Articles de revues : « Idealised configuration »

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Maher, Penelope, et Paul Earnshaw. « The Flexible Modelling Framework for the Met Office Unified Model (Flex-UM, using UM 12.0 release) ». Geoscientific Model Development 15, n^o 3 (9 février 2022) : 1177–94. http://dx.doi.org/10.5194/gmd-15-1177-2022.

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Abstract. The Met Office Unified Model (UM) is a world-leading atmospheric weather and climate model. In addition to comprehensive simulations of the atmosphere, the UM is capable of running idealised simulations, such as the dry physics Held–Suarez test case, radiative convective equilibrium and simulating planetary atmospheres other than Earth. However, there is a disconnect between the simplicity of the idealised UM model configurations and the full complexity of the UM. This gap inhibits the broad use of climate model hierarchy approaches within the UM. To fill this gap, we have developed the Flexible Modelling Framework for the UM – Flex-UM – which broadens the climate model hierarchy capabilities within the UM. Flex-UM was designed to replicate the atmospheric physics of the Geophysical Fluid Dynamics Laboratory (GFDL) idealised moist physics aqua-planet model. New parameterisations have been implemented in Flex-UM, including simplified schemes for convection, large-scale precipitation, radiation, boundary layer and sea surface temperature (SST) boundary conditions. These idealised parameterisations have been implemented in a modular way, so that each scheme is available for use in any model configuration. This has the advantage that we can incrementally add or remove complexity within the model hierarchy. We compare Flex-UM to ERA5 and aqua-planet simulations using the Isca climate modelling framework (based on the GFDL moist physics aqua-planet model) and comprehensive simulations of the UM (using the GA7.0 configuration). We also use two SST boundary conditions to compare the models (fixed SST and a slab ocean). We find the Flex-UM climatologies are similar to both Isca and GA7.0 (though Flex-UM is generally a little cooler, with higher relative humidity and a less pronounced storm track). Flex-UM has a single Intertropical Convergence Zone (ITCZ) in the slab-ocean simulation but a double-ITCZ in the fixed-SST simulation. Further work is needed to ensure that the atmospheric energy budget closes to within 1–2 W m−2, as the current configuration of Flex-UM gains 9–11 W m−2 (the range covers the two SST boundary conditions). Flex-UM greatly extends the modelling hierarchy capabilities of the UM and offers a simplified framework for developing, testing and evaluating parameterisations within the UM.

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Schröter, Jennifer, Daniel Rieger, Christian Stassen, Heike Vogel, Michael Weimer, Sven Werchner, Jochen Förstner et al. « ICON-ART 2.1 : a flexible tracer framework and its application for composition studies in numerical weather forecasting and climate simulations ». Geoscientific Model Development 11, n^o 10 (5 octobre 2018) : 4043–68. http://dx.doi.org/10.5194/gmd-11-4043-2018.

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Abstract. Atmospheric composition studies on weather and climate timescales require flexible, scalable models. The ICOsahedral Nonhydrostatic model with Aerosols and Reactive Trace gases (ICON-ART) provides such an environment. Here, we introduce the most up-to-date version of the flexible tracer framework for ICON-ART and explain its application in one numerical weather forecast and one climate related case study. We demonstrate the implementation of idealised tracers and chemistry tendencies of different complexity using the ART infrastructure. Using different ICON physics configurations for weather and climate with ART, we perform integrations on different timescales, illustrating the model's performance. First, we present a hindcast experiment for the 2002 ozone hole split with two different ozone chemistry schemes using the numerical weather prediction physics configuration. We compare the hindcast with observations and discuss the confinement of the vortex split using an idealised tracer diagnostic. Secondly, we study AMIP-type integrations using a simplified chemistry scheme in conjunction with the climate physics configuration. We use two different simulations: the interactive simulation, where modelled ozone is coupled back to the radiation scheme, and the non-interactive simulation that uses a default background climatology of ozone. Additionally, we introduce changes of water vapour by methane oxidation for the interactive simulation. We discuss the impact of stratospheric ozone and water vapour variations in the interactive and non-interactive integrations on the water vapour tape recorder, as a measure of tropical upwelling changes. Additionally we explain the seasonal evolution and latitudinal distribution of the age of air. The age of air is a measure of the strength of the meridional overturning circulation with young air in the tropical upwelling region and older air in polar winter downwelling regions. We conclude that our flexible tracer framework allows for tailor-made configurations of ICON-ART in weather and climate applications that are easy to configure and run well.

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Manchester, Emily Louise, Dylan Roi, Boram Gu, Xiao Yun Xu et Kyriakos Lobotesis. « Modelling Combined Intravenous Thrombolysis and Mechanical Thrombectomy in Acute Ischaemic Stroke : Understanding the Relationship between Stent Retriever Configuration and Clot Lysis Mechanisms ». Life 11, n^o 11 (20 novembre 2021) : 1271. http://dx.doi.org/10.3390/life11111271.

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Background: Combined intravenous thrombolysis and mechanical thrombectomy (IVT-MT) is a common treatment in acute ischaemic stroke, however the interaction between IVT and MT from a physiological standpoint is poorly understood. In this pilot study, we conduct numerical simulations of combined IVT-MT with various idealised stent retriever configurations to evaluate performance in terms of complete recanalisation times and lysis patterns. Methods: A 3D patient-specific geometry of a terminal internal carotid artery with anterior and middle cerebral arteries is reconstructed, and a thrombus is artificially implanted in the MCA branch. Various idealised stent retriever configurations are implemented by varying stent diameter and stent placement, and a configuration without a stent retriever provides a baseline for comparison. A previously validated multi-level model of thrombolysis is used, which incorporates blood flow, drug transport, and fibrinolytic reactions within a fibrin thrombus. Results: Fastest total recanalisation was achieved in the thrombus without a stent retriever, with lysis times increasing with stent retriever diameter. Two mechanisms of clot lysis were established: axial and radial permeation. Axial permeation from the clot front was the primary mechanism of lysis in all configurations, as it facilitated increased protein binding with fibrin fibres. Introducing a stent retriever channel allowed for radial permeation, which occurred at the fluid-thrombus interface, although lysis was much slower in the radial direction because of weaker secondary velocities. Conclusions: Numerical models can be used to better understand the complex physiological relationship between IVT and MT. Two different mechanisms of lysis were established, providing a basis towards improving the efficacy of combined treatments.

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Eberhard, Julius, Oliver E. Bevan, Georg Feulner, Stefan Petri, Jeroen van Hunen et James U. L. Baldini. « Sensitivity of Neoproterozoic snowball-Earth inceptions to continental configuration, orbital geometry, and volcanism ». Climate of the Past 19, n^o 11 (6 novembre 2023) : 2203–35. http://dx.doi.org/10.5194/cp-19-2203-2023.

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Abstract. The Cryogenian period (720–635 million years ago) in the Neoproterozoic era featured two phases of global or near-global ice cover termed “snowball Earth”. Climate models of all kinds indicate that the inception of these phases must have occurred in the course of a self-amplifying ice–albedo feedback that forced the climate from a partially ice-covered to a snowball state within a few years or decades. The maximum concentration of atmospheric carbon dioxide (CO2) allowing such a drastic shift depends on the choice of model, the boundary conditions prescribed in the model, and the amount of climatic variability. Many previous studies reported values or ranges for this CO2 threshold but typically tested only a very few different boundary conditions or excluded variability due to volcanism. Here we present a comprehensive sensitivity study determining the CO2 thresholds in different scenarios for the Cryogenian continental configuration, orbital geometry, and short-term volcanic cooling effects in a consistent model framework using the climate model of intermediate complexity CLIMBER-3α. The continental configurations comprise two palaeogeographic reconstructions for each of both snowball-Earth onsets as well as two idealised configurations with either uniformly dispersed continents or a single polar supercontinent. Orbital geometries are sampled as multiple different combinations of the parameters obliquity, eccentricity, and argument of perihelion. For volcanic eruptions, we differentiate between single globally homogeneous perturbations, single zonally resolved perturbations, and random sequences of globally homogeneous perturbations with realistic statistics. The CO2 threshold lies between 10 and 250 ppm for all simulations. While the thresholds for the idealised continental configurations differ by a factor of up to 19, the CO2 thresholds for the continental reconstructions differ by only 6 %–44 % relative to the lower thresholds. Changes in orbital geometry account for variations in the CO2 threshold of up to 30 % relative to the lowest threshold. The effects of volcanic perturbations largely depend on the orbital geometry and the corresponding structure of coexisting stable states. A very large peak reduction in net solar radiation of 20 or 30 W m−2 can shift the CO2 threshold by the same order of magnitude as or less than the orbital geometry. Exceptionally large eruptions of up to −40 W m−2 shift the threshold by up to 40 % for one orbital configuration. Eruptions near the Equator tend to, but do not always, cause larger shifts than eruptions at high latitudes. The effects of realistic eruption sequences are mostly determined by their largest events. In the presence of particularly intense small-magnitude volcanism, this effect can go beyond the ranges expected from single eruptions.

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Basley, Jérémy, Laurent Perret et Romain Mathis. « Structure of high Reynolds number boundary layers over cube canopies ». Journal of Fluid Mechanics 870 (10 mai 2019) : 460–91. http://dx.doi.org/10.1017/jfm.2019.274.

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The influence of a cube-based canopy on coherent structures of the flow was investigated in a high Reynolds number boundary layer (thickness $\unicode[STIX]{x1D6FF}\sim 30\,000$ wall units). Wind tunnel experiments were conducted considering wall configurations that represent three idealised urban terrains. Stereoscopic particle image velocimetry was employed using a large field of view in a streamwise–spanwise plane ($0.55\unicode[STIX]{x1D6FF}\times 0.5\unicode[STIX]{x1D6FF}$) combined to two-point hot-wire measurements. The analysis of the flow within the inertial layer highlights the independence of its characteristics from the wall configuration. The population of coherent structures is in agreement with that of smooth-wall boundary layers, i.e. consisting of large- and very-large-scale motions, sweeps and ejections, as well as smaller-scale vortical structures. The characteristics of vortices appear to be independent of the roughness configuration while their spatial distribution is closely linked to large meandering motions of the boundary layer. The canopy geometry only significantly impacts the wall-normal exchanges within the roughness sublayer. Bi-dimensional spectral analysis demonstrates that wall-normal velocity fluctuations are constrained by the presence of the canopy for the densest investigated configurations. This threshold in plan area density above which large scales from the overlying boundary layer can penetrate the roughness sublayer is consistent with the change of the flow regime reported in the literature and constitutes a major difference with flows over vegetation canopies.

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Siemes, Rutger, Trang Minh Duong, Pim Willemsen, Bas Borsje et Suzanne Hulscher. « ESTUARINE-WIDE SEDIMENT DYNAMICS UNDER HUMAN INTERVENTIONS AND CLIMATE CHANGE EFFECTS ; AN IDEALISED MODEL STUDY ». Coastal Engineering Proceedings, n^o 37 (1 septembre 2023) : 12. http://dx.doi.org/10.9753/icce.v37.sediment.12.

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Estuaries worldwide are under constant anthropogenic pressure. They are susceptible to climate change effects, from the sea (sea level rise, changing wave climate) and from the river-side (changing river discharge). Besides, estuaries are channelised and embanked to improve flood safety and to reclaim land, and channels are deepened to allow bigger ships to enter the ports. To optimise estuarine functions and sustainably prepare for future challenges, improved understanding of estuarine sediment dynamics after potential changes in the systems configuration and forcings is desired. This paper aims to assess the annual sediment dynamics of an estuary under a climate change effects, and how this is affected by human interventions.

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GRISOUARD, N., C. STAQUET et T. GERKEMA. « Generation of internal solitary waves in a pycnocline by an internal wave beam : a numerical study ». Journal of Fluid Mechanics 676 (1 avril 2011) : 491–513. http://dx.doi.org/10.1017/jfm.2011.61.

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Oceanic observations from western Europe and the south-western Indian ocean have provided evidence of the generation of internal solitary waves due to an internal tidal beam impinging on the pycnocline from below – a process referred to as ‘local generation’ (as opposed to the more direct generation over topography). Here we present the first direct numerical simulations of such a generation process with a fully nonlinear non-hydrostatic model for an idealised configuration. We show that, depending on the parameters, different modes can be excited and we provide examples of internal solitary waves as first, second and third modes, trapped in the pycnocline. A criterion for the selection of a particular mode is put forward, in terms of phase speeds. In addition, another simpler geometrical criterion is presented to explain the selection of modes in a more intuitive way. Finally, results are discussed and compared with the configuration of the Bay of Biscay.

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ASPDEN, A. J., M. S. DAY et J. B. BELL. « Turbulence–flame interactions in lean premixed hydrogen : transition to the distributed burning regime ». Journal of Fluid Mechanics 680 (31 mai 2011) : 287–320. http://dx.doi.org/10.1017/jfm.2011.164.

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The response of lean (ϕ ≤ 0.4) premixed hydrogen flames to maintained homogeneous isotropic turbulence is investigated using detailed numerical simulation in an idealised three-dimensional configuration over a range of Karlovitz numbers from 10 to 1562. In particular, a focus is placed on turbulence sufficiently intense that the flames can no longer be considered to be in the thin reaction burning regime. This transition to the so-called distributed burning regime is characterised through a number of diagnostics, and the relative roles of molecular and turbulent mixing processes are examined. The phenomenology and statistics of these flames are contrasted with a distributed thermonuclear flame from a related astrophysical study.

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Jemitola, P. O., J. Fielding et P. Stocking. « Joint fixity effect on structural design of a box wing aircraft ». Aeronautical Journal 116, n^o 1178 (avril 2012) : 363–72. http://dx.doi.org/10.1017/s0001924000005261.

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Abstract A computational study was performed to compare the stress distributions in finite element torsion box models of a box wing structure that result from employing four different wing/end fin joint fixities. All considered wings were trimmed in pitch. The joint fixities refer to the type of attachment that connects the tip of the fore and aft wings to the end fin. Using loads from a vortex lattice tool, the analysis determined the best wing-joint fixity of a statically loaded idealised box wing configuration by comparing the stress distributions resulting from the different wing joints in addition to other essential aerodynamic requirements. Analysis of the wing joint fixity indicates that the rigid joint is the most suitable.

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Martin, G. M., et R. C. Levine. « The influence of dynamic vegetation on the present-day simulation and future projections of the South Asian summer monsoon in the HadGEM2 family ». Earth System Dynamics 3, n^o 2 (28 novembre 2012) : 245–61. http://dx.doi.org/10.5194/esd-3-245-2012.

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Abstract. Various studies have shown the importance of Earth System feedbacks in the climate system and the necessity of including these in models used for making climate change projections. The HadGEM2 family of Met Office Unified Model configurations combines model components which facilitate the representation of many different processes within the climate system, including atmosphere, ocean and sea ice, and Earth System components including the terrestrial and oceanic carbon cycle and tropospheric chemistry. We examine the climatology of the Asian summer monsoon in present-day simulations and in idealised climate change experiments. Members of the HadGEM2 family are used, with a common physical framework (one of which includes tropospheric chemistry and an interactive terrestrial and oceanic carbon cycle), to investigate whether such components affect the way in which the monsoon changes. We focus particularly on the role of interactive vegetation in the simulations from these model configurations. Using an atmosphere-only HadGEM2 configuration, we investigate how the changes in land cover which result from the interaction between the dynamic vegetation and the model systematic rainfall biases affect the Asian summer monsoon, both in the present-day and in future climate projections. We demonstrate that the response of the dynamic vegetation to biases in regional climate, such as lack of rainfall over tropical dust-producing regions, can affect both the present-day simulation and the response to climate change forcing scenarios.

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Zheng, Yixi, David P. Stevens, Karen J. Heywood, Benjamin G. M. Webber et Bastien Y. Queste. « Reversal of ocean gyres near ice shelves in the Amundsen Sea caused by the interaction of sea ice and wind ». Cryosphere 16, n^o 7 (28 juillet 2022) : 3005–19. http://dx.doi.org/10.5194/tc-16-3005-2022.

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Abstract. Floating ice shelves buttress the Antarctic Ice Sheet, which is losing mass rapidly mainly due to ocean-driven melting and the associated disruption to glacial dynamics. The local ocean circulation near ice shelves is therefore important for the prediction of future ice mass loss and related sea-level rise as it determines the water mass exchange, heat transport under the ice shelf and resultant melting. However, the dynamics controlling the near-coastal circulation are not fully understood. A cyclonic (i.e. clockwise) gyre circulation (27 km radius) in front of the Pine Island Ice Shelf has previously been identified in both numerical models and velocity observations. Mooring data further revealed a potential reversal of this gyre during an abnormally cold period. Here we present ship-based observations from 2019 to the west of Thwaites Ice Shelf, revealing another gyre (13 km radius) for the first time in this habitually ice-covered region, rotating in the opposite (anticyclonic, anticlockwise) direction to the gyre near Pine Island Ice Shelf, despite similar wind forcing. We use an idealised configuration of MITgcm, with idealised forcing based on ERA5 climatological wind fields and a range of idealised sea ice conditions typical for the region, to reproduce key features of the observed gyres near Pine Island Ice Shelf and Thwaites Ice Shelf. The model driven solely by wind forcing in the presence of ice can reproduce the horizontal structure and direction of both gyres. We show that the modelled gyre direction depends upon the spatial difference in the ocean surface stress, which can be affected by the applied wind stress curl filed, the percentage of wind stress transferred through the ice, and the angle between the wind direction and the sea ice edge. The presence of ice, either it is fast ice/ice shelves blocking the effect of wind or mobile sea ice enhancing the effect of wind, has the potential to reverse the gyre direction relative to ice-free conditions.

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Gabriel, Sherlyn, Jack Denny, Steeve Chung Kim Yuen, Genevieve S. Langdon et Reuben A. Govender. « The Effect of Scaling Building Configuration Blast Experiments on Positive Phase Blast Wave Parameters ». Applied Sciences 13, n^o 10 (12 mai 2023) : 5956. http://dx.doi.org/10.3390/app13105956.

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Explosions in an urban setting can have a significant negative impact. There is a need to further understand the loading effects caused by the blast’s interaction with structures. In conjunction with this, the effects of scaling and understanding the limitations of laboratory experiments are equally important given the cost incurred for full-scale experiments. The aim of this study was to determine the scaling effects on blast wave parameters found for reduced-scale urban blast scenario laboratory experiments. This paper presents the results of numerical modelling and physical experiments on detonating cuboidal PE-4 charges and measuring the pressure in direct line of sight and at three distinct positions around the corner of a small-scale “building” parallel to the rear wall. Two scales were used, namely 75% and 100%. Inter-scaling between 75% and 100% worked fairly well for positions shielded by the corner of the wall. Additionally, the lab-scale results were compared to similar (but not identical) field trials at an equivalent scale of 250%. The comparison between lab-scale idealised testing and the larger-scale field trials published by Gajewksi and Sielicki in 2020, indicated sensitivity to factors such as detonator positioning, explosive material, charge confinement/mounting, building surface roughness, and environment.

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Martin, G. M., et R. C. Levine. « The influence of dynamic vegetation on the present-day simulation and future projections of the South Asian summer monsoon in the HadGEM2 family ». Earth System Dynamics Discussions 3, n^o 2 (3 août 2012) : 759–99. http://dx.doi.org/10.5194/esdd-3-759-2012.

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Abstract. Various studies have shown the importance of Earth System feedbacks in the climate system and the necessity of including these in models used for making climate change projections. The HadGEM2 family of Met Office Unified Model configurations combines model components which facilitate the representation of many different processes within the climate system, including atmosphere, ocean and sea ice, and Earth System components including the terrestrial and oceanic carbon cycle and tropospheric chemistry. We examine the climatology of the Asian summer monsoon in present-day simulations and in idealised climate change experiments in which a quadrupling of CO2 is applied as a step change. Members of the HadGEM2 family are used, with a common physical framework, one of which includes tropospheric chemistry and an interactive terrestrial and oceanic carbon cycle, to investigate whether such components affect the way in which the monsoon changes. We focus particularly on the role of interactive vegetation in the simulations from these model configurations. Using an atmosphere-only HadGEM2 configuration, we investigate how the changes in land cover which result from the interaction between the dynamic vegetation and the model systematic rainfall biases affect the Asian summer monsoon, both in the present-day and in future climate projections. We demonstrate that the response of the dynamic vegetation to biases in regional climate, such as lack of rainfall over tropical dust-producing regions, can affect both the present-day simulation and the response to climate change forcing scenarios.

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Rupp, Philip, et Peter Haynes. « Zonal scale and temporal variability of the Asian monsoon anticyclone in an idealised numerical model ». Weather and Climate Dynamics 2, n^o 2 (6 mai 2021) : 413–31. http://dx.doi.org/10.5194/wcd-2-413-2021.

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Abstract. The upper-level monsoon anticyclone is studied in a 3D dry dynamical model as the response of a background circulation without any imposed zonal structure to a steady imposed zonally confined heat source. The characteristics of the background circulation are determined by thermal relaxation towards a simple meridionally varying state, which gives rise to baroclinic instability if meridional gradients are sufficiently large. This model configuration allows the study of the dependence of the monsoon anticyclone response on characteristics of both the imposed heating and the background state, in particular including interactions between the anticyclone and the active dynamics on its poleward side in the form of a jet and baroclinic eddies. As characteristics of forcing and background state are varied a range of different behaviours emerges, many of which strongly resemble phenomena and features associated with the monsoon anticyclone as observed in re-analysis data. For a resting background state the time-mean anticyclone is highly extended in longitude to the west of the forcing region. When the active mid-latitude dynamics is included the zonal extent of the time-mean anticyclone is limited, without any need for the explicit upper-level momentum dissipation which is often included in simple theoretical models but difficult to justify physically. We further describe in detail the spontaneous emergence of temporal variability in the form of westward eddy shedding from the monsoon anticyclone for varying strength of the imposed heating. By varying the strength of the background mid-latitude dynamics we observe a transition of the system from a state with periodic westward eddy shedding to a state dominated by eastward shedding. The details of the time-mean structure and temporal evolution depend on the structure of the background flow, and for certain flows the monsoon anticyclone shows signs of both westward and eastward shedding.

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Hien, Steffen, Joran Rolland, Sebastian Borchert, Lena Schoon, Christoph Zülicke et Ulrich Achatz. « Spontaneous inertia–gravity wave emission in the differentially heated rotating annulus experiment ». Journal of Fluid Mechanics 838 (10 janvier 2018) : 5–41. http://dx.doi.org/10.1017/jfm.2017.883.

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The source mechanism of inertia–gravity waves (IGWs) observed in numerical simulations of the differentially heated rotating annulus experiment is investigated. The focus is on the wave generation from the balanced part of the flow, a process presumably contributing significantly to the atmospheric IGW field. Direct numerical simulations are performed for an atmosphere-like configuration of the annulus and possible regions of IGW activity are characterised by a Hilbert-transform algorithm. In addition, the flow is separated into a balanced and unbalanced part, assuming the limit of a small Rossby number, and the forcing of IGWs by the balanced part of the flow is derived rigorously. Tangent-linear simulations are then used to identify the part of the IGW signal that is rather due to radiation by the internal balanced flow than to boundary-layer instabilities at the side walls. An idealised fluid set-up without rigid horizontal boundaries is considered as well, to investigate the effect of the identified balanced forcing unmasked by boundary-layer effects. The direct simulations of the realistic and idealised fluid set-ups show a clear baroclinic-wave structure exhibiting a jet–front system similar to its atmospheric counterparts, superimposed by four distinct IGW packets. The subsequent tangent-linear analysis indicates that three wave packets are radiated from the internal flow and a fourth one is probably caused by boundary-layer instabilities. The forcing by the balanced part of the flow is found to play a significant role in the generation of IGWs, so it supplements boundary-layer instabilities as a key factor in the IGW emission in the differentially heated rotating annulus.

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Arteta, J., V. Marécal et E. D. Rivière. « Regional modelling of tracer transport by tropical convection – Part 2 : Sensitivity to model resolutions ». Atmospheric Chemistry and Physics Discussions 9, n^o 2 (4 mars 2009) : 5929–65. http://dx.doi.org/10.5194/acpd-9-5929-2009.

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Abstract. The general objective of this series of two papers is to evaluate long duration limited-area simulations with idealised tracers as a tool to assess the tracer transport in chemistry-transport models (CTMs). In this second paper we analyse the results of three simulations using different horizontal and vertical resolutions against meteorological observations and their impact on idealized tracer transport. The reference simulation (REF) uses a 60 km horizontal resolution and 300 m vertically in the upper troposphere/lower stratosphere (UTLS). A 20 km horizontal resolution simulation (HR) is run as well as a simulation (CVR) with 850 m vertical resolution in the UTLS. The simulations are run for one month during the SCOUT-O3 field campaign. The Falcon and Geophysica aircraft data and the TRMM rainrate estimates have been used to evaluate the simulations. They show that the HR configuration gives generally a better agreement with the measurements than the REF simulation, the CVR simulation giving generally the worst results. The vertical distribution of the tropospheric tracers for the simulations has a similar shape with a 15 km altitude maximum of 0.4 ppbv for REF, 1.2 for HR and 0.04 for CVR. This is related to the dynamics produced by the three simulations that leads to larger values of the upward velocities on average for HR and lower for CVR compared to REF. The HR provides more frequent overshoots over the cold point dynamical barrier than REF and CVR. For the stratospheric tracers the differences between the three simulations are small. The diurnal cycle of the fluxes of all tracers in the TTL (Tropical Tropopause Layer) exhibits a maximum linked to the maximum of convective activity that is particularly well marked in the HR simulation. The largest integrated fluxes are found for tropospheric tracers in HR.

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Arteta, J., V. Marécal et E. D. Rivière. « Regional modelling of tracer transport by tropical convection – Part 2 : Sensitivity to model resolutions ». Atmospheric Chemistry and Physics 9, n^o 18 (24 septembre 2009) : 7101–14. http://dx.doi.org/10.5194/acp-9-7101-2009.

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Abstract. The general objective of this series of two papers is to evaluate long duration limited-area simulations with idealised tracers as a possible tool to assess the tracer transport in chemistry-transport models (CTMs). In this second paper we analyse the results of three simulations using different horizontal and vertical resolutions. The goal is to study the impact of the model spatial resolution on convective transport of idealized tracer in the tropics. The reference simulation (REF) uses a 60 km horizontal resolution and 300 m vertically in the upper troposphere/lower stratosphere (UTLS). A 20 km horizontal resolution simulation (HR) is run as well as a simulation with 850 m vertical resolution in the UTLS (CVR). The simulations are run for one month during the SCOUT-O3 field campaign. Aircraft data, TRMM rainrate estimates and radiosoundings have been used to evaluate the simulations. They show that the HR configuration gives generally a better agreement with the measurements than the REF simulation. The CVR simulation gives generally the worst results. The vertical distribution of the tropospheric tracers for the simulations has a similar shape with a ~15 km altitude maximum for the 6h-lifetime tracer of 0.4 ppbv for REF, 1.2 for HR and 0.04 for CVR. These differences are related to the dynamics produced by the three simulations that leads to larger values of the upward velocities on average for HR and lower for CVR compared to REF. HR simulates more frequent and stronger convection leading to enhanced fluxes compared to REF and higher detrainment levels compared to CVR. HR provides also occasional overshoots over the cold point dynamical barrier. For the stratospheric tracers the differences between the three simulations are small. The diurnal cycle of the fluxes of all tracers in the Tropical Tropopause Layer exhibits a maximum linked to the maximum of convective activity.

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Schwinger, Jörg, Nadine Goris, Jerry F. Tjiputra, Iris Kriest, Mats Bentsen, Ingo Bethke, Mehmet Ilicak, Karen M. Assmann et Christoph Heinze. « Evaluation of NorESM-OC (versions 1 and 1.2), the ocean carbon-cycle stand-alone configuration of the Norwegian Earth System Model (NorESM1) ». Geoscientific Model Development 9, n^o 8 (2 août 2016) : 2589–622. http://dx.doi.org/10.5194/gmd-9-2589-2016.

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Abstract. Idealised and hindcast simulations performed with the stand-alone ocean carbon-cycle configuration of the Norwegian Earth System Model (NorESM-OC) are described and evaluated. We present simulation results of three different model configurations (two different model versions at different grid resolutions) using two different atmospheric forcing data sets. Model version NorESM-OC1 corresponds to the version that is included in the NorESM-ME1 fully coupled model, which participated in CMIP5. The main update between NorESM-OC1 and NorESM-OC1.2 is the addition of two new options for the treatment of sinking particles. We find that using a constant sinking speed, which has been the standard in NorESM's ocean carbon cycle module HAMOCC (HAMburg Ocean Carbon Cycle model), does not transport enough particulate organic carbon (POC) into the deep ocean below approximately 2000 m depth. The two newly implemented parameterisations, a particle aggregation scheme with prognostic sinking speed, and a simpler scheme that uses a linear increase in the sinking speed with depth, provide better agreement with observed POC fluxes. Additionally, reduced deep ocean biases of oxygen and remineralised phosphate indicate a better performance of the new parameterisations. For model version 1.2, a re-tuning of the ecosystem parameterisation has been performed, which (i) reduces previously too high primary production at high latitudes, (ii) consequently improves model results for surface nutrients, and (iii) reduces alkalinity and dissolved inorganic carbon biases at low latitudes. We use hindcast simulations with prescribed observed and constant (pre-industrial) atmospheric CO2 concentrations to derive the past and contemporary ocean carbon sink. For the period 1990–1999 we find an average ocean carbon uptake ranging from 2.01 to 2.58 Pg C yr−1 depending on model version, grid resolution, and atmospheric forcing data set.

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Gladstone, Rupert M., Yuwei Xia et John Moore. « Neutral equilibrium and forcing feedbacks in marine ice sheet modelling ». Cryosphere 12, n^o 11 (22 novembre 2018) : 3605–15. http://dx.doi.org/10.5194/tc-12-3605-2018.

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Abstract. Poor convergence with resolution of ice sheet models when simulating grounding line migration has been known about for over a decade. However, some of the associated numerical artefacts remain absent from the published literature. In the current study we apply a Stokes-flow finite-element marine ice sheet model to idealised grounding line evolution experiments. We show that with insufficiently fine model resolution, a region containing multiple steady-state grounding line positions exists, with one steady state per node of the model mesh. This has important implications for the design of perturbation experiments used to test convergence of grounding line behaviour with resolution. Specifically, the design of perturbation experiments can be under-constrained, potentially leading to a “false positive” result. In this context a false positive is an experiment that appears to achieve convergence when in fact the model configuration is not close to its converged state. We demonstrate a false positive: an apparently successful perturbation experiment (i.e. reversibility is shown) for a model configuration that is not close to a converged solution. If perturbation experiments are to be used in the future, experiment design should be modified to provide additional constraints to the initialisation and spin-up requirements. This region of multiple locally stable steady-state grounding line positions has previously been mistakenly described as neutral equilibrium. This distinction has important implications for understanding the impacts of discretising a forcing feedback involving grounding line position and basal friction. This forcing feedback cannot, in general, exist in a region of neutral equilibrium and could be the main cause of poor convergence in grounding line modelling.

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Allaerts, Dries, et Johan Meyers. « Sensitivity and feedback of wind-farm-induced gravity waves ». Journal of Fluid Mechanics 862 (16 janvier 2019) : 990–1028. http://dx.doi.org/10.1017/jfm.2018.969.

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Flow blockage by large wind farms leads to an upward displacement of the boundary layer, which may excite atmospheric gravity waves in the free atmosphere and on the interface between the boundary layer and the free atmosphere. In the current study, we assess the sensitivity of wind-farm gravity-wave excitation to important dimensionless groups and investigate the feedback of gravity-wave-induced pressure fields to wind-farm energy extraction. The sensitivity analysis is performed using a fast boundary-layer model that is developed to this end. It is based on a three-layer representation of the atmosphere in an idealised barotropic environment, and is coupled with an analytical wake model to account for turbine wake interactions. We first validate the model in two-dimensional mode with data from previous large-eddy simulations of ‘infinitely’ wide wind farms, and then use the model to investigate the sensitivity of wind-farm-induced gravity waves to atmospheric state and wind-farm configuration. We find that the inversion layer induces flow physics similar to shallow-water flow and that the corresponding Froude number plays a crucial role. Gravity-wave excitation is maximal at a critical Froude number equal to one, but the feedback on energy extraction is highest when the Froude number is slightly below one due to a trade-off between amplitude and upstream impact of gravity waves. The effect of surface friction and internal gravity waves is to reduce the flow perturbation and the related power loss by dissipating or dispersing perturbation energy. With respect to the wind-farm configuration, we find that gravity-wave-induced power loss increases with wind-farm size and turbine height. Moreover, we find that gravity-wave effects are small for very wide or very long wind farms and attain a maximum at a width-to-depth ratio of approximately $3/2$.

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Wehner, Michael, Prabhat, Kevin A. Reed, Dáithí Stone, William D. Collins et Julio Bacmeister. « Resolution Dependence of Future Tropical Cyclone Projections of CAM5.1 in the U.S. CLIVAR Hurricane Working Group Idealized Configurations ». Journal of Climate 28, n^o 10 (mai 2015) : 3905–25. http://dx.doi.org/10.1175/jcli-d-14-00311.1.

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The four idealized configurations of the U.S. CLIVAR Hurricane Working Group are integrated using the global Community Atmospheric Model version 5.1 at two different horizontal resolutions, approximately 100 and 25 km. The publicly released 0.9° × 1.3° configuration is a poor predictor of the sign of the 0.23° × 0.31° model configuration’s change in the total number of tropical storms in a warmer climate. However, it does predict the sign of the higher-resolution configuration’s change in the number of intense tropical cyclones in a warmer climate. In the 0.23° × 0.31° model configuration, both increased CO2 concentrations and elevated sea surface temperature (SST) independently lower the number of weak tropical storms and shorten their average duration. Conversely, increased SST causes more intense tropical cyclones and lengthens their average duration, resulting in a greater number of intense tropical cyclone days globally. Increased SST also increased maximum tropical storm instantaneous precipitation rates across all storm intensities. It was found that while a measure of maximum potential intensity based on climatological mean quantities adequately predicts the 0.23° × 0.31° model’s forced response in its most intense simulated tropical cyclones, a related measure of cyclogenesis potential fails to predict the model’s actual cyclogenesis response to warmer SSTs. These analyses lead to two broader conclusions: 1) Projections of future tropical storm activity obtained by a direct tracking of tropical storms simulated by coarse-resolution climate models must be interpreted with caution. 2) Projections of future tropical cyclogenesis obtained from metrics of model behavior that are based solely on changes in long-term climatological fields and tuned to historical records must also be interpreted with caution.

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Hamilton, Kathy, et Beverly A. Wagner. « Commercialised nostalgia ». European Journal of Marketing 48, n^o 5/6 (6 mai 2014) : 813–32. http://dx.doi.org/10.1108/ejm-05-2012-0325.

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Purpose – The purpose of this paper was to develop a framework linking the concept of nostalgia and experiential consumption, articulating the transformation of a mundane activity to a special experience, using the context of the small business and afternoon tea. Design/methodology/approach – The methodology is based on a grounded theory approach and draws on multiple methods of data collection including participant observation, in-depth interviews with afternoon tea room managers, researcher introspection and consumer interviews. Findings – By employing nostalgia cues through product, ritual and aesthetics, an idealised home can be constructed emphasising belonging and sharing. The small business owner can be effective in transforming an ordinary activity to an experiential event. Contemporary tea rooms do not replicate tradition; they use it as a cultural resource to construct something novel. Research limitations/implications – This paper demonstrates how the careful configuration of the retail space can be a key success factor, not only for marketers in large flagship brand stores, but also for smaller, independent and local businesses. The essential interplay between product, ritual and aesthetics creates positive moods of belonging and sharing and may increase satisfaction. Practical implications – Understanding the emotional value of everyday experiences is a point of differentiation in a crowded marketplace and may directly influence consumer loyalty. Staging experiences is a key competitive strategy. Originality/value – This paper is one of the few to empirically assess links between the nostalgia paradigm and experiential consumption. Existing research has emphasised large retail spaces; in contrast, the authors demonstrate how consumer experiences can be staged in smaller, independent and local businesses.

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Eager, Jake K., David J. Reichelt, Nathan J. Mayne, F. Hugo Lambert, Denis E. Sergeev, Robert J. Ridgway, James Manners, Ian A. Boutle, Timothy M. Lenton et Krisztian Kohary. « Implications of different stellar spectra for the climate of tidally locked Earth-like exoplanets ». Astronomy & ; Astrophysics 639 (juillet 2020) : A99. http://dx.doi.org/10.1051/0004-6361/202038089.

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The majority of detected potentially habitable exoplanets orbit stars cooler than the Sun and are therefore irradiated by a stellar spectrum that peaks at longer wavelengths than the spectrum incident on Earth. Here, we present results from a set of simulations of tidally locked terrestrial planets orbiting three different host stars to isolate the effect of the stellar spectra on the simulated climate. Specifically, we perform simulations based on TRAPPIST-1e, adopting an Earth-like atmosphere and using the UK Met Office Unified Model in an idealised ‘aqua-planet’ configuration. Whilst holding the planetary parameters constant, including the total stellar flux (900 W m−2) and orbital period (6.10 Earth days), we compare results between simulations where the stellar spectrum is that of a quiescent TRAPPIST-1, Proxima Centauri, and the Sun. In simulations with cooler host stars, an increased proportion of incident stellar radiation was absorbed directly by the troposphere compared to the surface. This in turn led to an increase in the stability against convection, that is, a reduction in overall cloud coverage on the dayside (reducing scattering), leading to warmer surface temperatures. The increased direct heating of the troposphere also led to more efficient heat transport from the dayside to the nightside and therefore to a reduced day-night temperature contrast. We inferred that planets with an Earth-like atmosphere orbiting cooler stars had lower dayside cloud coverage, potentially allowing habitable conditions at increased orbital radii, compared to similar planets orbiting hotter stars for a given planetary rotation rate.

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Shakespeare, Callum J., et J. R. Taylor. « The spontaneous generation of inertia–gravity waves during frontogenesis forced by large strain : numerical solutions ». Journal of Fluid Mechanics 772 (7 mai 2015) : 508–34. http://dx.doi.org/10.1017/jfm.2015.197.

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A fully nonlinear numerical model is used to investigate spontaneous wave generation during two-dimensional frontogenesis forced by a horizontal strain field. The model uses the idealised configuration of an infinitely long straight front and uniform potential vorticity, with a uniform imposed convergent strain across the front. Shakespeare & Taylor (J. Fluid Mech., vol. 757, 2014, pp. 817–853) formulated a generalised analytical model (ST14) for this system that extends the classical Hoskins & Bretherton (J. Atmos. Sci., vol. 29, 1972, pp. 11–37) model (HB) to large strain rates (${\it\alpha}\sim f$). Here, we use a numerical model to simulate the fully nonlinear problem and compare the results with the predictions of the analytical model for a variety of strain rates. Even for weak strains (${\it\alpha}=0.2f$), the confinement of the secondary circulation and the spontaneous generation of waves, predicted by ST14, are shown to be important corrections to the HB solution. These inviscid predictions are also robust for an equilibrated front where strain-forced frontogenesis is balanced by diffusion. For strong strains the wavefield becomes of leading-order importance to the solution. In this case the frontal circulation is tightly confined, and the vertical velocity is an order of magnitude larger than in the HB model. The addition of a strain field that weakens with time allows the release and propagation of the spontaneously generated waves. We also consider fronts with both large vorticity and strain rate, beyond the validity of the ST14 model.

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Vega, Rubén, et Matthew Kerry. « Nothing Compares to the Past : ». Moving the Social 64 (1 décembre 2020) : 149–75. http://dx.doi.org/10.46586/mts.64.2020.149-175.

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Processes of industrial decline have often generated nostalgia phenomena in the affected communities based on the more or less idealised memory of a past time of prosperity that disappeared as the chimneys went out (‘smokestack nostalgia’, this has been called sometimes). In an earlier time, the development of industries and mining had resulted in the configuration of well-defined social structures and socio-political frameworks. Class identity, collective action, labour disputes and trade union organisations provided the basis on which to build communities that revolved around work. Deindustrialisation undermines both the material and symbolic bases of those cities and regions that have known an industrial boom and exposes them to great uncertainty about their future. The elaboration of a collective memory capable of adapting to a radically transformed context constitutes a research field full of possibilities, despite its complexity. The references can be adapted to new post-industrial scenarios only with considerable difficulty, but at the same time they provide sources of pride and identity and response schemes to adversities. In the following lines, we will concentrate on a specific case: that of Asturias, a mining and industrial region with a prominent role played by the labour movement that has suffered a prolonged decline in its economic bases but has largely managed to preserve social cohesion. The traumatic nature of these changes invites us to explore the way in which collective perceptions manifest themselves and also the role that memory (and oblivion) can play in the reactions of young people subjected to very different challenges from those of their elders.

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Shah, Kasturi, et Peter H. Haynes. « How heating tracers drive self-lofting long-lived stratospheric anticyclones : simple dynamical models ». Weather and Climate Dynamics 5, n^o 2 (22 avril 2024) : 559–85. http://dx.doi.org/10.5194/wcd-5-559-2024.

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Abstract. Long-lived “bubbles” of wildfire smoke or volcanic aerosol have recently been observed in the stratosphere, co-located with ozone, carbon monoxide, and water vapour anomalies. These bubbles often survive for several weeks, during which time they ascend through vertical distances of 15 km or more. Meteorological analysis data suggest that this aerosol is contained within strong, persistent anticyclonic vortices. Absorption of solar radiation by the aerosol is hypothesised to drive the ascent of the bubbles, but the dynamics of how this heating gives rise to a single-sign anticyclonic vorticity anomaly have thus far been unclear. We present a description of heating-driven stratospheric vortices, based on an axisymmetric balanced model. The simplest version of this model includes a specified localised heating moving upwards at fixed velocity and produces a steadily translating solution with a single-signed anticyclonic vortex co-located with the heating, with corresponding temperature anomalies forming a vertical dipole, matching observations. A more complex version includes the two-way interaction between a heating tracer, representing the aerosol, and the dynamics. An evolving tracer provides heating which drives a secondary circulation, and this in turn transports the tracer. Through this two-way interaction an initial distribution of tracer drives a circulation and forms a self-lofting tracer-filled anticyclonic vortex. Scaling arguments show that upward velocity is proportional to heating magnitude, but the magnitude of peak quasigeostrophic vorticity is O(f) (f is the Coriolis parameter) and independent of the heating magnitude. Estimates of vorticity from observations match our theoretical predictions. We discuss 3-D effects such as vortex stripping and dispersion of tracer outside the vortex by the large-scale flow, which cannot be captured explicitly by the axisymmetric model and are likely to be important in the real atmosphere. The large O(f) vorticity of the fully developed anticyclones explains their observed persistence and their effective confinement of tracers. To further investigate the early stages of formation of tracer-filled vortices, we consider an idealised configuration of a homogeneous tracer layer. A linearised calculation reveals that the upper part of the layer is destabilised due to the decrease in tracer concentrations with height there, which sets up a self-reinforcing effect where upward lofting of tracer results in stronger heating and hence stronger lofting. Small amplitude disturbances form isolated tracer plumes that ascend out of the initial layer, indicative of a self-organisation of the flow. The relevance of these idealised models to formation and persistence of tracer-filled vortices in the real atmosphere is discussed, and it is suggested that a key factor in their formation is the time taken to reach the fully developed stage, which is shorter for strong heating rates.

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Shakespeare, Callum J., et J. R. Taylor. « The spontaneous generation of inertia–gravity waves during frontogenesis forced by large strain : theory ». Journal of Fluid Mechanics 757 (26 septembre 2014) : 817–53. http://dx.doi.org/10.1017/jfm.2014.514.

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AbstractDensity fronts are common features of ocean and atmosphere boundary layers. Field observations and numerical simulations have shown that the sharpening of frontal gradients, or frontogenesis, can spontaneously generate inertia–gravity waves (IGWs). Although significant progress has been made in describing frontogenesis using approximations such as quasi-geostrophy (Stone, J. Atmos. Sci., vol. 23, 1966, pp. 455–565, Williams & Plotkin J. Atmos. Sci., vol. 25, 1968, pp. 201–206) semi-geostrophy (Hoskins, Annu. Rev. Fluid Mech., vol. 14, 1982, pp. 131–151), these models omit waves. Here, we further develop the analytical model of Shakespeare & Taylor (J. Fluid Mech., vol. 736, 2013, pp. 366–413) to describe the spontaneous emission of IGWs from an initially geostrophically balanced front subjected to a time-varying horizontal strain. The model uses the idealised configuration of an infinitely long, straight front and uniform potential vorticity (PV) fluid, with a uniform imposed convergent strain across the front, similar to Hoskins & Bretherton (J. Atmos. Sci., vol. 29, 1972, pp. 11–37). Inertia–gravity waves are generated via two distinct mechanisms: acceleration of the large-scale flow and frontal collapse. Wave emission via frontal collapse is predicted to be exponentially small for small values of strain but significant for larger strains. Time-varying strain can also generate finite-amplitude waves by accelerating the cross-front flow and disrupting geostrophic balance. In both cases waves are trapped by the oncoming strain flow and can only propagate away from the frontal zone when the strain field weakens sufficiently, leading to wave emission that is strongly localised in both time and space.

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Mathiot, Pierre, Adrian Jenkins, Christopher Harris et Gurvan Madec. « Explicit representation and parametrised impacts of under ice shelf seas in the <i>z</i><sup>∗</sup> ; coordinate ocean model NEMO 3.6 ». Geoscientific Model Development 10, n^o 7 (26 juillet 2017) : 2849–74. http://dx.doi.org/10.5194/gmd-10-2849-2017.

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Abstract. Ice-shelf–ocean interactions are a major source of freshwater on the Antarctic continental shelf and have a strong impact on ocean properties, ocean circulation and sea ice. However, climate models based on the ocean–sea ice model NEMO (Nucleus for European Modelling of the Ocean) currently do not include these interactions in any detail. The capability of explicitly simulating the circulation beneath ice shelves is introduced in the non-linear free surface model NEMO. Its implementation into the NEMO framework and its assessment in an idealised and realistic circum-Antarctic configuration is described in this study. Compared with the current prescription of ice shelf melting (i.e. at the surface), inclusion of open sub-ice-shelf cavities leads to a decrease in sea ice thickness along the coast, a weakening of the ocean stratification on the shelf, a decrease in salinity of high-salinity shelf water on the Ross and Weddell sea shelves and an increase in the strength of the gyres that circulate within the over-deepened basins on the West Antarctic continental shelf. Mimicking the overturning circulation under the ice shelves by introducing a prescribed meltwater flux over the depth range of the ice shelf base, rather than at the surface, is also assessed. It yields similar improvements in the simulated ocean properties and circulation over the Antarctic continental shelf to those from the explicit ice shelf cavity representation. With the ice shelf cavities opened, the widely used three equation ice shelf melting formulation, which enables an interactive computation of melting, is tested. Comparison with observational estimates of ice shelf melting indicates realistic results for most ice shelves. However, melting rates for the Amery, Getz and George VI ice shelves are considerably overestimated.

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Chung, D., J. P. Monty et N. Hutchins. « Similarity and structure of wall turbulence with lateral wall shear stress variations ». Journal of Fluid Mechanics 847 (23 mai 2018) : 591–613. http://dx.doi.org/10.1017/jfm.2018.336.

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Wall-bounded turbulence, where it occurs in engineering or nature, is commonly subjected to spatial variations in wall shear stress. A prime example is spatially varying roughness. Here, we investigate the configuration where the wall shear stress varies only in the lateral direction. The investigation is idealised in order to focus on one aspect, namely, the similarity and structure of turbulent inertial motion over an imposed scale of stress variation. To this end, we analyse data from direct numerical simulation (DNS) of pressure-driven turbulent flow through a channel bounded by walls of laterally alternating patches of high and low wall shear stress. The wall shear stress is imposed as a Neumann boundary condition such that the wall shear stress ratio is fixed at 3 while the lateral spacing$s$of the uniform-stress patches is varied from 0.39 to 6.28 of the half-channel height$\unicode[STIX]{x1D6FF}$. We find that global outer-layer similarity is maintained when$s$is less than approximately$0.39\unicode[STIX]{x1D6FF}$while local outer-layer similarity is recovered when$s$is greater than approximately$6.28\unicode[STIX]{x1D6FF}$. However, the transition between the two regimes through$s\approx \unicode[STIX]{x1D6FF}$is not monotonic owing to the presence of secondary roll motions that extend across the whole cross-section of the flow. Importantly, these secondary roll motions are associated with an amplified skin-friction coefficient relative to both the small- and large-$s/\unicode[STIX]{x1D6FF}$limits. It is found that the relationship between the secondary roll motions and the mean isovels is reversed through this transition from low longitudinal velocity over low stress at small$s/\unicode[STIX]{x1D6FF}$to high longitudinal velocity over low stress at large$s/\unicode[STIX]{x1D6FF}$.

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Bastianon, Elena, Julie A. Hope, Robert M. Dorrell et Daniel R. Parsons. « Effect of hydro-climate variation on biofilm dynamics and its impact in intertidal environments ». Earth Surface Dynamics 10, n^o 6 (14 novembre 2022) : 1115–40. http://dx.doi.org/10.5194/esurf-10-1115-2022.

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Abstract. Shallow tidal environments are very productive ecosystems but are sensitive to environmental changes and sea level rise. Bio-morphodynamic control of these environments is therefore a crucial consideration; however, the effect of small-scale biological activity on large-scale cohesive sediment dynamics like tidal basins and estuaries is still largely unquantified. This study advances our understanding by assessing the influence of biotic and abiotic factors on biologically cohesive sediment transport and morphology. An idealised benthic biofilm model is incorporated in a 1D morphodynamic model of tide-dominated channels. This study investigates the effect of a range of environmental and biological conditions on biofilm growth and their feedback on the morphological evolution of the entire intertidal channel. By carrying out a sensitivity analysis of the bio-morphodynamic model, parameters like (i) hydrodynamic disturbances, (ii) seasonality, (iii) biofilm growth rate, (iv) temperature variation and (v) bio-cohesivity of the sediment are systematically changed. Results reveal that key parameters such as growth rate and temperature strongly influence the development of biofilm and are key determinants of equilibrium biofilm configuration and development under a range of disturbance periodicities and intensities. Long-term simulations of intertidal channel development demonstrate that the hydrodynamic disturbances induced by tides play a key role in shaping the morphology of the bed and that the presence of surface biofilm increases the time to reach morphological equilibrium. In locations characterised by low hydrodynamic forces, the biofilm grows and stabilises the bed, inhibiting the transport of coarse sediment (medium and fine sand). These findings suggest biofilm presence in channel beds results in intertidal channels that have significantly different characteristics in terms of morphology and stratigraphy compared abiotic sediments. It is concluded that inclusion of bio-cohesion in morphodynamic models is essential to predict estuary development and mitigate coastal erosion.

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SIMSEK, Meliha R. « Using Learner Feedback to Improve Teacher Practices in Materials Adaptation ». Eurasia Proceedings of Educational and Social Sciences 25 (12 décembre 2022) : 9–16. http://dx.doi.org/10.55549/epess.1191899.

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Commercial textbooks are doomed to disappoint user expectations to various extents because irrespective of origin (global/local), they are designed with an idealised classroom in mind, and their prescribed configuration probably won’t be compatible with the ever-diversifying contexts of L2 teaching and learning. Even in the case of a longtime bestseller, EFL teachers may need to customise the student-purchased materials often based on their perceived learning needs, and learner feedback is not as a rule sought on the mostly teacher-led modifications to the textbook content and procedures. Therefore, this study aimed to demonstrate how Maley’s (2011) inputs-processes-outcomes model could be used to evaluate and adapt an intermediate unit on modals of deduction, and examine how a multicultural group of 14 prep students from a major metropolitan state-run university in Turkey reacted to the teacher’s adaptive practices. Descriptive analyses of students’ activity ratings and retrospective reflections demonstrated that the addition of two scaffolded grammar tasks proved better for generating student interest and facilitating learning than replacement of another guessing game with the relatively more open and difficult task on video-based end-of-unit writing activity. Despite being independent users (B1), the participants indicated greater liking for the use of visual aids, ample practice opportunities, collaborative group work, explicit focus on grammar, and learner translations respectively. While their fewer dislikes mainly concerned video quality, activity difficulty and duration, there was almost unanimous agreement that they finally achieved to develop an increased awareness of how to use modality in English. A quick comparison of the 20-item quiz results also showed a considerable increase in their learning gains, for the mean number of correct answers more than doubled from pre- to post-test.

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Mathiot, Pierre, et Nicolas C. Jourdain. « Southern Ocean warming and Antarctic ice shelf melting in conditions plausible by late 23rd century in a high-end scenario ». Ocean Science 19, n^o 6 (22 novembre 2023) : 1595–615. http://dx.doi.org/10.5194/os-19-1595-2023.

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Abstract. How much Antarctic ice shelf basal melt rates can increase in response to global warming remains an open question. Here we describe the response of the Southern Ocean and ice shelf cavities to an abrupt change to high-end atmospheric conditions plausible by the late 23rd century under the SSP5-8.5 scenario. To achieve this objective, we first present and evaluate a new 0.25∘ global configuration of the NEMO (Nucleus for European Modelling of the Ocean NEMO System Team, 2019) ocean and sea ice model. Our present-day simulations demonstrate good agreement with observational data for key variables such as temperature, salinity, and ice shelf melt rates, despite the remaining difficulties to simulate the interannual variability in the Amundsen Sea. The ocean response to the high-end atmospheric perturbation includes a strengthening and extension of the Ross and Weddell gyres and a quasi-disappearance of sea ice, with a subsequent decrease in production of High Salinity Shelf Water and increased intrusion of warmer water onto the continental shelves favoured by changes in baroclinic currents at the shelf break. We propose to classify the perturbed continental shelf as a “warm–fresh shelf”. This induces a substantial increase in ice shelf basal melt rates, particularly in the coldest seas, with a total basal mass loss rising from 1180 to 15 700 Gt yr−1 and an Antarctica averaged melt rate increasing from 0.8 to 10.6 m yr−1. In the perturbed simulation, most ice shelves around Antarctica experience conditions that are currently found in the Amundsen Sea, while the Amundsen Sea warms by 2 ∘C. These idealised projections can be used as a base to calibrate basal melt parameterisations used in long-term ice sheet projections.

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Mirocha, Jeffrey D., Matthew J. Churchfield, Domingo Muñoz-Esparza, Raj K. Rai, Yan Feng, Branko Kosović, Sue Ellen Haupt et al. « Large-eddy simulation sensitivities to variations of configuration and forcing parameters in canonical boundary-layer flows for wind energy applications ». Wind Energy Science 3, n^o 2 (4 septembre 2018) : 589–613. http://dx.doi.org/10.5194/wes-3-589-2018.

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Abstract. The sensitivities of idealized large-eddy simulations (LESs) to variations of model configuration and forcing parameters on quantities of interest to wind power applications are examined. Simulated wind speed, turbulent fluxes, spectra and cospectra are assessed in relation to variations in two physical factors, geostrophic wind speed and surface roughness length, and several model configuration choices, including mesh size and grid aspect ratio, turbulence model, and numerical discretization schemes, in three different code bases. Two case studies representing nearly steady neutral and convective atmospheric boundary layer (ABL) flow conditions over nearly flat and homogeneous terrain were used to force and assess idealized LESs, using periodic lateral boundary conditions. Comparison with fast-response velocity measurements at 10 heights within the lowest 100 m indicates that most model configurations performed similarly overall, with differences between observed and predicted wind speed generally smaller than measurement variability. Simulations of convective conditions produced turbulence quantities and spectra that matched the observations well, while those of neutral simulations produced good predictions of stress, but smaller than observed magnitudes of turbulence kinetic energy, likely due to tower wakes influencing the measurements. While sensitivities to model configuration choices and variability in forcing can be considerable, idealized LESs are shown to reliably reproduce quantities of interest to wind energy applications within the lower ABL during quasi-ideal, nearly steady neutral and convective conditions over nearly flat and homogeneous terrain.

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Whitworth, A. P., et S. E. Jaffa. « A simple approach to CO cooling in molecular clouds ». Astronomy & ; Astrophysics 611 (mars 2018) : A20. http://dx.doi.org/10.1051/0004-6361/201731871.

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Carbon monoxide plays an important role in interstellar molecular clouds, both as a coolant, and as a diagnostic molecule. However, a proper evaluation of the cooling rate due to CO requires a determination of the populations of many levels, the spontaneous and stimulated radiative de-excitation rates between these levels, and the transfer of the emitted multi-line radiation; additionally, this must be done for three isotopologues. It would be useful to have a simple analytic formulation that avoided these complications and the associated computational overhead; this could then be used in situations where CO plays an important role as a coolant, but the details of this role are not the main concern. We derive such a formulation here, by first considering the two asymptotic forms that obtain in the limits of (a) low volume-density and optical depth, and (b) high volume-density and optical depth. These forms are then combined in such a way as to fit the detailed numerical results from Goldsmith & Langer (1978, ApJ, 222, 881; hereafter GL78). The GL78 results cover low temperatures, and a range of physical conditions where the interplay of thermal and sub-thermal excitation, optical-depth effects, and the contributions from rare isotopologues, are all important. The fit is obtained using the Metropolis-Hastings method, and reproduces the results of GL78 well. It is a purely local and analytic function of state — specifically a function of the density, ρ, isothermal sound speed, a, CO abundance, XCO, and velocity divergence, ∇⋅υ. As an illustration of its use, we consider the cooling layer following a slow steady non-magnetic planar J-shock. We show that, in this idealised configuration, if the post-shock cooling is dominated by CO and its isotopologues, the thickness of the post-shock cooling layer is very small and approximately independent of the pre-shock velocity, υo, or pre-shock isothermal sound speed, ao.

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Seki, Kosuke, Keisuke Takeshita et Yoshiharu Amano. « Development of Complex Energy Systems with Absorption Technology by Combining Elementary Processes ». Energies 12, n^o 3 (4 février 2019) : 495. http://dx.doi.org/10.3390/en12030495.

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Optimal design of energy systems ultimately aims to develop a methodology to realize an energy system that utilizes available resources to generate maximum product with minimum components. For this aim, several researches attempt to decide the optimal system configuration as a problem of decomposing each energy system into primitive process elements. Then, they search the optimal combination sequentially from the minimum number of constituent elements. This paper proposes a bottom-up procedure to define and explore configurations by combining elementary processes for energy systems with absorption technology, which is widely applied as a heat driven technology and important for improving system’s energy efficiency and utilizing alternative energy resources. Two examples of application are presented to show the capability of the proposed methodology to find basic configurations that can generate the maximum product. The demonstration shows that the existing absorption systems, which would be calculated based on the experience of designers, could be derived by performing optimization with the synthesis methodology automatically under the simplified/idealized operating conditions. The proposed bottom-up methodology is significant for realizing an optimized absorption system. With this methodology, engineers will be able to predict all possible configurations and identify a simple yet feasible optimal system configuration.

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von der Heydt, Anna, et Henk A. Dijkstra. « Localization of Multidecadal Variability. Part I : Cross-Equatorial Transport and Interbasin Exchange ». Journal of Physical Oceanography 37, n^o 10 (1 octobre 2007) : 2401–14. http://dx.doi.org/10.1175/jpo3133.1.

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Abstract Multidecadal SST variability is studied in idealized one- and two-ocean-basin configurations, using simulations with the Modular Ocean Model. The authors demonstrate that the multidecadal variability on the global “conveyor type” circulation is localized in the North Atlantic Ocean. Interbasin exchange processes determine the locations where regions of deep-water formation occur and induce a localization of SST multidecadal anomalies in the Atlantic. The physics of this localization is subsequently investigated by considering more equatorially symmetric background flows in two-basin and one-basin configurations. A cross-equatorial flow in the Atlantic induces the localization of the multidecadal variability in the North Atlantic. By using the mechanism of multidecadal variability as proposed in 2002 by Te Raa and Dijkstra in a single-hemispheric configuration, the physics of these localization processes can be explained.

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LECLERC, G. « Idealized line source configuration for permanent 125I prostate implants ». Radiotherapy and Oncology 72, n^o 2 (août 2004) : 213–20. http://dx.doi.org/10.1016/j.radonc.2004.04.001.

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Kanai, Akane, et Amy Dobson. « Making do on not much : High Energy Striving, Femininity and Friendship in Broad City ». Culture Unbound 11, n^o 3-4 (30 janvier 2020) : 517–33. http://dx.doi.org/10.3384/cu.2000.1525.19v11a28.

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In the years following the 2008 global financial crisis (“GFC”), feminist media scholarship has drawn attention to the gendered calls in Western media culture to remake subjectivity in line with imperatives of thrift required in conditions of austerity. In the shared symbolic environments that “gender the recession” (Negra & Tasker, 2014), media ranging from news, reality television, and film have placed further, intensified demands on women’s domestic, affective, paid and unpaid labour, requiring attitudinal orientations combining future-oriented enthusiasm, positivity, entrepreneurialism, a continued faith in (budget-conscious) consumption and investment in the home and the family. This article considers the US comedy Broad City as an articulation of how young women are critically grappling with such shifts in gendered social relations and labour markets in the cosmopolitan setting of New York City. We suggest, in the depiction of the central female friendship between Abbi Abrams (Abbi Jacobson) and Ilana Wexler (Ilana Glazer) in Broad City, the show foregrounds the necessity of young women’s “high energy striving” but produces an alternative configuration of the normative relation between femininity and labour. In the show, contra the “retreatism” Negra and Tasker document idealising women’s work in the home as a means of combatting an austere future, the thrifty fun, care, support, and love Abbi and Ilana strive to create together spills across public spaces, spanning the streets of the city, outdoors in parks and on stoops. Abbi and Ilana are continually depicted labouring in some way, though such labour does not generally result in financial or career-based reward, but rather, produces psychic and emotional sustenance for the women’s friendship and a means of affectively investing in each other. Thus, in Broad City’s acknowledgement of the high energy striving required to survive, the show critically questions the relation of such feminine striving to the promise of career, financial success, and the idealised direction of such striving towards the domestic and hetero-patriarchal family. Instead, the show emphasises the material importance of such striving in relation to the bonds of women’s friendship in conditions of material and social hardship, suggesting a different orientation to women’s work and its place in recessional culture.

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Patrikalakis, N. M., T. Maekawa, G. A. Kriezis et H. N. Gursoy. « Theoretical and Experimental Prediction of the Response of Compliant Risers ». Journal of Offshore Mechanics and Arctic Engineering 112, n^o 3 (1 août 1990) : 244–52. http://dx.doi.org/10.1115/1.2919863.

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The general three-dimensional linearized dynamic equations of a compliant riser, idealized as a rotationally nonuniform rod, around a nonlinear static configuration in the presence of general current and monochromatic wave excitation are formulated. Nonlinear forces such as quadratic drag are harmonically linearized by minimizing the mean square error between the linear approximation and the nonlinear force. The theory is implemented in a computer program which allows analysis of a variety of compliant riser configurations. Numerical examples for catenary risers are included. Comparisons of our theoretical predictions with experimental results obtained from a 1.5-m catenary compliant riser model excited monochromatically at the top parallel to a constant current are also presented to evaluate our ability to predict the response of compliant riser systems.

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Morrison, H. « On the robustness of aerosol effects on an idealized supercell storm simulated with a cloud system-resolving model ». Atmospheric Chemistry and Physics 12, n^o 16 (23 août 2012) : 7689–705. http://dx.doi.org/10.5194/acp-12-7689-2012.

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Abstract. A cloud system-resolving model (the Weather Research and Forecasting model) with 1 km horizontal grid spacing is used to investigate the response of an idealized supercell storm to increased cloud droplet concentrations associated with polluted conditions. The primary focus is on exploring robustness of simulated aerosol effects in the face of complex process interactions and feedbacks between the cloud microphysics and dynamics. Simulations are run using sixteen different model configurations with various microphysical or thermodynamic processes modified or turned off. Robustness of the storm response to polluted conditions is also explored for each configuration by performing additional simulations with small perturbations to the initial conditions. Differences in the domain-mean accumulated surface precipitation and convective mass flux between polluted and pristine conditions are small for almost all model configurations, with relative differences in each quantity generally less than 15%. Configurations that produce a decrease (increase) in cold pool strength in polluted conditions also tend to simulate a decrease (increase) in surface precipitation and convective mass flux. Combined with an analysis of the dynamical and thermodynamic fields, these results indicate the importance of interactions between microphysics, cold pool evolution, and dynamics along outflow boundaries in explaining the system response. Several model configurations, including the baseline, produce an overall similar storm response (weakening) in polluted conditions despite having different microphysical or thermodynamic processes turned off. With hail initiation turned off or the hail fallspeed-size relation set to that of snow, the model produces an invigoration instead of weakening of the storm in polluted conditions. These results highlight the difficulty of foreseeing impacts of changes to model parameterizations and isolating process interactions that drive the system response to aerosols. Overall, these findings are robust, in a qualitative sense, to small perturbations in the initial conditions. However, there is sensitivity in the magnitude, and in some cases sign, of the storm response to polluted conditions with small perturbations in the temperature of the thermal used to initiate convection (less than &pm;0.5 K) or the vertical shear of the environmental wind (&pm;5%). It is concluded that reducing uncertainty in simulations of aerosol effects on individual deep convective storms will likely require ensemble methods in addition to continued improvement of model parameterizations.

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Bateson, Adam William, Daniel L. Feltham, David Schröder, Yanan Wang, Byongjun Hwang, Jeff K. Ridley et Yevgeny Aksenov. « Sea ice floe size : its impact on pan-Arctic and local ice mass and required model complexity ». Cryosphere 16, n^o 6 (28 juin 2022) : 2565–93. http://dx.doi.org/10.5194/tc-16-2565-2022.

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Abstract. Sea ice is composed of discrete units called floes. Observations show that these floes can adopt a range of sizes spanning orders of magnitude, from metres to tens of kilometres. Floe size impacts the nature and magnitude of interactions between the sea ice, ocean, and atmosphere including lateral melt rate and momentum and heat exchange. However, large-scale geophysical sea ice models employ a continuum approach and traditionally either assume floes adopt a constant size or do not include an explicit treatment of floe size. In this study we apply novel observations to analyse two alternative approaches to modelling a floe size distribution (FSD) within the state-of-the-art CICE sea ice model. The first model considered is a prognostic floe size–thickness distribution where the shape of the distribution is an emergent feature of the model and is not assumed a priori. The second model considered, the WIPoFSD (Waves-in-Ice module and Power law Floe Size Distribution) model, assumes floe size follows a power law with a constant exponent. We introduce a parameterisation motivated by idealised models of in-plane brittle fracture to the prognostic model and demonstrate that the inclusion of this scheme enables the prognostic model to achieve a reasonable match against the novel observations for mid-sized floes (100 m–2 km). While neither FSD model results in a significant improvement in the ability of CICE to simulate pan-Arctic metrics in a stand-alone sea ice configuration, larger impacts can be seen over regional scales in sea ice concentration and thickness. We find that the prognostic model particularly enhances sea ice melt in the early melt season, whereas for the WIPoFSD model this melt increase occurs primarily during the late melt season. We then show that these differences between the two FSD models can be explained by considering the effective floe size, a metric used to characterise a given FSD. Finally, we discuss the advantages and disadvantages to these different approaches to modelling the FSD. We note that although the WIPoFSD model is unable to represent potentially important features of annual FSD evolution seen with the prognostic model, it is less computationally expensive and produces a better fit to novel FSD observations derived from 2 m resolution MEDEA imagery, possibly making this a stronger candidate for inclusion in climate models.

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Morrison, H. « On the robustness of aerosol effects on an idealized supercell storm simulated with a cloud system-resolving model ». Atmospheric Chemistry and Physics Discussions 12, n^o 4 (24 avril 2012) : 10493–533. http://dx.doi.org/10.5194/acpd-12-10493-2012.

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Abstract. A cloud system-resolving model (the Weather Research and Forecasting model) with 1 km horizontal grid spacing is used to investigate the response of an idealized supercell storm to increased cloud droplet concentrations associated with polluted conditions. The primary focus is on exploring robustness of simulated aerosol effects in the face of complex process interactions and feedbacks between the cloud microphysics and dynamics. Simulations are run using sixteen different model configurations with various microphysical or thermodynamic processes modified or turned off. Robustness of the storm response to polluted conditions is also explored for each configuration by performing additional simulations with small perturbations to the initial conditions. Differences in the domain-mean accumulated surface precipitation and convective mass flux between polluted and pristine conditions are small for almost all model configurations, with relative differences in each quantity generally less than 15%. Configurations that produce a decrease (increase) in cold pool strength in polluted conditions also tend to simulate a decrease (increase) in surface precipitation and convective mass flux. Combined with an analysis of the dynamical and thermodynamic fields, these results indicate the importance of interactions between microphysics, cold pool evolution, and dynamics along outflow boundaries in explaining the system response. Several model configurations, including the baseline, produce an overall similar storm response (weakening) in polluted conditions despite having different microphysical or thermodynamic processes turned off. This occurs because of compensation by other process interactions, illustrating network-like behavior of the system. These results highlight the difficulty of foreseeing impacts of changes to model parameterizations and isolating process interactions that drive the system response to aerosols. With hail initiation turned off or the hail fallspeed-size relation set to that of snow, the model produces an invigoration instead of weakening of the storm in polluted conditions. Overall, these findings are robust, in a qualitative sense, to small perturbations in the initial conditions. However, there is sensitivity in the magnitude, and in some cases sign, of the storm response to polluted conditions with small perturbations in the temperature of the thermal used to initiate convection (less than ±0.5 K) or the vertical shear of the environmental wind (±5%). It is concluded that reducing uncertainty in simulations of aerosol effects on individual deep convective storms will likely require ensemble methods in addition to continued improvement of model parameterizations.

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RAMEZANPOUR, MEHDI, MEHDI MAEREFAT, NAHID RAMEZANPOUR, MANIJHE MOKHTARI-DIZAJI, FARIDEH ROSHANALI et FARHAD RIKHTEGAR NEZAMI. « NUMERICAL INVESTIGATION OF THE EFFECTS OF BED SHAPE ON THE END-TO-SIDE CABG HEMODYNAMICS ». Journal of Mechanics in Medicine and Biology 19, n^o 04 (juin 2019) : 1950019. http://dx.doi.org/10.1142/s0219519419500192.

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Disrupted flow initiates and aggravates intimal thickening in the end-to-side (ETS) coronary artery bypass grafting (CABG), which may lead to failure. To enhance the post-intervention hemodynamics, the geometry is either optimized or totally reconfigured. Majority of configurations proposed by researchers have not suited CABG surgery, for they entailed rigorous manipulation on conventional grafts in situ, which was neither swift nor straightforward. The aim of the present study is, thus, to introduce a slight, yet effective, modification to a conventional ETS CABG configuration, and numerically investigate its effects on updated hemodynamic and structural environment, anticipating the longevity of proposed configuration and CABG success. This fairly simple modification may easily be made positioning a pre-designed anastomotic device between the bed of host artery in the conventional ETS CABG and its surrounding tissues. Conducting comprehensive numerical simulations, performance of the proposed configuration was assessed using idealized and patient-specific geometries of the conventional ETS CABG. Blood flow was simulated in a conventional and an updated CABG configuration considering 2-way fluid–structure interaction. Results revealed that, although the proposed configuration may induce higher structural stresses in vessels walls, it may improve important hemodynamic metrics such as wall shear stress gradient, oscillatory shear index, and relative residence time on host artery bed reducing disruption of flow. This study may also set the stage for design engineers and regulatory officials to evolve ETS CABG toward more hemodynamics-friendly approaches. Further in vitro, preclinical, and clinical experiments are, yet, entailed to accomplish ideal designs of procedural guidelines/grafts.

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HA, Kyung-Ja. « A Brief Study on the Achievement of Syukuro Manabe, Awardee of 2021 Nobel Prize in Physics ». Physics and High Technology 30, n^o 12 (31 décembre 2021) : 10–15. http://dx.doi.org/10.3938/phit.30.038.

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Manabe Syukuro is well known as a father of climate modeling. He and his colleagues have achieved several important milestones in the research on global warming. In this article, two highly advanced subjects are described. In the early 1960s, he developed a radiative-convective model of the atmosphere and explored the role of greenhouse gases, such as water vapor, carbon dioxide, and ozone in maintaining and changing the thermal structure of the atmosphere. His study was the beginning of long-term research on global warming. In 1969, Manabe and Bryan published the first results from a coupled ocean-atmosphere general circulation model (OAGCM). However, this model used a highly idealized continent-ocean configuration. Results from the first coupled OAGCM with more realistic configurations were published in 1975, which eventually became a very powerful tool for the simulation of global warming.

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Meliande, Natalin Michele, Michelle Souza Oliveira, Pedro Henrique Poubel Mendonça da Silveira, Rafael Rodrigues Dias, Rubens Lincoln Santana Blazutti Marçal, Sergio Neves Monteiro et Lucio Fabio Cassiano Nascimento. « Curaua–Aramid Hybrid Laminated Composites for Impact Applications : Flexural, Charpy Impact and Elastic Properties ». Polymers 14, n^o 18 (8 septembre 2022) : 3749. http://dx.doi.org/10.3390/polym14183749.

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Curaua, as a leaf-based natural fiber, appears to be a promising component with aramid fabric reinforcement of hybrid composites. This work deals with the investigation of flexural, impact and elastic properties of non-woven curaua–aramid fabric hybrid epoxy composites. Five configurations of hybrid composites in a curaua non-woven mat with an increasing quantity of layers, up to four layers, were laminated through the conventional hand lay-up method. The proposed configurations were idealized with at least 60 wt% reinforcement in the non-alternating configuration. As a result, it was observed that the flexural strength decreased by 33% and the flexural modulus by 56%. In addition, the energy absorbed in the Charpy impact also decreased in the same proportion as the replaced amount of aramid. Through the impulse excitation technique, it was possible observe that the replacement of the aramid layers with the curaua layers resulted in decreased elastic properties. However, reduction maps revealed proportional advantages in hybridizing the curaua with the aramid fiber. Moreover, the hybrid composite produced an almost continuous and homogeneous material, reducing the possibility of delamination and transverse deformation, which revealed an impact-resistant performance.

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Schultz, David M., Jonathan G. Fairman, Stuart Anderson et Sharon Gardner. « Build Your Own Earth : A Web-Based Tool for Exploring Climate Model Output in Teaching and Research ». Bulletin of the American Meteorological Society 98, n^o 8 (1 août 2017) : 1617–23. http://dx.doi.org/10.1175/bams-d-16-0121.1.

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Abstract Build Your Own Earth was designed as a web-based tool for the user to select various characteristics of a planet and see what the climate of that planet would be like. Because of the limitations of computer resources, presimulated Earths were run using the Fast Ocean Atmosphere Model at relatively coarse resolution. The tool provides 50 different Earth configurations in three categories: Recent, Ancient, and Alien Earths. Recent Earths fix the continental configuration at the present day and vary the axial tilt, eccentricity, and greenhouse gas concentrations. Ancient Earths include a series of paleoclimate simulations from the Last Glacial Maximum 21,000 years ago to the Ediacaran 600 million years ago. Alien Earths include an aquaplanet, terraplanet, ice planet, and various idealized continental configurations. Fifty different monthly averaged quantities are available to view in an annual cycle from four different map projections. Build Your Own Earth was built and designed for a massive open online course, but it has also been used in the classroom at the University of Manchester, as well as research projects on paleoclimate and planetary habitability, for example. The tool is freely available online (www.buildyourownearth.com) for anyone to access.

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Suárez de la Torre, Emilio. « Sicilia en Píndaro : Insula Fortunata ». Fortunatae. Revista Canaria de Filología, Cultura y Humanidades Clásicas, n^o 34 (2021) : 187–204. http://dx.doi.org/10.25145/j.fortunat.2021.34.10.

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Hundt, R., J. Christian Scho¨n, A. Hannemann et M. Jansen. « Determination of symmetries and idealized cell parameters for simulated structures ». Journal of Applied Crystallography 32, n^o 3 (1 juin 1999) : 413–16. http://dx.doi.org/10.1107/s0021889898015763.

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A robust algorithm is presented that determines the symmetries present in an atomic configuration and idealizes the cell parameters according to the crystal system suggested by the symmetries detected. No information besides the coordinates of the atoms within some arbitrary unit cell of the crystal is required.

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Archer, D. E., et B. A. Buffett. « A two-dimensional model of the methane cycle in a sedimentary accretionary wedge ». Biogeosciences 9, n^o 8 (24 août 2012) : 3323–36. http://dx.doi.org/10.5194/bg-9-3323-2012.

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Abstract. A two-dimensional model of sediment column geophysics and geochemistry has been adapted to the problem of an accretionary wedge formation, patterned after the margin of the Juan de Fuca plate as it subducts under the North American plate. Much of the model description is given in a companion paper about the application of the model to an idealized passive margin setting; here we build on that formulation to simulate the impact of the sediment deformation, as it approaches the subduction zone, on the methane cycle. The active margin configuration of the model shares sensitivities with the passive margin configuration, in that sensitivities to organic carbon deposition and respiration kinetics, and to vertical bubble transport and redissolution in the sediment, are stronger than the sensitivity to ocean temperature. The active margin simulation shows a complex sensitivity of hydrate inventory to plate subduction velocity, with results depending strongly on the geothermal heat flux. In low heat-flux conditions, the model produces a larger inventory of hydrate per meter of coastline in the passive margin than active margin configurations. However, the local hydrate concentrations, as pore volume saturation, are higher in the active setting than in the passive, as generally observed in the field.

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de Grandpré, Jean, Monique Tanguay, Abdessamad Qaddouri, Mohamed Zerroukat et Chris A. McLinden. « Semi-Lagrangian Advection of Stratospheric Ozone on a Yin–Yang Grid System ». Monthly Weather Review 144, n^o 3 (19 février 2016) : 1035–50. http://dx.doi.org/10.1175/mwr-d-15-0142.1.

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Abstract The lack of formal mass conservation that is inherent to the standard semi-Lagrangian transport scheme represents a significant model limitation that needs to be addressed. The magnitude of this impact depends on the nature of the advected quantity and particularly on the strength of species spatiotemporal variability. In this study, this issue is examined in the context of two configurations of the Environment Canada Global Environmental Multiscale (GEM) model. The first configuration (GEM Lat–Lon) is based on a global latitude–longitude grid system with the Arakawa C grid in the horizontal. The second configuration (GEM Yin–Yang) uses the overset Yin–Yang grid, which is singularity free and has quasi-uniform resolution. Both model versions have been used for studying the mass conservation property of passive and nonpassive tracers such as stratospheric ozone using different shape-preserving schemes and a global mass fixer. Experiments with idealized tracers indicate that the implementation of a global mass fixer and a conservative shape-preserving scheme reduces the error field in both 2D and 3D configurations. In the case of stratospheric ozone, the study demonstrates that the mass conservation error is significantly reduced with the use of the Yin–Yang grid. This is attributed to the quasi-uniform nature of the grid that contributes to improve the accuracy of the computation particularly in high-latitude regions where most of the ozone mass resides. The study demonstrates the potential benefits of using a quasi-uniform Yin–Yang grid system and shows that chemical constituents can serve as a useful diagnostic for the evaluation of numerical weather prediction (NWP) models.

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