Decadal Climate Variability in Mesoscale-resolving Coupled Models

Most of our knowledge about the causes of 20th-century climate change comes from simulation using numerical models. However, the observed climate variability and the one simulated by the state-of-the-art climate models exhibit substantial discrepancies at the decadal-to-multidecadal time scale and thus it hinders our fundamental understanding of the observed climate change. Evidence is mounting that vigorous intrinsic variability associated with mesoscale oceanic features contributes significantly to large-scale low-frequency climate variability, with fundamental implications for decadal climate low-frequency climate prediction. As of yet, extensive simulation of these decadal effects using high-resolution state-of-the-art coupled climate models has been computationally prohibitive, as it may require mesoscale-resolving atmospheric components. Here we study the effects of mesoscale air-sea coupling on large-scale low-frequency (interannual-to-multidecadal) climate variability using idealized high-resolution coupled climate models.We hypothesized that resolving mesoscale oceanic fronts and eddies in both ocean and atmosphere will lead to the emergence of qualitatively new phenomena rooted, dynamically, in multi-scale ocean-atmosphere interactions. In particular, we propose that the climate system may possess internal climate modes due to multi-scale ocean–atmosphere interactions involving (i) decadal variations in the meridional location and magnitude of the narrow (mesoscale, 100-km wide) sea-surface temperature (SST) fronts associated with the eastward-jet extension of oceanic western boundary currents (such as Gulf Stream); (ii) mesoscale response of the atmospheric planetary boundary layer (APBL) winds and, most importantly, ensuing large-scale (basin-scale-to-global-scale) response of the free atmosphere to these mesoscale SST anomalies; and (iii) subsequent modifications in the large-scale oceanic wind-driven gyres and further changes in the location and/or magnitude of the SST fronts. The unambiguous demonstration of a concerted action of these elements to result in the coherent decadal and longer internal climate variability has yet remained elusive, partly because modeling these dynamics requires at least semi-hemispheric-extent coupled ocean–atmosphere climate models with high horizontal resolution in both fluids; long, multidecadal simulations using these models are challenging to achieve due to their enormous computational expense. The goal of the present work was to test our hypothesis above in a more idealized, numerically efficient model, yet the one containing the requisite dynamics required in the elements (i), (ii), (iii) of the proposed multi-scale coupled decadal climate modes. The model versions we developed and used here are based on the Quasi-Geostrophic Coupled Model (Q-GCM) of Hogg et al. (2003, 2006, 2009, 2014), which was revamped and modified to include a parameterized effect of SST anomalies on APBL wind, a new radiation/heat exchange parameterization meant to invigorate the coupling between the surface and free atmosphere, and, finally, the moisture dynamics and the associated latent heat sources that are likely to be essential in the large-scale atmospheric response to mesoscale SST anomalies; the moist model version was dubbed the MQ-GCM model. Despite these modifications, we have to report that we did not thus far identify, in this model, the parameter regime conducive to the multi-scale coupled ocean–atmosphere modes we were looking for. The two main stumbling blocks we encountered were the inability of the ocean model to produce persistent self-sustained meridional shifts of the midlatitude SST front implied in (i), and the weak forced response of the model’s free atmosphere to variable SST fronts, even in the MQ-GCM model, which affects leg (ii) of the proposed feedback sequence. We used the insights obtained during the project to propose a set of suggestions for future work needed to rectify these issues

Further Remarks on Stochastic Damage Evolution of Brittle Solids Under Dynamic Tensile Loading

This article illuminates some general features and provides elementary interpretations of the deformation, damage, and failure of brittle solids characterized by very low fracture energy. The dynamic response of these materials is determined to a large extent by stochastic and random factors. The investigation emphasis is on the moderate-to-extremely high rate range (10 s 1, 1 109 s 1), explored under practically identical in-plane stress conditions. The statistical approach is based on repeated particle dynamics simulations for different physical realizations of micromechanical disorder of a 2D brittle discrete system. The proposed strategy is computationally intensive, which necessitates simplicity of the laws governing the interparticular interaction. Based on the simulation results, an expression is proposed to model the mean tensile strength dependence on the strain rate. The linearity of the rate dependence of the stress-peak macroscopic response parameters is observed and discussed

STRUCTURAL CALCULATION OF AN EMPLACEMENT PALLET STATICALLY LOADED BY A WASTE PACKAGE

The purpose of this calculation is to determine the structural response of the emplacement pallet (EP) subjected to static load from the mounted waste package (WP). The scope of this document is limited to reporting the calculation results in terms of stress intensity magnitudes. This calculation is associated with the waste emplacement systems design; calculations are performed by the Waste Package Design group. AP-3.12Q, Revision 0, ICN 0, Calculations, is used to perform the calculation and develop the document. The finite element solutions are performed by using the commercially available ANSYS Version (V) 5.4 finite element code. The results of these calculations are provided in terms of maximum stress intensity magnitudes

A Note on Short-time Response of Two-dimensional Lattices during Dynamic Loading

The disordered 2D lattices are used extensively to study damage evolution and fracture of inhomogeneous or multi-phase systems. The present note addresses their initial elastic response during dynamic loading. Namely, a transition from short-time values of modulus of elasticity and Poisson’s ratio to respective long-time values, which is not accompanied by the corresponding change of stiffness tensor components. The study is performed on three 2D truss-type lattices. It is demonstrated that the difference between the two sets of elastic properties is a result of combining effects of the initial lateral inertia and the disorder of the system.Основни подаци у наставку (отворени приступ, CC0 Public Domain, copyright: Сретен Мастиловић) односе се на рецензирану (accepted) верзију рада која ће бити депонована у овом запису

Drop Calculations of HLW Canister and Pu Can-in-Canister

The objective of this calculation is to determine the structural response of the standard high-level waste (HLW) canister and the canister containing the cans of immobilized plutonium (Pu) (''can-in-canister'' [CIC] throughout this document) subjected to drop DBEs (design basis events) during the handling operation. The evaluated DBE in the former case is 7-m (23-ft) vertical (flat-bottom) drop. In the latter case, two 2-ft (0.61-m) corner (oblique) drops are evaluated in addition to the 7-m vertical drop. These Pu CIC calculations are performed at three different temperatures: room temperature (RT) (20 C ), T = 200 F = 93.3 C , and T = 400 F = 204 C ; in addition to these the calculation characterized by the highest maximum stress intensity is performed at T = 750 F = 399 C as well. The scope of the HLW canister calculation is limited to reporting the calculation results in terms of: stress intensity and effective plastic strain in the canister, directional residual strains at the canister outer surface, and change of canister dimensions. The scope of Pu CIC calculation is limited to reporting the calculation results in terms of stress intensity, and effective plastic strain in the canister. The information provided by the sketches from Reference 26 (Attachments 5.3,5.5,5.8, and 5.9) is that of the potential CIC design considered in this calculation, and all obtained results are valid for this design only. This calculation is associated with the Plutonium Immobilization Project and is performed by the Waste Package Design Section in accordance with Reference 24. It should be noted that the 9-m vertical drop DBE, included in Reference 24, is not included in the objective of this calculation since it did not become a waste acceptance requirement. AP-3.124, ''Calculations'', is used to perform the calculation and develop the document

Vertical Drop of the Naval SNF Long Waste Package On Unyielding Surface

The purpose of this calculation is to determine the structural response of a Naval SNF (Spent Nuclear Fuel) Long Waste Package (WP) subjected to 2 m-vertical drop on unyielding surface (US). The scope of this document is limited to reporting the calculation results in terms of maximum stress intensities. This calculation is associated with the waste package design; calculation is performed by the Waste Package Design group. AP-3.12Q, Revision 0, ICN 0, Calculations, is used to perform the calculation and develop the document. The finite element calculation is performed by using the commercially available ANSYS Version (V) 5.4 finite element code. The result of this calculation is provided in terms of maximum stress intensities

STRUCTURAL CALCULATIONS FOR THE CODISPOSAL OF TRIGA SPENT NUCLEAR FUEL IN A WASTE PACKAGE

The purpose of this analysis is to determine the structural response of a TRIGA Department of Energy (DOE) spent nuclear fuel (SNF) codisposal canister placed in a 5-Defense High Level Waste (DHLW) waste package (WP) and subjected to a tipover design basis event (DBE) dynamic load; the results will be reported in terms of displacements and stress magnitudes. This activity is associated with the WP design

Damage-fragmentation transition: Size effect and scaling behavior for impact fragmentation of slender projectiles

The focus of the present article is on the size effect of a transition region from the damaged to the fragmented phase in impact-induced breakup of a slender projectile. Molecular dynamics simulations of the classic ballistic Taylor test are performed with a simple generic model to explore an extended low energy range. In the simulation setup, flat-ended, monocrystalline, nanoscale projectiles, with a fixed aspect ratio but 10 different diameters, collide perpendicularly with a rough rigid wall. With gradually increasing impact energy, a non-negligible projectile disintegration eventually takes place and is identified with the damage-fragmentation phase transition. These atomistic simulations offer an indispensable tool to gain an insight into damage evolution in the neighborhood of the damage-fragmentation transition resulting in the occurrence of fragmentation at the critical point. A finite size scaling analysis of the average fragment mass is carried out to determine critical exponents and dependence of the critical striking velocity upon the slender projectile’s diameter

Some Observations Regarding Stochasticity of Dynamic Response of 2D Disordered Brittle Lattices

It had been long recognized that the tensile strength of brittle materials increases with increase of the loading rate. In the present article, a statistical approach to rupture of a disordered 2D triangular truss lattice consisting of fragile nonlinear springs is attempted in hope to elucidate some generic effects of structural and geometrical disorder on the tensile strength and the (stress-peak and post-peak) damage energy rates. The simulation results reveal increase of the mean and decrease of the standard deviation of the macroscopic tensile strength with increase of the structural and geometrical order till the ‘theoretical strength’ saturation. At the same time, the increase in lattice disorder results in increase of the mean and standard deviation of the stress-peak damage energy rate, followed by the decrease of the same in the softening regime