planetary Sciences: Comets and Small Bodies ,Mathematical Geophysics ,Research Article ,Seismometer ,Persistence, Memory, Correlations, Clustering ,Acoustics ,Mars ,QB1-991 ,Temporal Analysis and Representation ,seismic exploration ,Environmental Science (miscellaneous) ,Extreme Events ,Time Series Analysis ,signal processing ,Planetary Sciences: Solid Surface Planets ,Planetary Sciences: Fluid Planets ,Mars seismic data analysis ,Stochastic Processes ,Computational Methods: Seismic ,Interiors ,InSight at Mars ,Tectonophysics ,General Earth and Planetary Sciences ,Space Plasma Physics ,Nyquist frequency ,Hydrology ,Scaling: Spatial and Temporal ,InSight Mars Geophysics Regolith HP3 SEIS ,Natural Hazards ,Planetary Interiors - Abstract
In December 2018, the NASA InSight lander successfully placed a seismometer on the surface of Mars. Alongside, a hammering device was deployed at the landing site that penetrated into the ground to attempt the first measurements of the planetary heat flow of Mars. The hammering of the heat probe generated repeated seismic signals that were registered by the seismometer and can potentially be used to image the shallow subsurface just below the lander. However, the broad frequency content of the seismic signals generated by the hammering extends beyond the Nyquist frequency governed by the seismometer's sampling rate of 100 samples per second. Here, we propose an algorithm to reconstruct the seismic signals beyond the classical sampling limits. We exploit the structure in the data due to thousands of repeated, only gradually varying hammering signals as the heat probe slowly penetrates into the ground. In addition, we make use of the fact that repeated hammering signals are sub-sampled differently due to the unsynchronized timing between the hammer strikes and the seismometer recordings. This allows us to reconstruct signals beyond the classical Nyquist frequency limit by enforcing a sparsity constraint on the signal in a modified Radon transform domain. In addition, the proposed method reduces uncorrelated noise in the recorded data. Using both synthetic data and actual data recorded on Mars, we show how the proposed algorithm can be used to reconstruct the high-frequency hammering signal at very high resolution., Earth and Space Science, 8 (8), ISSN:2333-5084
- Published
- 2020
22. Stochastic phenomena in pattern formation for distributed nonlinear systems
- Author
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Alexander Kolinichenko, Lev Ryashko, and Alexander N. Pisarchik
- Subjects
PATTERN FORMATION ,COMPUTER SIMULATION ,General Mathematics ,STOCHASTIC MODEL ,General Physics and Astronomy ,Pattern formation ,STOCHASTIC PHENOMENA ,01 natural sciences ,Noise (electronics) ,TURING INSTABILITY ,010305 fluids & plasmas ,NOISE ,Diffusion ,Turing instability ,0103 physical sciences ,NONLINEAR SYSTEM ,Statistical physics ,Diffusion (business) ,ARTICLE ,010306 general physics ,Physics ,Self-organization ,Stochastic Processes ,BODY PATTERNING ,General Engineering ,Articles ,RANDOM PERTURBATIONS ,SELF-ORGANIZATION ,STOCHASTIC SYSTEMS ,DIFFUSION ,Nonlinear system ,POPULATION DYNAMICS ,Population model ,Nonlinear Dynamics ,STOCHASTIC MODELS ,PATTERN GENERATION ,TRANSIENT PROCESS ,Transient (oscillation) ,MODALITY ANALYSIS ,SPATIAL STRUCTURE - Abstract
We study a stochastic spatially extended population model with diffusion, where we find the coexistence of multiple non-homogeneous spatial structures in the areas of Turing instability. Transient processes of pattern generation are studied in detail. We also investigate the influence of random perturbations on the pattern formation. Scenarios of noise-induced pattern generation and stochastic transformations are studied using numerical simulations and modality analysis. © 2020 The Author(s) Published by the Royal Society. All rights reserved. Russian Science Foundation, RSF: 16-11-10098 Data accessibility. This article has no additional data. Authors’ contributions. All authors contributed equally. Competing interests. We declare we have no competing interests. Funding. The work was supported by the Russian Science Foundation (grant no. 16-11-10098).
- Published
- 2020
23. The impact of a stochastic parameterization scheme on climate sensitivity in EC‐Earth
- Author
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Peter A. G. Watson, Tim Palmer, and Kristian Strommen
- Subjects
Global Climate Models ,Atmospheric Science ,Persistence, Memory, Correlations, Clustering ,010504 meteorology & atmospheric sciences ,Cloud cover ,Cloud computing ,Forcing (mathematics) ,01 natural sciences ,Decadal Ocean Variability ,Paleoceanography ,Oceans ,Earth and Planetary Sciences (miscellaneous) ,Stochastic Phenomena ,Subgrid-scale (SGS) parameterization ,Global Change ,Research Articles ,Physics::Atmospheric and Oceanic Physics ,0105 earth and related environmental sciences ,Climate Change and Variability ,Climatology ,Stochastic Processes ,Global temperature ,business.industry ,Nonlinear Geophysics ,Climate Variability ,Global warming ,Climate and Dynamics ,Climate and Interannual Variability ,Probability Distributions, Heavy and Fat-Tailed ,Term (time) ,Oceanography: General ,Geophysics ,13. Climate action ,Space and Planetary Science ,Atmospheric Processes ,Climate sensitivity ,Space Plasma Physics ,Climate model ,business ,Scaling: Spatial and Temporal ,Mathematical Geophysics ,Oceanography: Physical ,Research Article - Abstract
Stochastic schemes, designed to represent unresolved subgrid‐scale variability, are frequently used in short and medium‐range weather forecasts, where they are found to improve several aspects of the model. In recent years, the impact of stochastic physics has also been found to be beneficial for the model's long‐term climate. In this paper, we demonstrate for the first time that the inclusion of a stochastic physics scheme can notably affect a model's projection of global warming, as well as its historical climatological global temperature. Specifically, we find that when including the “stochastically perturbed parametrization tendencies” (SPPT) scheme in the fully coupled climate model EC‐Earth v3.1, the predicted level of global warming between 1850 and 2100 is reduced by 10% under an RCP8.5 forcing scenario. We link this reduction in climate sensitivity to a change in the cloud feedbacks with SPPT. In particular, the scheme appears to reduce the positive low cloud cover feedback and increase the negative cloud optical feedback. A key role is played by a robust, rapid increase in cloud liquid water with SPPT, which we speculate is due to the scheme's nonlinear interaction with condensation., Key Points The inclusion of a stochastic scheme reduces climate sensitivity in a general circulation modelThis reduction, of around 10%, is linked to changes in cloud cover and cloud optical depth feedbacksWell‐calibrated stochastic schemes may give more accurate global warming projections
- Published
- 2019
24. Dynamic regimes of the stochastic “prey – predatory” model with competition and saturation
- Abstract
We consider “predator – prey” model taking into account the competition of prey, predator for different from the prey resources, and their interaction described by the second type Holling trophic function. An analysis of the attractors is carried out depending on the coefficient of competition of predators. In the deterministic case, this model demonstrates the complex behavior associated with the local (Andronov – Hopf and saddle-node) and global (birth of a cycle from a separatrix loop) bifurcations. An important feature of this model is the disappearance of a stable cycle due to a saddle-node bifurcation. As a result of the presence of competition in both populations, parametric zones of mono- and bistability are observed. In parametric zones of bistability the system has either coexisting two equilibria or a cycle and equilibrium. Here, we investigate the geometrical arrangement of attractors and separatrices, which is the boundary of basins of attraction. Such a study is an important component in understanding of stochastic phenomena. In this model, the combination of the nonlinearity and random perturbations leads to the appearance of new phenomena with no analogues in the deterministic case, such as noise-induced transitions through the separatrix, stochastic excitability, and generation of mixed-mode oscillations. For the parametric study of these phenomena, we use the stochastic sensitivity function technique and the confidence domain method. In the bistability zones, we study the deformations of the equilibrium or oscillation regimes under stochastic perturbation. The geometric criterion for the occurrence of such qualitative changes is the intersection of confidence domains and the separatrix of the deterministic model. In the zone of monostability, we evolve the phenomena of explosive change in the size of population as well as extinction of one or both populations with minor changes in external conditions. With the help of the confidence domains method
- Published
- 2019
25. THE STOCHASTIC RESETTING AND MASTER NONLINEAR FOKKER-PLANCK IN DISCRETE SPECTROSCOPY OF ULTRATHIN SILICON DIOXIDE FILM.
- Author
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BAHARI, ALI
- Subjects
- *
SPECTRUM analysis , *SILICA films , *CONSTRAINTS (Physics) , *NONLINEAR theories , *FOKKER-Planck equation , *SYNCHROTRON radiation , *FLUCTUATIONS (Physics) , *STOCHASTIC processes - Abstract
In this paper, we consider a particle (carrier) which is stochastically reset to its initial position at a constant rate r. It leads toward a non-equilibrium stationary state with non-Gaussian fluctuations for the particle position and enhance escape rate of particles through the ultrathin film. Here we explore strongly-correlated random sequences. It is based on Master - nonlinear Fokker-Planck and chemical reaction equations. In that case compounding moments can set useful constraints to synchrotron radiation spectra of ultrathin film (SRSUTF). This mechanism is explained within a fitting process where both diffusion and reaction occur in discrete cells, and with both Si and O2 treated as moving and reacting species for the very thin oxides. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
26. OPTIMAL DIRECTED CURRENT OF A BROWNIAN MOTOR UNDER A NON-GAUSSIAN NOISE GENERATED BY A MULTIPLICATIVE PROCESS.
- Author
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DUARTE, J. R. R. and LYRA, M. L.
- Subjects
- *
DISTRIBUTION (Probability theory) , *GAUSSIAN distribution , *NOISE generators (Electronics) , *RANDOM noise theory , *PROBABILITY theory - Abstract
Unidirectional motion is achieved when a particle, moving under the influence of an underlying noise source, is subjected to a ratchet asymmetric periodic potential. Here, we investigate how deviations from the Gaussian nature of the noise distribution function impacts the average particle's current. The input noise is considered to be produced by a Langevin process including both multiplicative and additive random noise sources. The resulting input random signal has a power-law amplitude distribution and a finite correlation time. These features are controlled by the average of the multiplicative noise. We show that the average particle's velocity depends non-monotonically on the degree of non-Gaussianity of the input noise. It exhibits a maximum at an intermediate value of the effective power-law exponent that characterizes the asymptotic decay of the noise probability distribution function. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
27. Thermodynamic constraints on stochastic acceleration in compressional turbulence.
- Author
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Fisk, Lennard A. and Gioeckler, George
- Subjects
- *
THERMODYNAMICS , *PARTICLE acceleration , *TURBULENCE , *SOLAR wind , *CONSTRAINTS (Physics) , *SPACE plasmas , *STOCHASTIC processes - Abstract
Recent observations in the solar wind have revealed an important phenomenon. In circumstances where stochastic acceleration is expected, a suprathermal tail on the distribution function is formed with a common spectral shape: the spectrum is a power law in particle speed with a spectral index of -5. This common spectrum occurs in the quiet solar wind; in disturbed conditions downstream from shocks; and, in particular, throughout the heliosheath downstream from the termination shock of the solar wind currently being explored by Voyager 1. In this article, simple thermodynamic principles are applied to stochastic acceleration in compressional turbulence. The unique spectral index results when the entropy of the suprathermal tail has increased to the maximum allowable value. Relationships for the pressure in the suprathermal tail are also derived and found to be in agreement with observations. The results are shown to be consistent with the suprathermal tail arising from a cascade in energy, analogous to a turbulent cascade. The results may be applied broadly, because stochastic acceleration in compressional turbulence should be common in many astrophysical settings. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
28. Modelling of the behaviour of the cell–wall interface during the rolling of a single cell: a probabilistic approach
- Author
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Mefti, Nacim, Haussy, Bernard, and François Ganghoffer, Jean
- Subjects
- *
CELL adhesion , *LEUCOCYTES , *MOLECULES , *SIMULATION methods & models , *ADHESION - Abstract
Abstract: Rolling is an important manifestation of biological cell adhesion, especially for the leukocyte cell in the immune process. It combines several phenomena such as the affinity, the junction and failure between a specific adhesion molecules and an active deformation of the cell during the motility. Several models were developed in a probabilistic or a deterministic context. The focus in this Note is the local mechanical description (2D) of the kinetic of adhesion of the contact interface of a single cell with a wall (e.g., the blood vein), in terms of the failure and creation of connections during the rolling. The local model focuses on the interfacial zone, as a preliminary step towards an integrated model including the cell membrane behavior. Hence, the net effect of the fluid flow is represented by a punctual force, coupled to the Van der Waals and electrostatic forces. Note that the complexity of this phenomenon leads to the limitation of the number of parameters, which are taken into account in the model. Numerical simulations emphasize the rolling phenomenon and the kinetics of creation and rupture of the ligands–receptors connections. To cite this article: N. Mefti et al., C. R. Mecanique 334 (2006). [Copyright &y& Elsevier]
- Published
- 2006
- Full Text
- View/download PDF
29. Scaling Properties of Arctic Sea Ice Deformation in a High-Resolution Viscous-Plastic Sea Ice Model and in Satellite Observations
- Author
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Nils Hutter, Martin Losch, and Dimitris Menemenlis
- Subjects
Leads ,Informatics ,010504 meteorology & atmospheric sciences ,Time Series Experiments ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,law.invention ,law ,Arctic Ocean ,Earth and Planetary Sciences (miscellaneous) ,Stochastic Phenomena ,Temporal scales ,Research Articles ,Physics::Atmospheric and Oceanic Physics ,geography.geographical_feature_category ,Nonlinear Geophysics ,Sea Ice ,scaling ,sea ice rheology ,Geodesy ,Physical Modeling ,Dynamics ,Oceanography: General ,Geophysics ,Cryosphere ,Mathematical Geophysics ,Geology ,Oceanography: Physical ,Research Article ,sea ice deformation ,Temporal Analysis and Representation ,Deformation (meteorology) ,Physics::Geophysics ,Ice Mechanics and Air/Sea/Ice Exchange Processes ,Geochemistry and Petrology ,Intermittency ,Sea ice ,14. Life underwater ,Time Series Analysis ,Scaling ,0105 earth and related environmental sciences ,Stochastic Processes ,geography ,Modeling ,Arctic ice pack ,Arctic ,13. Climate action ,Space and Planetary Science ,high‐resolution modeling ,Space Plasma Physics ,Satellite ,Hydrology ,Scaling: Spatial and Temporal ,Natural Hazards - Abstract
Sea ice models with the traditional viscous‐plastic (VP) rheology and very small horizontal grid spacing can resolve leads and deformation rates localized along Linear Kinematic Features (LKF). In a 1 km pan‐Arctic sea ice‐ocean simulation, the small‐scale sea ice deformations are evaluated with a scaling analysis in relation to satellite observations of the Envisat Geophysical Processor System (EGPS) in the Central Arctic. A new coupled scaling analysis for data on Eulerian grids is used to determine the spatial and temporal scaling and the coupling between temporal and spatial scales. The spatial scaling of the modeled sea ice deformation implies multifractality. It is also coupled to temporal scales and varies realistically by region and season. The agreement of the spatial scaling with satellite observations challenges previous results with VP models at coarser resolution, which did not reproduce the observed scaling. The temporal scaling analysis shows that the VP model, as configured in this 1 km simulation, does not fully resolve the intermittency of sea ice deformation that is observed in satellite data., Key Points Sea ice deformation localizes along lines in high‐resolution viscous‐plastic sea ice modelsThe model reproduces spatial scaling properties also observed in satellite dataThe model underestimates temporal scaling compared to satellite data
- Published
- 2018
30. Динамические режимы модели связанных логистических осцилляторов с аддитивным шумом
- Abstract
The coupled-logistic map that is used in cryptographic algorithms for data transmission is discussed. Different regimes and bifurcations caused by changing coupling parameters are studied. The change of the zones of guaranteed chaos under the influence of external random influence on the system is investigated., В работе изучается модель связанных логистических осцилляторов, используемая в криптографических алгоритмах передачи информации. Рассматриваются различные режимы и бифуркации, вызванные изменением параметров связи. Исследуется изменение зон гарантированного хаоса при воздействии на систему внешнего случайного воздействия.
- Published
- 2017
31. Stochastic phenomena in a fiber Raman amplifier
- Abstract
The interplay of such cornerstones of modern nonlinear fiber optics as a nonlinearity, stochasticity and polarization leads to variety of the noise induced instabilities including polarization attraction and escape phenomena harnessing of which is a key to unlocking the fiber optic systems specifications required in high resolution spectroscopy, metrology, biomedicine and telecommunications. Here, by using direct stochastic modeling, the mapping of interplay of the Raman scattering-based nonlinearity, the random birefringence of a fiber, and the pump-to-signal intensity noise transfer has been done in terms of the fiber Raman amplifier parameters, namely polarization mode dispersion, the relative intensity noise of the pump laser, fiber length, and the signal power. The obtained results reveal conditions for emergence of the random birefringence-induced resonance-like enhancement of the gain fluctuations (stochastic anti-resonance) accompanied by pulse broadening and rare events in the form of low power output signals having probability heavily deviated from the Gaussian distribution. (Figure presented.). © 2016 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, QC 20201002
- Published
- 2017
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- View/download PDF
32. Annular modes and apparent eddy feedbacks in the Southern Hemisphere
- Author
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Nicholas J, Byrne, Theodore G, Shepherd, Tim, Woollings, and R Alan, Plumb
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Informatics ,Persistence, Memory, Correlations, Clustering ,annular modes ,Climate ,Temporal Analysis and Representation ,Time Series Experiments ,nonstationary interannual variability ,Physics::Geophysics ,Decadal Ocean Variability ,Extreme Events ,Oceans ,Research Letter ,Stochastic Phenomena ,Global Change ,Time Series Analysis ,Physics::Atmospheric and Oceanic Physics ,Stratosphere/Troposphere Interactions ,Climate Change and Variability ,Climatology ,Stochastic Processes ,Nonlinear Geophysics ,Climate Variability ,Climate and Interannual Variability ,Research Letters ,lagged correlation analysis ,Oceanography: General ,Atmospheric Processes ,Space Plasma Physics ,eddy feedbacks ,Hydrology ,Scaling: Spatial and Temporal ,Mathematical Geophysics ,Natural Hazards ,Oceanography: Physical - Abstract
Lagged correlation analysis is often used to infer intraseasonal dynamical effects but is known to be affected by nonstationarity. We highlight a pronounced quasi 2 year peak in the anomalous zonal wind and eddy momentum flux convergence power spectra in the Southern Hemisphere, which is prima facie evidence for nonstationarity. We then investigate the consequences of this nonstationarity for the Southern Annular Mode and for eddy momentum flux convergence. We argue that positive lagged correlations previously attributed to the existence of an eddy feedback are more plausibly attributed to nonstationary interannual variability external to any potential feedback process in the midlatitude troposphere. The findings have implications for the diagnosis of feedbacks in both models and reanalysis data as well as for understanding the mechanisms underlying variations in the zonal wind., Key Points Analysis of lagged correlations between Southern Annular Mode and eddy momentum flux convergence in reanalysis dataPrevious evidence for an eddy feedback more plausibly interpreted as nonstationary interannual variabilitySouthern Annular Mode and eddy momentum flux convergence power spectra exhibit a pronounced quasi 2 year peak
- Published
- 2015
33. Students’ Reasoning About One-Object Stochastic Phenomena in an ICT-Environment
- Author
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Iversen, Kjærand and Nilsson, Per
- Published
- 2007
- Full Text
- View/download PDF
34. Probabilistic features of lifetime in fatigue. Influence of flows [Aspects probabilistes de la durée de vie en fatigue Influence des défauts]
- Author
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Lamon, J., Laboratoire de Mécanique et Technologie (LMT), and École normale supérieure - Cachan (ENS Cachan)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Microstructural defects ,Fracture of composites ,Slow crack growth ,Statistical distribution ,Stochastic phenomena ,Stress concentrators ,Reinforcement ,[SPI.MAT]Engineering Sciences [physics]/Materials ,Fibers ,Stochastic models ,Fracture ,Probability distributions ,Multi-scale approaches ,Stress concentration ,Fatigue of materials ,Lifetime ,Ceramic matrix composites - Abstract
cited By 0; International audience; The fracture of fibres dictates the fracture of composites reinforced by long fibres. The ceramic matrix composites that are made of a ceramic matrix reinforced by ceramic fibres, display features that are interesting to address lifetime issues. The flaws they contain have a random distribution, and act as stress concentrators. The resistances to failure display a statistical distribution. The effects of microstructural defects on lifetime are discussed in the present paper. A multi scale approach based on modelling of the damage modes in the matrix and the fibers is outlined. The models integrate facture probabilities owing to stochastic phenomena induced by the statistical distribution of microstructural flaws. © 2013 Lavoisier.
- Published
- 2013
35. Origins of stochastic intracellular processes and consequences for cell-to-cell variability and cellular survival strategies
- Author
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Schwabe, Anne, Dobrzynski, Maciej, Rybakova, K.N., Verschure, P.J., Bruggeman, Frank, Jameson, D, Westerhoff, Hans, and Evolutionary Intelligence
- Subjects
cell biology ,stochastic phenomena ,systems biology ,transcription - Abstract
Quantitative analyses of the dynamics of single cells have become a powerful approach in current cell biology. They give us an unprecedented opportunity to study dynamics of molecular networks at a high level of accuracy in living single cells. Genetically identical cells, growing in the same environment and sharing the same growth history, can differ remarkably in their molecular makeup and physiological behaviors. The origins of this cell-to-cell variability have in many cases been traced to the inevitable stochasticity of molecular reactions. Those mechanisms can cause isogenic cells to have qualitatively different life histories. Many studies indicate that molecular noise can be exploited by cell populations to enhance survival prospects in uncertain environments. On the other hand, cells have evolved noise-suppression mechanisms to cope with the inevitable noise in their functioning so as to reduce the hazardous effects of noise. In this chapter, we discuss key experiments, theoretical results, and physiological consequences of molecular stochasticity to introduce this exciting field to a broader community of (systems) biologists.
- Published
- 2011
36. Origins of stochastic intracellular processes and consequences for cell-to-cell variability and cellular survival strategies
- Subjects
cell biology ,stochastic phenomena ,systems biology ,transcription - Abstract
Quantitative analyses of the dynamics of single cells have become a powerful approach in current cell biology. They give us an unprecedented opportunity to study dynamics of molecular networks at a high level of accuracy in living single cells. Genetically identical cells, growing in the same environment and sharing the same growth history, can differ remarkably in their molecular makeup and physiological behaviors. The origins of this cell-to-cell variability have in many cases been traced to the inevitable stochasticity of molecular reactions. Those mechanisms can cause isogenic cells to have qualitatively different life histories. Many studies indicate that molecular noise can be exploited by cell populations to enhance survival prospects in uncertain environments. On the other hand, cells have evolved noise-suppression mechanisms to cope with the inevitable noise in their functioning so as to reduce the hazardous effects of noise. In this chapter, we discuss key experiments, theoretical results, and physiological consequences of molecular stochasticity to introduce this exciting field to a broader community of (systems) biologists.
- Published
- 2011
37. Origins of stochastic intracellular processes and consequences for cell-to-cell variability and cellular survival strategies.
- Abstract
Quantitative analyses of the dynamics of single cells have become a powerful approach in current cell biology. They give us an unprecedented opportunity to study dynamics of molecular networks at a high level of accuracy in living single cells. Genetically identical cells, growing in the same environment and sharing the same growth history, can differ remarkably in their molecular makeup and physiological behaviors. The origins of this cell-to-cell variability have in many cases been traced to the inevitable stochasticity of molecular reactions. Those mechanisms can cause isogenic cells to have qualitatively different life histories. Many studies indicate that molecular noise can be exploited by cell populations to enhance survival prospects in uncertain environments. On the other hand, cells have evolved noise-suppression mechanisms to cope with the inevitable noise in their functioning so as to reduce the hazardous effects of noise. In this chapter, we discuss key experiments, theoretical results, and physiological consequences of molecular stochasticity to introduce this exciting field to a broader community of (systems) biologists.
- Published
- 2011
38. Origins of stochastic intracellular processes and consequences for cell-to-cell variability and cellular survival strategies.
- Abstract
Quantitative analyses of the dynamics of single cells have become a powerful approach in current cell biology. They give us an unprecedented opportunity to study dynamics of molecular networks at a high level of accuracy in living single cells. Genetically identical cells, growing in the same environment and sharing the same growth history, can differ remarkably in their molecular makeup and physiological behaviors. The origins of this cell-to-cell variability have in many cases been traced to the inevitable stochasticity of molecular reactions. Those mechanisms can cause isogenic cells to have qualitatively different life histories. Many studies indicate that molecular noise can be exploited by cell populations to enhance survival prospects in uncertain environments. On the other hand, cells have evolved noise-suppression mechanisms to cope with the inevitable noise in their functioning so as to reduce the hazardous effects of noise. In this chapter, we discuss key experiments, theoretical results, and physiological consequences of molecular stochasticity to introduce this exciting field to a broader community of (systems) biologists.
- Published
- 2011
39. Universality in solar flare and earthquake occurrence
- Author
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L. de Arcangelis, Cataldo Godano, Eugenio Lippiello, Mario Nicodemi, DE ARCANGELIS, Lucilla, Godano, Cataldo, Lippiello, Eugenio, and Nicodemi, M.
- Subjects
Physics ,Temporal clustering ,WAITING-TIME DISTRIBUTION ,Solar flare ,Statistical Mechanics (cond-mat.stat-mech) ,Stochastic process ,SELF-ORGANIZED CRITICALITY ,General Physics and Astronomy ,FOS: Physical sciences ,Induced seismicity ,Power law ,PARAMETERS ,Universality (dynamical systems) ,law.invention ,Physics::Geophysics ,PHYSICS ,Theoretical physics ,law ,stochastic phenomena ,TURBULENCE ,Statistical physics ,Condensed Matter - Statistical Mechanics ,Flare - Abstract
Earthquakes and solar flares are phenomena involving huge and rapid releases of energy characterized by complex temporal occurrence. By analyzing available experimental catalogs, we show that the stochastic processes underlying these apparently different phenomena have universal properties. Namely, both problems exhibit the same distributions of sizes, interoccurrence times, and the same temporal clustering: We find after flare sequences with power law temporal correlations as the Omori law for seismic sequences. The observed universality suggests a common approach to the interpretation of both phenomena in terms of the same driving physical mechanism.
- Published
- 2006
40. Students’ Reasoning About One-Object Stochastic Phenomena in an ICT-Environment
- Abstract
This paper focuses on the different ways in which students in lower secondary school (14–16 year olds) experience compound random events, presented to them in the form of combined junctions. A carefully designed ICT environment was developed enabling the students to interact with different representations of such structures. Data for the analysis was gathered from two interview sessions. The analysis of the interaction is based on constructivist principles on learning; i.e. we adopted a student-oriented perspective, taking into consideration the different ways students try to make sense of chance encounters. Our results show how some students give priority to geometrical and physical concerns, and we discuss how seeking causal explanations of random phenomena may have encouraged this. With respect to numerically oriented models a division strategy appears to stand out as the preferred one.
- Published
- 2007
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