Publications


The Gulf Stream influence on wintertime North Atlantic jet variability

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 143 (2017) 173-183

CH O'Reilly, S Minobe, A Kuwano-Yoshida, T Woollings


Seasonal and decadal forecasts of Atlantic Sea surface temperatures using a linear inverse model

CLIMATE DYNAMICS 49 (2017) 1833-1845

B Huddart, A Subramanian, L Zanna, T Palmer


Remote control of North Atlantic Oscillation predictability via the stratosphere

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 143 (2017) 706-719

F Hansen, RJ Greatbatch, G Gollan, T Jung, A Weisheimer


Ice-shelf damming in the glacial Arctic Ocean: dynamical regimes of a basin-covering kilometre-thick ice shelf

CRYOSPHERE 11 (2017) 1745-1765

J Nilsson, M Jakobsson, C Borstad, N Kirchner, G Bjork, RT Pierrehumbert, C Stranne


Assessing mid-latitude dynamics in extreme event attribution systems

CLIMATE DYNAMICS 48 (2017) 3889-3901

D Mitchell, P Davini, B Harvey, N Massey, K Haustein, T Woollings, R Jones, F Otto, B Guillod, S Sparrow, D Wallom, M Allen


Climate SPHINX: evaluating the impact of resolution and stochastic physics parameterisations in the EC-Earth global climate model

GEOSCIENTIFIC MODEL DEVELOPMENT 10 (2017) 1383-1402

P Davini, J von Hardenberg, S Corti, HM Christensen, S Juricke, A Subramanian, PAG Watson, A Weisheimer, TN Palmer


Variability in seasonal forecast skill of Northern Hemisphere winters over the 20th century

Geophysical Research Letters American Geophysical Union (AGU) (2017)

C O'Reilly, MacLeod, A Weisheimer, T Palmer, T Woollings


A deformation-based parametrization of ocean mesoscale eddy reynolds stresses

Ocean Modelling 112 (2017) 99-111

JA Anstey, L Zanna

© 2017 The Authors Ocean mesoscale eddies strongly affect the strength and variability of large-scale ocean jets such as the Gulf Stream and Kuroshio Extension. Their spatial scales are too small to be fully resolved in many current climate models and hence their effects on the large-scale circulation need to be parametrized. Here we propose a parametrization of mesoscale eddy momentum fluxes based on large-scale flow deformation. The parametrization is argued to be suitable for use in eddy-permitting ocean general circulation models, and is motivated by an analogy between turbulence in Newtonian fluids (such as water) and laminar flow in non-Newtonian fluids. A primitive-equations model in an idealised double-gyre configuration at eddy-resolving horizontal resolution is used to diagnose the relationship between the proposed closure and the eddy fluxes resolved by the model. Favourable correlations suggest the closure could provide an appropriate deterministic parametrization of mesoscale eddies. The relationship between the closure and different representations of the Reynolds stress tensor is also described. The parametrized forcing possesses the key quasi-geostrophic turbulence properties of energy conservation and enstrophy dissipation, and allows for upgradient fluxes leading to the sharpening of vorticity gradients. The implementation of the closure for eddy-permitting ocean models requires only velocity derivatives and a single parameter that scales with model resolution.


The primacy of doubt: Evolution of numerical weather prediction from determinism to probability

JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS 9 (2017) 730-734

T Palmer


Global meteorological influences on the record UK rainfall of winter 2013-14

ENVIRONMENTAL RESEARCH LETTERS 12 (2017) ARTN 074001

JR Knight, A Maidens, PAG Watson, M Andrews, S Belcher, G Brunet, D Fereday, CK Folland, AA Scaife, J Slingo


On the use of scale-dependent precision in Earth System modelling

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 143 (2017) 897-908

T Thornes, P Duben, T Palmer


Single Precision in Weather Forecasting Models: An Evaluation with the IFS

MONTHLY WEATHER REVIEW 145 (2017) 495-502

F Vana, P Duben, S Lang, T Palmer, M Leutbecher, D Salmond, G Carver


The statistical nature of turbulent barotropic ocean jets

OCEAN MODELLING 113 (2017) 34-49

TW David, DP Marshall, L Zanna


Scale-aware deterministic and stochastic parametrizations of eddy-mean flow interaction

Ocean Modelling 111 (2017) 66-80

L Zanna, PGL Porta Mana, J Anstey, T David, T Bolton

© 2017 The Authors The role of mesoscale eddies is crucial for the ocean circulation and its energy budget. The sub-grid scale eddy variability needs to be parametrized in ocean models, even at so-called eddy permitting resolutions. Porta Mana and Zanna (2014) propose an eddy parametrization based on a non-Newtonian stress which depends on the partially resolved scales and their variability. In the present study, we test two versions of the parametrization, one deterministic and one stochastic, at coarse and eddy-permitting resolutions in a double gyre quasi-geostrophic model. The parametrization leads to drastic improvements in the mean state and variability of the ocean state, namely in the jet rectification and the kinetic-energy spectra as a function of wavenumber and frequency for eddy permitting models. The parametrization also appears to have a stabilizing effect on the model, especially the stochastic version. The parametrization possesses attractive features for implementation in global models: very little computational cost, it is flow aware and uses the properties of the underlying flow. The deterministic coefficient is scale-aware, while the stochastic parameter is scale- and flow-aware with dependence on resolution, stratification and wind forcing.


Drivers of uncertainty in simulated ocean circulation and heat uptake

Geophysical Research Letters 44 (2017) 1402-1413

MB Huber, L Zanna

©2017. The Authors. The impact of uncertainties in air-sea fluxes and ocean model parameters on the ocean circulation and ocean heat uptake (OHU) is assessed in a novel modeling framework. We use an ocean-only model forced with the simulated sea surface fields of the CMIP5 climate models. The simulations are performed using control and 1% CO 2 warming scenarios. The ocean-only ensemble adequately reproduces the mean Atlantic Meridional Overturning Circulation (AMOC) and the zonally integrated OHU. The ensemble spread in AMOC strength, its weakening, and Atlantic OHU due to different air-sea fluxes is twice as large as the uncertainty range related to vertical and mesocale eddy diffusivities. The sensitivity of OHU to uncertainties in air-sea fluxes and model parameters differs vastly across basins, with the Southern Ocean exhibiting strong sensitivity to air-sea fluxes and model parameters. This study clearly demonstrates that model biases in air-sea fluxes are one of the key sources of uncertainty in climate simulations.


A note on ‘Toward a stochastic parameterization of ocean mesoscale eddies’

Ocean Modelling 113 (2017) 30-33

I Grooms, L Zanna

© 2017 Porta Mana and Zanna (2014) recently proposed a subgrid-scale parameterization for eddy-permitting quasigeostrophic models. In this model the large-scale fluid is represented as a non-Newtonian viscoelastic medium, with a subgrid-stress closure that involves the Lagrangian derivative of large-scale quantities. This note derives this parameterization, including the nondimensional proportionality coefficient, using only two statistical assumptions: that the subgrid-scale term is locally homogeneous and decorrelates rapidly in space. The parameterization is then verified by comparing against eddy-resolving quasigeostrophic simulations, independently reproducing the results of Porta Mana and Zanna in a simpler model.


Stochastic Subgrid-Scale Ocean Mixing: Impacts on Low-Frequency Variability

JOURNAL OF CLIMATE 30 (2017) 4997-5019

S Juricke, TN Palmer, L Zanna


Observational evidence against strongly stabilizing tropical cloud feedbacks

GEOPHYSICAL RESEARCH LETTERS 44 (2017) 1503-1510

IN Williams, RT Pierrehumbert


Reconstructing Climate from Glaciers

Annual Review of Earth and Planetary Sciences 45 (2017)

AN Mackintosh, BM Anderson, RT Pierrehumbert


Impact of stochastic physics on tropical precipitation in the coupled ECMWF model

QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY 143 (2017) 852-865

A Subramanian, A Weisheimer, T Palmer, F Vitart, P Bechtold

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