scholarly journals Ocean modelling for climate studies: Eliminating short time scales in long-term, high-resolution studies of ocean circulation

2006 ◽  
Vol 44 (9-10) ◽  
pp. 870-886 ◽  
Author(s):  
Balasubramanya T. Nadiga ◽  
Mark Taylor ◽  
Jens Lorenz
Keyword(s):  
High Resolution ◽  
Time Scales ◽  
Ocean Circulation ◽  
Ocean Modelling ◽  
Short Time ◽  
Climate Studies

The Spread of Pollutants from Harbour Sludge Depots

1984 ◽  
Vol 16 (3-4) ◽  
pp. 623-633
Author(s):  
M Loxham ◽  
F Weststrate
Keyword(s):  
Time Scales ◽  
Molecular Diffusion ◽  
Near Field ◽  
Parameter Analysis ◽  
Migration Patterns ◽  
Long Time ◽  
Dilution Effects ◽  
Short Time ◽  
Harbour Sludge

It is generally agreed that both the landfill option, or the civil techniques option for the final disposal of contaminated harbour sludge involves the isolation of the sludge from the environment. For short time scales, engineered barriers such as a bentonite screen, plastic sheets, pumping strategies etc. can be used. However for long time scales the effectiveness of such measures cannot be counted upon. It is thus necessary to be able to predict the long term environmenttal spread of contaminants from a mature landfill. A model is presented that considers diffusion and adsorption in the landfill site and convection and adsorption in the underlaying aquifer. From a parameter analysis starting form practical values it is shown that the adsorption behaviour and the molecular diffusion coefficient of the sludge, are the key parameters involved in the near field. The dilution effects of the far field migration patterns are also illustrated.

scholarly journals Stability analysis of three exoplanet systems

2020 ◽  
Vol 494 (2) ◽  
pp. 2280-2288
Author(s):  
J P Marshall ◽  
J Horner ◽  
R A Wittenmyer ◽  
J T Clark ◽  
M W Mengel
Keyword(s):  
Time Scales ◽  
Planetary Systems ◽  
Orbital Parameters ◽  
Exoplanetary Systems ◽  
Best Fitting ◽  
The Stability ◽  
Short Time ◽  
Exoplanet Systems ◽  
Best Fit

ABSTRACT The orbital solutions of published multiplanet systems are not necessarily dynamically stable on time-scales comparable to the lifetime of the system as a whole. For this reason, dynamical tests of the architectures of proposed exoplanetary systems are a critical tool to probe the stability and feasibility of the candidate planetary systems, with the potential to point the way towards refined orbital parameters of those planets. Such studies can even help in the identification of additional companions in such systems. Here, we examine the dynamical stability of three planetary systems, orbiting HD 67087, HD 110014, and HD 133131A. We use the published radial velocity measurements of the target stars to determine the best-fitting orbital solutions for these planetary systems using the systemic console. We then employ the N-body integrator mercury to test the stability of a range of orbital solutions lying within 3σ of the nominal best fit for a duration of 100 Myr. From the results of the N-body integrations, we infer the best-fitting orbital parameters using the Bayesian package astroemperor. We find that both HD 110014 and HD 133131A have long-term stable architectures that lie within the 1σ uncertainties of the nominal best fit to their previously determined orbital solutions. However, the HD 67087 system exhibits a strong tendency towards instability on short time-scales. We compare these results to the predictions made from consideration of the angular momentum deficit criterion, and find that its predictions are consistent with our findings.

scholarly journals Development of a longterm dataset of solid/liquid precipitation

2011 ◽  
Vol 6 (1) ◽  
pp. 39-43 ◽  
Author(s):  
B. Chimani ◽  
R. Böhm ◽  
C. Matulla ◽  
M. Ganekind
Keyword(s):  
High Resolution ◽  
20Th Century ◽  
Alpine Region ◽  
Nonlinear Relationship ◽  
Solid Precipitation ◽  
Temperature And Precipitation ◽  
Solid Liquid ◽  
Climate Studies ◽  
Liquid Precipitation

Abstract. Solid precipitation (mainly snow, but snow and ice pellets or hail as well), is an important parameter for climate studies. But as this parameter usually is not available operationally before the second part of the 20th century and nowadays is not reported by automatic stations, information usable for long term climate studies is rare. Therefore a proxy for the fraction of solid precipitation based on a nonlinear relationship between the percentage of solid precipitation and monthly mean temperature was developed for the Greater Alpine Region of Europe and applied to the existing longterm high resolution temperature and precipitation grids (5 arcmin). In this paper the method is introduced and some examples of the resulting datasets available at monthly resolution for 1800–2003 are given.

scholarly journals Brief Communication: Evidence of a developing Polynya off Commonwealth Bay, East Antarctica, triggered by grounding of iceberg

2016 ◽  
Author(s):  
Christopher J. Fogwill ◽  
Erik van Sebille ◽  
Eva A. Cougnon ◽  
Chris S. M. Turney ◽  
Steve R. Rintoul ◽  
...  
Keyword(s):  
High Resolution ◽  
Ocean Circulation ◽  
Large Scale ◽  
Bottom Water ◽  
High Salinity ◽  
Shelf Water ◽  
Antarctic Bottom Water ◽  
Ocean Modelling ◽  
Glacier Tongue ◽  
The Impact

Abstract. The dramatic calving of the Mertz Glacier Tongue in 2010, triggered by the impact of iceberg B09B, reshaped the oceanographic regime across the Mertz Polynya and Commonwealth Bay, regions where high salinity shelf water (HSSW) is formed, the precursor to Antarctic bottom water (AABW). Here we compare post-calving observations with high-resolution ocean modelling which suggest that this reconfiguration has led to the development of a new polynya off Commonwealth Bay, where HSSW production continues by the grounding of B09B. Our findings demonstrate how local changes in icescape can impact formation of AABW, with implications for large-scale ocean circulation and climate.

scholarly journals A survey for variable young stars with small telescopes: II – mapping a protoplanetary disc with stable structures at 0.15 au

2020 ◽  
Vol 493 (1) ◽  
pp. 184-198 ◽  
Author(s):  
Jack J Evitts ◽  
Dirk Froebrich ◽  
Aleks Scholz ◽  
Jochen Eislöffel ◽  
Justyn Campbell-White ◽  
...  
Keyword(s):  
Time Scales ◽  
Broad Band ◽  
T Tauri ◽  
Low Levels ◽  
Short Time ◽  
Citizen Science Project ◽  
The Hill ◽  
Colour Terms ◽  
High Cadence

ABSTRACT The HOYS citizen science project conducts long-term, multifilter, high-cadence monitoring of large YSO samples with a wide variety of professional and amateur telescopes. We present the analysis of the light curve of V1490 Cyg in the Pelican Nebula. We show that colour terms in the diverse photometric data can be calibrated out to achieve a median photometric accuracy of 0.02 mag in broad-band filters, allowing detailed investigations into a variety of variability amplitudes over time-scales from hours to several years. Using Gaia DR2, we estimate the distance to the Pelican Nebula to be 870 $^{+70}_{-55}$ pc. V1490 Cyg is a quasi-periodic dipper with a period of 31.447 ± 0.011 d. The obscuring dust has homogeneous properties, and grains larger than those typical in the ISM. Larger variability on short time-scales is observed in U and Rc−H α, with U amplitudes reaching 3 mag on time-scales of hours, indicating that the source is accreting. The H α equivalent width and NIR/MIR colours place V1490 Cyg between CTTS/WTTS and transition disc objects. The material responsible for the dipping is located in a warped inner disc, about 0.15 au from the star. This mass reservoir can be filled and emptied on time-scales shorter than the period at a rate of up to 10−10 M⊙ yr−1, consistent with low levels of accretion in other T Tauri stars. Most likely, the warp at this separation from the star is induced by a protoplanet in the inner accretion disc. However, we cannot fully rule out the possibility of an AA Tau-like warp, or occultations by the Hill sphere around a forming planet.

scholarly journals Short term changes in methanol emission and pectin methylesterase activity are not directly affected by light in <i>Lycopersicon esculentum</i>

2011 ◽  
Vol 8 (4) ◽  
pp. 1023-1030 ◽  
Author(s):  
P. Y. Oikawa ◽  
L. Li ◽  
M. P. Timko ◽  
J. E. Mak ◽  
M. T. Lerdau
Keyword(s):  
Time Scales ◽  
Pectin Methylesterase ◽  
Light Activation ◽  
Short Term ◽  
Substrate Limitation ◽  
Emission Models ◽  
Seasonal Time Scale ◽  
Short Time ◽  
Cell Wall Expansion

Abstract. Plants are an important source of atmospheric methanol (MeOH), the second most abundant organic gas after methane. Factors regulating phytogenic MeOH production are not well constrained in current MeOH emission models. Previous studies have indicated that light may have a direct influence on MeOH production. As light is known to regulate cell wall expansion, it was predicted that light would stimulate MeOH production through the pectin methylesterase (PME) pathway. MeOH emissions normalized for stomatal conductance (gs) did not, however, increase with light over short time scales (20–30 min). After experimentally controlling for gs and temperature, no light activation of PME activity or MeOH emission was observed. The results clearly demonstrate that light does not directly influence short-term changes in MeOH production and emission. Our data suggest that substrate limitation may be important in regulating MeOH production over short time scales. Future investigation of the long-term impacts of light on MeOH production may increase understanding of MeOH emission dynamics at the seasonal time scale.

scholarly journals Optical variability of quasars: a damped random walk

2013 ◽  
Vol 9 (S304) ◽  
pp. 395-398 ◽  
Author(s):  
Željko Ivezić ◽  
Chelsea MacLeod
Keyword(s):  
Random Walk ◽  
Time Scales ◽  
Model Parameters ◽  
Optical Wavelength ◽  
Long Time ◽  
Asymptotic Variability ◽  
Short Time ◽  
Quasar Variability ◽  
Best Fit

AbstractA damped random walk is a stochastic process, defined by an exponential covariance matrix that behaves as a random walk for short time scales and asymptotically achieves a finite variability amplitude at long time scales. Over the last few years, it has been demonstrated, mostly but not exclusively using SDSS data, that a damped random walk model provides a satisfactory statistical description of observed quasar variability in the optical wavelength range, for rest-frame timescales from 5 days to 2000 days. The best-fit characteristic timescale and asymptotic variability amplitude scale with the luminosity, black hole mass, and rest wavelength, and appear independent of redshift. In addition to providing insights into the physics of quasar variability, the best-fit model parameters can be used to efficiently separate quasars from stars in imaging surveys with adequate long-term multi-epoch data, such as expected from LSST.

What sets the long-term level of sympathetic nerve activity: is there a role for arterial baroreceptors?

2004 ◽  
Vol 286 (1) ◽  
pp. R1-R12 ◽  
Author(s):  
Simon C. Malpas
Keyword(s):  
Blood Pressure ◽  
Time Scales ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
New Technologies ◽  
Nerve Activity ◽  
Arterial Baroreceptors ◽  
Experimental Approaches ◽  
Short Time

Much of our knowledge of the influence of the sympathetic nervous system on the control of blood pressure is built on experimental approaches that focus very much on time scales <24 h. Although direct recordings of sympathetic nerve activity (SNA) over short time scales provide important information, it is difficult to place their relevance over the longer term where the development of chronic changes in blood pressure are likely to be a mixture of hormonal, renal, and neural influences. Recently new experimental approaches are now revealing a possible role for arterial baroreceptors in the chronic regulation of SNA. These studies reveal that chronic increases in blood pressure are associated with chronic changes in SNA that may be due to nonresetting of the blood pressure-SNA baroreflex relationship. This review discusses the implications of such information, highlighting new technologies for long-term recording of SNA that appear to hold much promise for revealing the role of SNA to the kidney for the long-term control of blood pressure.

scholarly journals Linking long- and short-term emission variability in pulsars

2019 ◽  
Vol 488 (4) ◽  
pp. 5702-5712 ◽  
Author(s):  
P R Brook ◽  
A Karastergiou ◽  
S Johnston
Keyword(s):  
Time Scales ◽  
Radio Pulsars ◽  
Physical Processes ◽  
Short Term ◽  
Monitoring Technique ◽  
Wide Range ◽  
Statistical Detection ◽  
Short Time

ABSTRACT It is now known that the emission from radio pulsars can vary over a wide range of time-scales, from fractions of seconds to decades. However, it is not yet known if long- and short-term emission variability are caused by the same physical processes. It has been observed that long-term emission variability is often correlated with rotational changes in the pulsar. We do not yet know if the same is true of short-term emission variability, as the rotational changes involved cannot be directly measured over such short time-scales. To remedy this, we propose a continuous pulsar monitoring technique that permits the statistical detection of any rotational changes in nulling and mode-changing pulsars with certain properties. Using a simulation, we explore the range of pulsar properties over which such an experiment would be possible.

scholarly journals Long-term evolution of CFS-unstable neutron stars and the role of differential rotation on short time-scales

2018 ◽  
Vol 482 (3) ◽  
pp. 3045-3057 ◽  
Author(s):  
A I Chugunov
Keyword(s):  
Neutron Star ◽  
Time Scales ◽  
Differential Rotation ◽  
Time Scale ◽  
Evolution Equations ◽  
Long Term Evolution ◽  
Cooling Power ◽  
Term Evolution ◽  
Short Time

Abstract I consider differential rotation, associated with radiation-driven Chandrasekhar–Friedman–Schutz (CFS) instability, and respective observational manifestations. I focus on the evolution of the apparent spin frequency, which is typically associated with the motion of a specific point on the stellar surface (e.g. polar cap). I start from long-term evolution (on the time-scale when instability significantly changes the spin frequency). For this case, I reduce the evolution equations to one differential equation and I demonstrate that it can be directly derived from energy conservation law. This equation governs the evolution rate through a sequence of thermally equilibrium states and it provides linear coupling for the cooling power and rotation energy losses via gravitational wave emission. In particular, it shows that differential rotation does not affect long-term spin-down. In contrast, on short time-scales, differential rotation can significantly modify the apparent spin-down, if we examine a strongly unstable star with a very small initial amplitude for the unstable mode. This statement is confirmed by considering a Newtonian non-magnetized perfect fluid and dissipative stellar models as well as a magnetized stellar model. For example, despite the fact that the widely applied evolution equations predict effective spin to be constant in the absence of dissipation, the CFS-unstable star should be observed as spinning-down. However, the effects of differential rotation on apparent spin-down are negligible for realistic models of neutron star recycling, unless the neutron star is non-magnetized, the r-mode amplitude is modulated faster than the shear viscosity dissipation time-scale, and the amplitude is large enough that spin-down can be measured on a modulation time-scale.

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