A new dynamical core for the Met Office's global and regional modelling of the atmosphere

Davies, Terry; Cullen, M. J. P.; Malcolm, Andrew J.; Mawson, M. H.; Staniforth, Andrew; White, A. A.; Wood, Nigel

doi:10.1256/qj.04.101

Cited by 958 publications

(849 citation statements)

References 60 publications

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“…HadGEM3-GA6.0 was the closest available model configuration to HadGEM3-GA3.0 at the time the sensitivity experiment was conducted. Differences between GA6.0 and GA3.0 include small adaptations to the semi-implicit semiLagrangian dynamical core from "New Dynamics" (Davies et al, 2005) to ENDGame (Even Newer Dynamics for General atmospheric modelling of the environment; Wood et al, 2014) and the new "5A" subgrid orographic drag parameterisation (Vosper, 2015;Wells, 2015) replacing the previous "4A" scheme (Webster et al, 2003).…”

Section: Model Ensemblementioning

confidence: 99%

Mean and extreme precipitation over European river basins better simulated in a 25 km AGCM

Schiemann

Vidale

Shaffrey

et al. 2018

Hydrol. Earth Syst. Sci.

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Abstract. Limited spatial resolution is one of the factors that may hamper applications of global climate models (GCMs), in particular over Europe with its complex coastline and orography. In this study, the representation of European mean and extreme precipitation is evaluated in simulations with an atmospheric GCM (AGCM) at different resolutions between about 135 and 25 km grid spacing in the mid-latitudes. The continent-wide root-mean-square error in mean precipitation in the 25 km model is about 25 % smaller than in the 135 km model in winter. Clear improvements are also seen in autumn and spring, whereas the model's sensitivity to resolution is very small in summer. Extreme precipitation is evaluated by estimating generalised extreme value distributions (GEVs) of daily precipitation aggregated over river basins whose surface area is greater than 50 000 km 2 . GEV location and scale parameters are measures of the typical magnitude and of the interannual variability of extremes, respectively. Median model biases in both these parameters are around 10 % in summer and around 20 % in the other seasons. For some river basins, however, these biases can be much larger and take values between 50 % and 100 %. Extreme precipitation is better simulated in the 25 km model, especially during autumn when the median GEV parameter biases are more than halved, and in the North European Plains, from the Loire in the west to the Vistula in the east. A sensitivity experiment is conducted showing that these resolution sensitivities in both mean and extreme precipitation are in many areas primarily due to the increase in resolution of the model orography. The findings of this study illustrate the improved capability of a global high-resolution model in simulating European mean and extreme precipitation.

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Section: Model Ensemblementioning

confidence: 99%

Mean and extreme precipitation over European river basins better simulated in a 25 km AGCM

Schiemann

Vidale

Shaffrey

et al. 2018

Hydrol. Earth Syst. Sci.

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“…The advective, vector form is used for the momentum equation and, departing from [1], the Eulerian flux form is employed for the continuity equation, in order to ensure mass conservation, along the lines of the approach pursued in [7][8][9][10]:…”

Section: Governing Equationsmentioning

confidence: 99%

“…Furthermore, in order to avoid the solution of a nonlinear system at each timestep, the dependency on h in ∇ · (hu) is frozen in time to the latest computed value [7][8][9][10].…”

Section: A Tr-bdf2 Time Integration Approach For the Shallow Water Eqmentioning

confidence: 99%

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A mass conservative TR-BDF2 semi-implicit semi-Lagrangian DG discretization of the shallow water equations on general structured meshes of quadrilaterals

Tumolo

2016

Communications in Applied and Industrial Mathematics

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As an extension of a previous work considering a fully advective formulation on Cartesian meshes, a mass conservative discretization approach is presented here for the shallow water equations, based on discontinuous finite elements on general structured meshes of quadrilaterals. A semi-implicit time integration is performed by employing the TR-BDF2 scheme and is combined with the semi-Lagrangian technique for the momentum equation only. Indeed, in order to simplify the derivation of the discrete linear Helmoltz equation to be solved at each time-step, a non-conservative formulation of the momentum equation is employed. The Eulerian flux form is considered instead for the continuity equation in order to ensure mass conservation. Numerical results show that on distorted meshes and for relatively high polynomial degrees, the proposed numerical method fully conserves mass and presents a higher level of accuracy than a standard off-centered Crank Nicolson approach. This is achieved without any significant imprinting of the mesh distortion on the solution.

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“…One method of reducing the cost of a local estimate is to truncate the calculation to a local simulation at a high resolution forced by boundary conditions given by a low resolution global simulation. For estimating the response to a forcing applied over a short time this regional approach seems effective, (see for example the UK Met office numerical weather prediction model Davies et al, 2005); however, it remains to be seen if it can be extended to the long time climate response. The hypothesis explored in this paper is that a statistical approximation based upon the fluctuation-dissipation theorem (FDT), using only data on the unforced system, will have some skill in predicting the response to a forcing.…”

Section: Introductionmentioning

confidence: 99%

Estimation of the local response to a forcing in a high dimensional system using the fluctuation-dissipation theorem

Cooper

Esler

Haynes

2013

Nonlin. Processes Geophys.

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The fluctuation-dissipation theorem (FDT) has been proposed as a method of calculating the response of the earth's atmosphere to a forcing. For this problem the high dimensionality of the relevant data sets makes truncation necessary. Here we propose a method of truncation based upon the assumption that the response to a localised forcing is spatially localised, as an alternative to the standard method of choosing a number of the leading empirical orthogonal functions. For systems where this assumption holds, the response to any sufficiently small non-localised forcing may be estimated using a set of truncations that are chosen algorithmically. We test our algorithm using 36 and 72 variable versions of a stochastic Lorenz 95 system of ordinary differential equations. We find that, for long integrations, the bias in the response estimated by the FDT is reduced from ~75% of the true response to ~30%

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A new dynamical core for the Met Office's global and regional modelling of the atmosphere

Cited by 958 publications

References 60 publications

Mean and extreme precipitation over European river basins better simulated in a 25 km AGCM

Mean and extreme precipitation over European river basins better simulated in a 25 km AGCM

A mass conservative TR-BDF2 semi-implicit semi-Lagrangian DG discretization of the shallow water equations on general structured meshes of quadrilaterals

Estimation of the local response to a forcing in a high dimensional system using the fluctuation-dissipation theorem

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