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© Crown copyright Met Office Implementation of a new dynamical core in the Met Office Unified Model Andy Brown, Director of Science
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© Crown copyright Met Office Implementation of a new dynamical core in the Met Office Unified Model Andy Brown, Director of Science.

Dec 13, 2015

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Crown copyright Met Office Implementation of a new dynamical core in the Met Office Unified Model Andy Brown, Director of Science Slide 2 Met Office science strategy: Unified science and modelling for unified prediction Slide 3 Crown copyright Met Office DePreSys TIGGE ensemble GloSea4 MOGREPS-R ensemble Coupled atmos/ocean Earth System Timescale 36hrs48hrs5 days 15 days 6 months 10 years 30 years >100 years 1.5km 4km 12km 24km 40km 80km 150km 300km Complexity UKV UK4 NAE Global HadCM3 HadGEM1 HadGEM2 Global atmosphere-only Regional atmosphere-only HadGEM3-RA regional HadGEM3 Atmospheric grid length Slide 4 Crown copyright Met Office A new dynamical core: ENDGame Atmos Physics 1 Advection Atmos Physics 2 Helmholtz Solver x2 Evolution of existing dynamics Same equation set & variables Same horizontal staggering (Arakawa C-grid) Same vertical staggering (Charney-Phillips) Iterative Semi-implicit semi-Lagrangian Simpler solver Less damping ( = 0.55) Fully 3D advection for Reformulated continuity equation More scalable More stable More accurate Slide 5 A possible timeline for a major model upgrade........ Quality Time (years) Operational Development Model Slide 6 Crown copyright Met Office Model changes alongside ENDGame Package of physics changes ENDGame+physics= GA6.0 (climate) GA6.1 (weather) GA6.0 and 6.1 extremely similar (more seamless than ever) For global NWP Model N512 (25km) N768 (17km) 4D-Var inner loop N216 (60km) N320 (40km) Satellite package Slide 7 ENDGame results Slide 8 Crown copyright Met Office Eddy Kinetic Energy T+72hr EKE from 10 x ECMWF cases Paul Earnshaw 9.0 7.0 N96N216N512N768 Slide 9 Crown copyright Met Office Extra-tropical circulation Equivalent plots from PS32-based trials See poster by David Walters July 2012 Slide 10 Crown copyright Met Office Tropical circulation Significant increases in variability Equatorial precip frequency/wavenumber spectrum from 20yr climate runs: Prince Xavier GA4.0GA6.0TRMM obs Slide 11 Crown copyright Met Office Tropical circulation Major improvements in Tropical Cyclone forecasts Impact of science upgrade N512 GA6.1 vs N512 GA3.1 Impact of science + resoln N768 GA6.1 vs N512 GA3.1 Mean abs. PMSL error reduction3.0 hPa3.6 hPa Central pressure reduction7.1 hPa11.1 hPa Mean abs. |v| error reductions6.7 kt9.0 kt Mean max. |v| increase8.9 kt13.4 kt 850hPa vorticity increase79%155% Track error reduction7.3% 8.6%* Track skill score increase3.8%4.5% Julian Heming, Keith Williams * Biggest reduction in TC track error in a single UM upgrade for 20 years! Average impacts from PS32-based trials: Slide 12 Crown copyright Met Office Hermite Cubic Control minus ERA-InterimHermite minus ERA-Interim Vertical advection of tropopause by small amplitude oscillations Cubic Lagrange = 3 rd order upwind scheme (cf. ND = 2 nd order centred) opposite phases of oscillation do not cancel: [z + dt*w - dt*w] (z) biased increments Remedy: Cubic Hermite enforce continuity of interpolation gradient Bias now close to that of New Dynamics Slide 13 Crown copyright Met Office New global versus 12km regional model Surface weather impacts (Temperature, cloud cover, cloud base, ppn, visibility) New global versus old global Significant improvement in near-surface weather measures Global outperforms 12km Limited Area Model now retired Global significantly behind 1.5km model for UK Slide 14 Crown copyright Met Office N. Atlantic SST bias in GloSea hindcasts GA3 (coupled) GC2 Ruth Comer Slide 15 Crown copyright Met Office Outgoing SW radiation New New minus Old Old minus climatology New minus climatology Dan Copsey Slide 16 ENSO Crown copyright Met Office Slide 17 Kilometre-scale modelling Closer to a centred semi-implicit approach Impact in UKV Lee Wave test: New Dynamics ENDGame Simon Vosper Slide 18 Crown copyright Met Office DePreSys TIGGE ensemble GloSea4 MOGREPS-R ensemble Coupled atmos/ocean Earth System Timescale 36hrs48hrs5 days 15 days 6 months 10 years 30 years >100 years 1.5km 4km 12km 24km 40km 80km 150km 300km Complexity UKV UK4 NAE Global HadCM3 HadGEM1 HadGEM2 Global atmosphere-only Regional atmosphere-only HadGEM3-RA regional HadGEM3 Atmospheric grid length Dynamics matters! Extremely significant model upgrade achieved in seamless framework Slide 19 Crown copyright Met Office Questions? Slide 20 Crown copyright Met Office Physics changes Significant physics differences between GA3.1 and GA6.1: Total of 66 tickets (including ENDGame) in GA4, GA5 and GA6 Slide 21 Crown copyright Met Office ENDGame in a nutshell Example of scalability vs New Dynamics ENDGame required for 17km in PS34 N768 GA6.1 on 96 nodes currently runs in 40 mins Allows further resolution upgrades over next 10 years Andy Malcolm, Paul Selwood

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