Long-Term Control of Peary Caribou Numbers by Unpredictable, Exceptionally Severe Snow or Ice Conditions in a Non-equilibrium Grazing System

ARCTIC ◽  
2009 ◽  
Vol 62 (2) ◽  
Author(s):  
Frank L. Miller ◽  
Samuel J. Barry
Keyword(s):  
Grazing System ◽  
Ice Conditions ◽  
Non Equilibrium

scholarly journals Non-Equilibrium Liouville and Wigner Equations: Classical Statistical Mechanics and Chemical Reactions for Long Times

Entropy ◽  
2019 ◽  
Vol 21 (2) ◽  
pp. 179 ◽  
Author(s):  
Ramon Álvarez-Estrada
Keyword(s):  
Orthogonal Polynomials ◽  
Chemical Reactions ◽  
Thermal Equilibrium ◽  
Three Dimensional ◽  
Liapunov Function ◽  
Heat Bath ◽  
Wigner Functions ◽  
Statistical Systems ◽  
Non Equilibrium

We review and improve previous work on non-equilibrium classical and quantum statistical systems, subject to potentials, without ab initio dissipation. We treat classical closed three-dimensional many-particle interacting systems without any “heat bath” ( h b ), evolving through the Liouville equation for the non-equilibrium classical distribution W c , with initial states describing thermal equilibrium at large distances but non-equilibrium at finite distances. We use Boltzmann’s Gaussian classical equilibrium distribution W c , e q , as weight function to generate orthogonal polynomials ( H n ’s) in momenta. The moments of W c , implied by the H n ’s, fulfill a non-equilibrium hierarchy. Under long-term approximations, the lowest moment dominates the evolution towards thermal equilibrium. A non-increasing Liapunov function characterizes the long-term evolution towards equilibrium. Non-equilibrium chemical reactions involving two and three particles in a h b are studied classically and quantum-mechanically (by using Wigner functions W). Difficulties related to the non-positivity of W are bypassed. Equilibrium Wigner functions W e q generate orthogonal polynomials, which yield non-equilibrium moments of W and hierarchies. In regimes typical of chemical reactions (short thermal wavelength and long times), non-equilibrium hierarchies yield approximate Smoluchowski-like equations displaying dissipation and quantum effects. The study of three-particle chemical reactions is new.

scholarly journals Analysis of dynamics for anomalies of the ice cover in the Okhotsk Sea in the period from 1882 to 2015

2016 ◽  
Vol 185 (2) ◽  
pp. 228-239
Author(s):  
Vladimir M. Pishchalnik ◽  
Valery A. Romanyuk ◽  
Igor G. Minervin ◽  
Alevtina S. Batuhtina
Keyword(s):  
Time Series ◽  
Air Temperature ◽  
Regime Shift ◽  
Ice Cover ◽  
Satellite Observations ◽  
Okhotsk Sea ◽  
Ice Conditions ◽  
The Mean ◽  
Analysis Of Dynamics

The time-series for the ice cover dynamics in the Okhotsk Sea in the period from 1882 to 2015 are reconstructed on the base of shipboard, airborne, and satellite observations and measurements of the air temperature at the coastal meteorological stations. Abnormality of the ice conditions is estimated relative to the “climate norm” determined as the mean seasonal variation for the 1961-1990. Long-term variability of the ice cover is analyzed. Its regime shift with change of trend is revealed in the late 1970s - early 1980s that corresponds to the regime shift of the air temperature variability in the northern hemisphere.

The impact of denying sea ice information on the predictability of atmospheric processes over the Arctic and at mid-latitude regions

2020 ◽  
Author(s):  
Leandro Ponsoni ◽  
Daniela Flocco ◽  
François Massonnet ◽  
Steve Delhaye ◽  
Ed Hawkins ◽  
...  
Keyword(s):  
Sea Ice ◽  
General Circulation ◽  
Model Comparison ◽  
General Circulation Models ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Atmospheric Processes ◽  
Ice Conditions ◽  
The Impact

<p>In this work, we make use of an inter-model comparison and of a perfect model approach, in which model outputs are used as true reference states, to assess the impact that denying sea ice information has on the prediction of atmospheric processes, both over the Arctic and at mid-latitude regions. To do so, two long-term control runs (longer than 250 years) were generated with two state-of-the-art General Circulation Models (GCM), namely EC-Earth and HadGEM. From these two reference states, we have identified three different years in which the Arctic sea ice volume (SIV) was (i) maximum, (ii) minimum and (iii) a representative case for the mean state. By departing from each of these three dates (not necessarily the same for the two models), we generated a set of experiments in which the control runs are restarted both from original and climatological sea ice conditions. Here, climatological sea ice conditions are estimated as the time-average of sea ice parameters from the respective long-term control runs. The experiments are 1-year long and all of them start in January when ice is still thin, snow depth is small, air-ocean temperatures contrast the most and, therefore, the heat conductive flux in sea ice (at the surface) is nearly maximum. To robustly separate the response to degrading the initial sea ice state from background internal variability, each of the two counterfactual experiments (reference and climatological) consists of 50 ensembles members. Threstatedese ensembles are generated by adding small random perturbations to the sea surface temperature (EC-Earth) or to the air temperature (HadGEM) fields. Preliminary results reinforce the importance of having the right sea ice state for improving the (sub-)seasonal prediction of atmospheric parameters (e.g., 2m-temperature and geopotential) and circulation (e.g., Westerlies and Jet Stream) not only over the Arctic, but also at mid-latitude regions.</p>

scholarly journals Effects of long-term cattle market conditions on continuous season-long and rotational grazing system revenues

2020 ◽  
Vol 42 (3) ◽  
pp. 227
Author(s):  
J. L. Windh ◽  
J. P. Ritten ◽  
J. D. Derner ◽  
S. Paisley ◽  
B. Lee
Keyword(s):  
Rotational Grazing ◽  
Market Conditions ◽  
Net Returns ◽  
Continuous Grazing ◽  
Grazing System ◽  
Grazing Systems ◽  
Time Of Year ◽  
One Year ◽  
Cattle Market

In this study we evaluated the combination of long-term market conditions and the price slide in the cattle market on revenues associated with continuous and rotational grazing systems. A price slide is a market phenomenon in which lighter cattle sell at a higher price per unit of liveweight compared with their heavier counterparts. We used actual herd average starting and ending weights in this market analysis, and analysed the outcome using five years’ data from a continuous and rotational comparative grazing study. Despite consistently lower weight gains with rotational grazing, differences in gross revenues per steer between grazing treatments ranged from US$43.46 to minus $5.72 across the study years. We observed annual differences in the net returns across years between the two grazing systems; net returns were greater for steers in the continuous grazing treatment in three of the five years, one year with net returns that did not differ between systems, and one year in which net returns were lower with continuous grazing. These variable results showcase the complexity in having both differences in end of grazing season weight classes between the grazing systems and the differential effects of price slide among weight classes. Therefore, we argue that it may be a better management strategy for land managers to determine the optimal ending weights and the time of year to market livestock to meet the goals of an operation, rather than trying to determine which grazing system is ‘best’.

scholarly journals Variability of ice conditions of the Bering sea and assessment of the possibility of their modelling

2019 ◽  
Vol 59 (6) ◽  
pp. 920-927
Author(s):  
V. V. Plotnikov ◽  
N. M. Vakulskaya ◽  
V. A. Dubina
Keyword(s):  
Sea Ice ◽  
Interannual Variability ◽  
Bering Sea ◽  
Ice Cover ◽  
Practical Application ◽  
Seasonal And Interannual Variability ◽  
Proposed Model ◽  
Ice Conditions ◽  
The Bering Sea

Various aspects of seasonal and interannual variability of the sea ice cover are estimated on the basis of all available the Bering Sea ice data from 1960 to 2017. The possibility of long-term and superlong-term modeling of the ice cover is investigated. Results of tests are given, and a conclusion about prospects of the proposed model and an opportunity of its practical application is done.

scholarly journals The impact of antigenic escape on the evolution of virulence

2021 ◽  
Author(s):  
Akira Sasaki ◽  
Sébastien Lion ◽  
Mike Boots
Keyword(s):  
Complex Disease ◽  
Immune Escape ◽  
Transmission Rate ◽  
Antigenic Drift ◽  
Long Term Outcome ◽  
Equilibrium Dynamics ◽  
Evolution Of Virulence ◽  
The Impact ◽  
Non Equilibrium

AbstractUnderstanding the evolutionary drivers determining the transmission rate and virulence of pathogens remains an important challenge for evolutionary theory with clear implications to the control of human, agricultural and wildlife infectious disease. Although disease is often very dynamic, classical theory examines the long-term outcome of evolution at equilibrium and, in simple models, typically predicts that R0 is maximized. For example, immune escape may lead to complex disease dynamics including repeated epidemics, fluctuating selection and diversification. Here we model the impact of antigenic drift and escape on the evolution of virulence and show analytically that these non-equilibrium dynamics select for more acute pathogens with higher virulence. Specifically, under antigenic drift and when partial cross immunity leads to antigenic escape, our analysis predicts the long-term maximization of the intrinsic growth rate of the parasite resulting in more acute and virulent pathogens than those predicted by classic R0 maximization. Furthermore, it follows that these pathogens will have a lower R0 leading to implications for epidemic, endemic behavior and control. Our analysis predicts both the timings and outcomes of antigenic shifts leading to repeated epidemics and predicts the increase in variation in both antigenicity and virulence before antigenic escape. There is considerable variation in the degree of antigenic escape that occurs across pathogens and our results may help to explain the difference in virulence between related pathogens most clearly seen in the human A, B and C influenzas. More generally our results show the importance of examining the evolutionary consequences of non-equilibrium dynamics.

Application of microwave remote sensing to studies of sea ice

1983 ◽  
Vol 309 (1508) ◽  
pp. 433-445 ◽  
Keyword(s):  
Remote Sensing ◽  
Sea Ice ◽  
Microwave Remote Sensing ◽  
Polar Regions ◽  
Short Term ◽  
Ice Conditions ◽  
Remote Sensing Techniques ◽  
Microwave Techniques ◽  
Term Monitoring

Monitoring of snow and ice is of importance for meteorological and climate research and applications, for hydrological purposes and for navigation and offshore activity in polar regions. For some of these applications long-term monitoring on a mesoscale and a synoptic scale is sufficient, whereas other applications require short-term observation on a mesoscale. This applies especially to forecasting of sea ice conditions, for instance. In the latter cases microwave remote sensing is the only technique that may deliver reliable and timely data irrespective of light, weather and cloud conditions. In the polar regions, this feature is of utmost importance. All known microwave remote-sensing techniques have demonstrated their applicability in polar regions, in particular in connection with observations of sea ice. It has also been shown that a combination of simultaneously acquired data from different sensors may be of advantage in parameter retrieval. This paper reviews the monitoring requirements and the microwave techniques available for this purpose with a view to snow and sea ice research and applications.

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