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This article revisits Brechtian tragedy through a posthumanist reading framed through reference, particularly, to the work of N. Katherine Hayles, doing so in the context of broader questions about how genres decline (e.g. the pastoral, the georgic, the epic though not, inevitably, the tragic). The de-centring of humanistic assumptions and practices would seem to invite a re-visioning of the tragic, one shorn of traditional generic and affective certainties, and attentive to new technological imperatives.

The Charney–Phillips grid, used in many numerical models of the atmosphere, involves vertically staggering the nodes of the density variable with the nodes of the entropy-type variable. When moisture is included in such a model, it is either co-located with density so that moisture can be transported conservatively and consistently with dry mass, or with the entropy-type variable so that the coupling between moisture and temperature can be represented well. Both properties are desirable, yet at first it appears difficult to obtain both simultaneously. Here, we present a framework to resolve this problem, by co-locating the moisture mixing ratio with potential temperature but formulating its transport as that of a density on a vertically shifted mesh. Within this framework, particular choices of the operators involved provide the desired conservation and consistency properties of the moisture transport. The framework is described in the context of a finite-element approach. We also present an explicit Runge–Kutta time-stepping scheme that is appropriate for use within this framework. This approach is then illustrated through numerical tests, which demonstrate that it does indeed have the desired conservation and consistency properties.

Definitions of digital abound at the present time, but there is a thread amongst the most vital of these that questions the relevance of human agency and evaluative choice. If we follow where technological advances take us we come to the unsettling conclusion that ‘machine reading’ has usurped more analogue procedures and that algorithmic formulae have supplanted human judgement; the opportunities that new software provide can outstrip our imagination in framing research questions. Literary history, however, addresses how we might make sense of the One as well as the Many, and, when confronted by a string of word- or phrase-patterns, it is not that our findings speak for themselves; we have to conjure their value. This is exemplified by analysing where some digital searches might take us in relation to Shakespeare's The Merchant of Venice, basing the reading on all the repetitions of gentile/ gentle, kind, and credit. The sensitive interrogation of the play's electronic text does point us to salient ‘returns’ and patterning signalled by following where the significant iterations of these words might take us, but what we make of these lines of enquiry eventually calls on human evaluation and volition.

In October 2017 an advertisement appeared on ebay for an old cast-iron “double-cone” throwing wheel, thought to have been used by the potter William Staite Murray (1881–1962). Murray was a leading ...

The Research Software Engineer Knowledge IntegrationLandscape Review was written by the ExCALIBUR Programme Community. It documents the concept of the Research Software Engineer (RSE) and their role in many of todays computational science projects.The reviewprovides a comprehensive review of the skills required by Research Software Engineersin HPC and their future training needs

In an numerical weather prediction (NWP) model, the complex interplay, in a rotating frame of reference, between the winds, the highs and lows of pressure, and the transport of mass and thermal energy are the responsibility of the dynamical core. A recent review lists 26 existing NWP dynamical cores. So why, after more than 50 years of operational NWP, does there remain such a plethora of dynamical cores with little hint of convergence in the choice of which schemes to use? Indeed, as the architectures of supercomputers are on the brink of changing significantly, what convergence there might have been seems set to dissipate. The same review lists 28 models under development. By exploring some of the physical properties of the equations that lie at the heart of the dynamical core and revealing the challenges for the numerical schemes used to discretize those equations, this chapter attempts to uncover some of the reasons for this uncertain landscape in such a critical component of NWP. In particular, the chapter introduces and discusses in a little detail a variety of different numerical approaches to discretizing the equations in both the temporal and spatial dimensions. Discussing these in terms of their accuracy and numerical stability, as well as aspects of their efficiency on supercomputer architectures, it hopefully emerges why there is not a dominant strategy for designing a dynamical core.

In this paper we define the first Regional Atmosphere and Land (RAL) science configuration for kilometre-scale modelling using the Unified Model (UM) as the basis for the atmosphere and the Joint UK Land Environment Simulator (JULES) for the land. RAL1 defines the science configuration of the dynamics and physics schemes of the atmosphere and land. This configuration will provide a model baseline for any future weather or climate model developments to be described against, and it is the intention that from this point forward significant changes to the system will be documented in the literature. This reproduces the process used for global configurations of the UM, which was first documented as a science configuration in 2011. While it is our goal to have a single defined configuration of the model that performs effectively in all regions, this has not yet been possible. Currently we define two sub-releases, one for mid-latitudes (RAL1-M) and one for tropical regions (RAL1-T). The differences between RAL1-M and RAL1-T are documented, and where appropriate we define how the model configuration relates to the corresponding configuration of the global forecasting model.

Background: The EVOLVE (evaluating evidence, enhancing efficiencies) initiative aims to drive safer, higher-quality patient care through identifying and reducing low-value practices. Aims: To determine the Australian Rheumatology Association's (ARA) top five' list of low-value practices. Methods: A working group comprising 19 rheumatologists and three trainees compiled a preliminary list. Items were retained if there was strong evidence of low value and there was high or increasing clinical use and/or increasing cost. All ARA members (356 rheumatologists and 72 trainees) were invited to indicate their top five' list from a list of 12-items through SurveyMonkey in December 2015 (reminder February 2016). Results: A total of 179 rheumatologists (50.3%) and 19 trainees (26.4%) responded. The top five list (percentage of rheumatologists, including item in their top five list) was: Do not perform arthroscopy with lavage and/or debridement for symptomatic osteoarthritis of the knee nor partial meniscectomy for a degenerate meniscal tear (73.2%); Do not order anti-nuclear antibody (ANA) testing without symptoms and/or signs suggestive of a systemic rheumatic disease (56.4%); Do not undertake imaging for low back pain for patients without indications of an underlying serious condition (50.8%); Do not use ultrasound guidance to perform injections into the subacromial space as it provides no additional benefit in comparison to landmark-guided injection (50.3%) and Do not order anti-double-stranded DNA antibodies in ANA negative patients unless the clinical suspicion of systemic lupus erythematosus remains high (45.3%). Conclusions: This list is intended to increase awareness among rheumatologists, other clinicians and patients about commonly used low-value practices that should be questioned.

Habermas’ sense of a “cultural Public Sphere” is a notoriously complex term and, when applied to Early Modern cultures, needs careful definition. This essay both introduces the variety of methods by which we might approach playtexts with a view to their public – auditory – impact and contributes to a debate about an audience's understanding of Shakespeare's plays. By selecting two words and their spread of use in one play, Twelfth Night, we might appreciate the potential for meaningful ambiguity latent in how we hear the language of live performance. If we search for how certain terms (in this case, the cluster of semes derived from repetitions of “fancy” and “play”), we might find at times incompatible senses, yet we get near to appreciating the range of Early Modern dramatic language.

In this paper we define the first "Regional Atmosphere and Land" (RAL) science configuration for kilometre scale modelling using the UM and JULES. "RAL1" defines the science configuration of the dynamics and physics schemes of the atmosphere and land. This configuration will provide a model baseline for any future weather or climate model developments to be described against and it is the intention that from this point forward significant changes to the system will be documented in literature. This is reproducing the process used for global configurations of the UM which was first documented as a science configuration in 2011. While it is our goal to have a single defined configuration of the model that performs effectively in all regions, this has not yet been possible. Currently we define two sub-releases, one for mid-latitudes (RAL1-M) and one for tropical regions (RAL1-T). The differences between RAL1-M and RAL1-T are documented and where appropriate, we define how the model configuration relates to the corresponding configuration of the global forecasting model.

To meet the challenges posed by future generations of massively parallel supercomputers a reformulation of the dynamical core for the Met Office’s weather and climate model is presented. This new dynamical core uses explicit finite‐volume type discretisations for the transport of scalar fields coupled with an iterated‐implicit, mixed finite‐element discretisation for all other terms. The target model aims to maintain the accuracy, stability and mimetic properties of the existing Met Office model independent of the chosen mesh while improving the conservation properties of the model. This paper details that proposed formulation and, as a first step towards complete testing, demonstrates its performance for a number of test cases in (the context of) a Cartesian domain. The new model is shown to produce similar results to both the existing semi‐implicit semi‐Lagrangian model used at the Met Office and other models in the literature on a range of bubble tests and orographically forced flows in two and three dimensions.

The high-fired ceramics of Song China (960–1279) owe most of their glaze colours to iron oxides, generally in glass-solution, although occasionally in crystalline suspension. There is though, another metallic oxide that has been present in high-fired Chinese glazes since their first appearance in the early 16th C BCE through to modern times. This is titanium dioxide (TiO2, titania), a natural impurity in most rocks, clays and ashes and in the clays and glazes made from them. Titania is not a true glaze colourant but it can turn iron-blue glazes green by oxidising some Fe2+ ions to Fe3+ at full kiln temperatures. This rather obscure reaction has recently been studied scientifically and is now regarded as a key factor in the broader understanding of China’s high-fired ceramics, particularly those of the Song Dynasty. Titania’s influence on glaze colour has also proved important in understanding China’s ancient and extensive ash-glazed stoneware tradition, the development of Chinese white porcelain in the Sui Dynasty (581–618), the creation of Jingdezhen’s porcelain industry in the early 10th C CE, the manufacture of the finest Song imperial stoneware glazes, and the vast production of porcellanous celadon wares that developed in south-eastern China from the 13th to the 15th Cs.

Numerical weather, climate, or Earth system models involve the coupling of components. At a broad level, these components can be classified as the resolved fluid dynamics, unresolved fluid dynamical aspects (i.e., those represented by physical parameterizations such as subgrid-scale mixing), and nonfluid dynamical aspects such as radiation and microphysical processes. Typically, each component is developed, at least initially, independently. Once development is mature, the components are coupled to deliver a model of the required complexity. The implementation of the coupling can have a significant impact on the model. As the error associated with each component decreases, the errors introduced by the coupling will eventually dominate. Hence, any improvement in one of the components is unlikely to improve the performance of the overall system. The challenges associated with combining the components to create a coherent model are here termed physics–dynamics coupling. The issue goes beyond the coupling between the parameterizations and the resolved fluid dynamics. This paper highlights recent progress and some of the current challenges. It focuses on three objectives: to illustrate the phenomenology of the coupling problem with references to examples in the literature, to show how the problem can be analyzed, and to create awareness of the issue across the disciplines and specializations. The topics addressed are different ways of advancing full models in time, approaches to understanding the role of the coupling and evaluation of approaches, coupling ocean and atmosphere models, thermodynamic compatibility between model components, and emerging issues such as those that arise as model resolutions increase and/or models use variable resolutions.

A warm bias in tropical tropopause temperature is found in the Met Office Unified Model (MetUM), in common with most models from phase 5 of CMIP (CMIP5). Key dynamical, microphysical, and radiative processes influencing the tropical tropopause temperature and lower-stratospheric water vapor concentrations in climate models are investigated using the MetUM. A series of sensitivity experiments are run to separate the effects of vertical advection, ice optical and microphysical properties, convection, cirrus clouds, and atmospheric composition on simulated tropopause temperature and lower-stratospheric water vapor concentrations in the tropics. The numerical accuracy of the vertical advection, determined in the MetUM by the choice of interpolation and conservation schemes used, is found to be particularly important. Microphysical and radiative processes are found to influence stratospheric water vapor both through modifying the tropical tropopause temperature and through modifying upper-tropospheric water vapor concentrations, allowing more water vapor to be advected into the stratosphere. The representation of any of the processes discussed can act to significantly reduce biases in tropical tropopause temperature and stratospheric water vapor in a physical way, thereby improving climate simulations.

We present highlights from a large set of simulations of a hot Jupiter atmosphere, nominally based on HD 209458b, aimed at exploring both the evolution of the deep atmosphere, and the acceleration of the zonal flow or jet. We find the occurrence of a super-rotating equatorial jet is robust to changes in various parameters, and over long timescales, even in the absence of strong inner or bottom boundary drag. This jet is diminished in one simulation only, where we strongly force the deep atmosphere equator-to-pole temperature gradient over long timescales. Finally, although the eddy momentum fluxes in our atmosphere show similarities with the proposed mechanism for accelerating jets on tidally-locked planets, the picture appears more complex. We present tentative evidence for a jet driven by a combination of eddy momentum transport and mean flow., 26 pages, 22 Figures. Accepted for publication in Astronomy and Astrophysics

A method for imposing mass conservation in limited-area models (LAMs) with non-conservative semi-Lagrangian advection is proposed. The key feature of the scheme is to estimate the budget of the total mass through the lateral boundaries by splitting the original field into interior and exterior areas and to advect them individually. Idealized and real test cases show the reduction in error of the total mass, especially in the case when a monotonicity filter is applied.

Through a combination of analysis and synthesis of Laohudong Guan ware shards from Hangzhou City in southern China, some new hypotheses concerning Guan ware manufacture can be proposed. These suggest that the complex microstructures seen in Guan ware glazes, and which contribute significantly to their jade-like qualities, may owe much to layers of fine bubbles trapped during the glazing process. It is also proposed that the multi-layer glazing methods used at the Guan ware kilns at Hangzhou may have helped initially to disguise the relatively coarse and ferruginous clays used for Guan ware manufacture. Once established, the layered glazing technique was used for its own sake—eventually yielding wares that could comprise more glaze than clay. Raw materials and firing temperatures were also explored for this study, and these suggest the use of porcelain-stone/wood ash mixtures for glaze-making, with 20–30% calcareous wood ash being the usual amounts. The average heat-work for the glaze firing seems to have been equivalent to Orton Cone 7, giving a typical finishing temperature of ∼1215°C. A single biscuit firing and a single glaze firing seem likely for most Laohudong Guan wares. Studies of the losses that occur in the preparation of calcareous wood ashes suggest that very large quantities of botanic material must have been burned to provide ash for glaze-making at the Laohudong kiln. From the environmental perspective, a combination of thick glazes and heavy wood-ash usage would have placed great demands on local fuel supplies.

With the prospect of exascale computing, computational methods requiring only local data become especially attractive. Consequently, the typical domain decomposition of atmospheric models means horizontally-explicit vertically-implicit (HEVI) time-stepping schemes warrant further attention. In this analysis, Runge-Kutta implicit-explicit schemes from the literature are analysed for their stability and accuracy using a von Neumann stability analysis of two linear systems. Attention is paid to the numerical phase to indicate the behaviour of phase and group velocities. Where the analysis is tractable, analytically derived expressions are considered. For more complicated cases, amplification factors have been numerically generated and the associated amplitudes and phase diagnosed. Analysis of a system describing acoustic waves has necessitated attributing the three resultant eigenvalues to the three physical modes of the system. To do so, a series of algorithms has been devised to track the eigenvalues across the frequency space. The result enables analysis of whether the schemes exactly preserve the non-divergent mode; and whether there is evidence of spurious reversal in the direction of group velocities or asymmetry in the damping for the pair of acoustic modes. Frequency ranges that span next-generation high-resolution weather models to coarse-resolution climate models are considered; and a comparison is made of errors accumulated from multiple stability-constrained shorter time-steps from the HEVI scheme with a single integration from a fully implicit scheme over the same time interval. Two schemes, “Trap2(2,3,2)” and “UJ3(1,3,2)”, both already used in atmospheric models, are identified as offering consistently good stability and representation of phase across all the analyses. Furthermore, according to a simple measure of computational cost, “Trap2(2,3,2)” is the least expensive.

Recently, new test cases and associated measures have been proposed in the literature to evaluate the mixing and filament preservation properties of transport schemes on the sphere. In this Note, we evaluate the performance of SLICE and a semi-Lagrangian scheme with a new conservative correction using these tests and diagnostics. The results show that, based on these measures, both schemes considered here perform well and produce results comparable to some results in the literature. However, SLICE outperforms other schemes for some measures.

The equations governing atmospheric flow imply transfers of energy and potential enstrophy between scales. Accurate simulation of turbulent flow requires that numerical models, which have finite resolution and truncation errors, adequately capture these interscale transfers, particularly between resolved and unresolved scales. It is therefore important to understand how accurately these transfers are modelled in the presence of scale-selective dissipation or other forms of subgrid model. Here, the energy and enstrophy cascades in numerical models of two-dimensional turbulence are investigated using the barotropic vorticity equation. Energy and enstrophy transfers in spectral space due to truncated scales are calculated for a high-resolution reference solution and for several explicit and implicit subgrid models at coarser resolution. The reference solution shows that enstrophy and energy are removed from scales very close to the truncation scale and energy is transferred (backscattered) into the large scales. Some subgrid models are able to capture the removal of enstrophy from small scales, though none are scale-selective enough; however, none are able to capture accurately the energy backscatter. We propose a scheme that perturbs the vorticity field at each time step by the addition of a particular vorticity pattern derived by filtering the predicted vorticity field. Although originally conceived as a parametrization of energy backscatter, this scheme is best interpreted as an energy ‘fixer’ that attempts to repair the damage to the energy spectrum caused by numerical truncation error and an imperfect subgrid model. The proposed scheme improves the energy and enstrophy behaviour of the solution and, in most cases, slightly reduces the root mean square vorticity errors.

We describe Global Atmosphere 6.0 and Global Land 6.0 (GA6.0/GL6.0): the latest science configurations of the Met Office Unified Model and JULES (Joint UK Land Environment Simulator) land surface model developed for use across all timescales. Global Atmosphere 6.0 includes the ENDGame (Even Newer Dynamics for General atmospheric modelling of the environment) dynamical core, which significantly increases mid-latitude variability improving a known model bias. Alongside developments of the model's physical parametrisations, ENDGame also increases variability in the tropics, which leads to an improved representation of tropical cyclones and other tropical phenomena. Further developments of the atmospheric and land surface parametrisations improve other aspects of model performance, including the forecasting of surface weather phenomena. We also describe GA6.1/GL6.1, which includes a small number of long-standing differences from our main trunk configurations that we continue to require for operational global weather prediction. Since July 2014, GA6.1/GL6.1 has been used by the Met Office for operational global numerical weather prediction, whilst GA6.0/GL6.0 was implemented in its remaining global prediction systems over the following year.

The scientific understanding of the Earth's climate system, including the central question of how the climate system is likely to respond to human-induced perturbations, is comprehensively captured in GCMs and Earth System Models(ESM). Diagnosing the simulated climate response, and comparing responses across different models, is crucially dependent on transparent assumptions of how the GCM/ESM has been driven – especially because the implementation can involve subjective decisions and may differ between modelling groups performing the same experiment. This paper outlines the climate forcings and setup of the Met Office Hadley Centre ESM, HadGEM2-ES for the CMIP5 set of centennial experiments. We document the prescribed greenhouse gas concentrations, aerosol precursors, stratospheric and tropospheric ozone assumptions, as well as implementation of land-use change and natural forcings for the HadGEM2-ES historical and future experiments following the Representative Concentration Pathways. In addition, we provide details of how HadGEM2-ES ensemble members were initialised from the control run and how the palaeoclimate and AMIP experiments, as well as the "emission-driven" RCP experiments were performed.

The semi-Lagrangian numerical method, in conjunction with semi-implicit time integration, provides numerical weather prediction models with numerical stability for large time steps, accurate modes of interest, and good representation of hydrostatic and geostrophic balance. Drawing on the legacy of dynamical cores at the Met Office, the use of the semi-implicit semi-Lagrangian method in an operational numerical weather prediction context is surveyed, together with details of the solution approach and associated issues and challenges. The numerical properties and performance of the current operational version of the Met Office’s numerical model are then investigated in a simplified setting along with the impact of different modelling choices.

A wide family of exact closed-form axisymmetric solutions to the deep- and shallow-atmosphere Euler equations is derived. These solutions are not only valid in general curvilinear geometry, but also in beta-plane and beta–gamma-plane geometries. A further generalisation of the generalised thermal wind equation is also derived. The enhanced generality of the exact solutions developed herein provides more flexibility in the specification of initial conditions for numerical model validation. This permits the construction not only of more challenging, balanced, shallow- and deep-atmosphere solutions than has hitherto been possible, but also of more elaborate tests of the baroclinic wave type. Copyright © 2012 British Crown copyright, the Met Office. Published by John Wiley & Sons Ltd.

Accurate coupling between the resolved-scale dynamics and the parametrised physics is essential for accurate modelling of the atmosphere. Previous emphasis has been on the temporal aspects of this so-called physics–dynamics coupling problem, with little attention on the spatial aspects. When designing a model for numerical weather prediction there is a choice for how to vertically arrange the predicted variables, namely the Lorenz and Charney–Phillips grids, and there is ongoing debate as to which is the optimal. The Charney–Phillips grid is considered good for capturing the potential vorticity dynamics and wave propagation, whereas the Lorenz grid is more suitable for conservation. However the Lorenz grid supports a computational mode. It is argued here that the Lorenz grid is preferred for modelling the stably stratified boundary layer. This presents the question: which grid will produce more accurate results when coupling the large-scale dynamics to the stably stratified planetary boundary layer? The question is addressed by examining the ability of both the Lorenz and Charney–Phillips grids to capture the steady state of a set of equations that simultaneously represents both large-scale dynamics and the planetary boundary layer. The results show that the Charney–Phillips grid is able to capture accurately the steady boundary-layer solution provided the Richardson number is calculated without vertically averaging the shear. Averaging the shear suppresses the negative feedback of the shear on the diffusion coefficient; the positive feedback, via the vertical gradient of potential temperature, then leads to the formation of unrealistic step-like features. Copyright © 2012 Royal Meteorological Society

In order to investigate questions concerning changes in the atmosphere and other components of the Earth system, it is desirable to have a seamless modelling system that operates across a wide range of time-scales and horizontal resolutions. The development of a low-resolution configuration of the model would greatly assist in addressing these scientific questions whose long time-scales or complexity are computationally demanding—a cost that cannot be sustained by higher resolutions. However, in order to be confident that results remain robust to changes in resolution, it is essential that such models include the same underlying fundamental processes as those at higher resolution. Some resolution-dependent biases are found to grow (notably when horizontal resolution decreases below ∼150 km) as a result of the lack of transient eddy kinetic energy (TEKE). The advection scheme used by many of the current general circulation models follows the semi-Lagrangian (SL) dynamics approach. Because of the need for interpolation to the departure point, the scheme is highly diffusive when low-order interpolation schemes are used. We analyse how the impact of the high diffusivity of SL schemes leads to a lack of TEKE, which inhibits the development of mid-latitude variability phenomena such as synoptic cyclones or blocking events. Conversely, some examples where the performance of the low resolution is acceptable are provided. We investigate two different traceable solutions to partially offset the misrepresentation of dynamical features in the low-resolution version: a change of the interpolation scheme from quasi-cubic to quintic interpolation; and vorticity confinement: a parametrization designed to preserve vorticity features in dissipative numerical schemes. Both solutions are found to increase TEKE and improve many of the mid-latitude metrics considered. Copyright © 2012 British Crown copyright, the Met Office. Published by John Wiley & Sons Ltd.

The Ding kilns were some of the most famous early kilns of medieval China, producing huge quantities of white and cream-white porcelains of outstanding technical and aesthetic quality. Since 1949 they have been excavated three times, in 1965, in 1987, and in 2009 respectively. In this latest study 69 white porcelain sherds from assured contexts and from the 2009 excavations were analyzed using laser ablation techniques (ICP-AES). The samples date from Five Dynasties, Northern Song and Jin Dynasties respectively (early 10 th to early 13 th C CE). The results show that Ding wares of different times show different characteristics that can be demonstrated through chemical composition. During the early phase of production the Ding ware bodies consisted largely of high firing kaolinitic clays with predominantly calcareous materials as fluxes. After the early Northern Song Dynasty, some calcareous material was replaced by a more potassic material. The compositions of the glazes show a parallel evolution to the bodies. However, because the glazes are very low in titania it seems unlikely that the main clay ingredients of the bodies could have been used in the glaze recipes. For much of the kiln site’s history the glazes appear to have been made mainly from the same siliceous flux-rich materials that had been blended with the main body-clays used to make the Ding ware porcelains, plus some extra calcareous material. The P 2 O 5 contents of the glazes suggest that wood ash may have been one source of CaO in the glaze recipes.

Taking the spherical geopotential approximation as a starting point, previous work has revealed a quartet of dynamically consistent models of the global atmosphere according to whether approximations of shallow and quasi-hydrostatic type are or are not made. The generalization of this quartet of consistent models is sought within the framework of geopotential surfaces that are zonally symmetric but not assumed to be spherical. The distinction between approximations of shallow and quasi-hydrostatic type is more subtle than in the spherical case: consistent quasi-hydrostatic approximation requires the simultaneous omission of two metric terms that vanish identically in the spherical case (and indeed whenever the vertical metric factor is independent of the meridional coordinate). These two metric terms are not eliminated by the formal process of metric factor approximation by which consistent models of shallow type may be generated. Consistently approximated, hydrostatic, shallow forms are obtained by applying quasi-hydrostatic and shallow approximations successively, and are comparable with the well-known spherical geopotential forms as regards the number and nature of the terms present. The formulation of shallow-water models in non-spherical geopotential coordinates is considered in conclusion. Copyright © 2011 British Crown copyright, the Met Office. Published by John Wiley & Sons Ltd.

Numerical models of the atmosphere cannot resolve all relevant scales; the effects of unresolved scales on resolved scales must be represented by a subgrid model or parametrization. When the unresolved scales are similar in character to the resolved scales (as in three-dimensional or layerwise two-dimensional turbulence) the problem is essentially one of large eddy simulation. In this situation, one approach to subgrid modelling is implicit large eddy simulation (ILES), where the truncation errors of the numerical model attempt to act as the subgrid model. ILES has been shown to have some success for three-dimensional turbulence, but the validity of the approach has not previously been examined for two-dimensional or layerwise two-dimensional flow, which is the regime relevant to weather and climate modelling. Two-dimensional turbulence differs qualitatively from threedimensional turbulence in several ways, most notably in having upscale energy and downscale enstrophy transfers. The question is of practical importance since many atmospheric models in effect use the ILES approach, for example through the use of a semi-Lagrangian advection scheme. In this paper a number of candidate numerical schemes are tested to determine whether their truncation errors can approximate the subgrid terms of the barotropic vorticity equation. Results show that some schemes can implicitly model the effects of the subgrid term associated with the stretching and thinning of vorticity filaments to unresolvable scales; the subgrid term is then diffusive and is associated with the downscale enstrophy transfer. Conservation of vorticity, by using a flux form scheme rather than advective form for advection of vorticity, was found to improve performance of a candidate ILES scheme. Some effects of the subgrid terms could not be captured by any of the schemes tested, whether using an implicit or a simple explicit subgrid model: none of the schemes tested is able to capture the upscale transfer of energy from unresolved to resolved scales. Copyright c � 2011 Royal Meteorological Society and

The microstructures of porcelain and stoneware bodies from north and south China, spanning the period from the Tang to the Ming dynasty (7th–17th centuries ad), were examined in polished sections in a scanning electron microscope (SEM) after etching the sections with hydrofluoric acid (HF). Mullite, present as fine, mainly elongated crystals, is the dominant crystalline phase observed. The bulk chemical compositions of the bodies are determined by energy-dispersive spectrometry in the SEM, and the relative amounts of mullite and quartz present in the different ceramics are estimated from X-ray diffraction measurements. Mullite formed from areas of kaolinitic clay, mica particles and feldspar particles is distinguished through a combination of the arrangement of the mullite crystals, and the associated SiO2/Al2O3 wt% concentration ratios. It is shown that very different microstructures are observed in ceramic bodies produced using kaolinitic clay from north China (Ding porcelain and Jun stoneware), porcelain stone from south China (qingbai and underglaze blue porcelain and Longquan stoneware), and stoneware clays from south China (Yue and Guan stonewares). Therefore, SEM examination of HF-etched, polished sections of the bodies of high-refractory ceramics has considerable potential for investigating the raw materials used in their production.