1. NCAS Unified Model Introduction Part 1a: Overview of the UM system University of Reading, 3-5 December 2014

2. The Unified Model The UM is a numerical modelling system, developed by the UK Met Office, and used for operational weather forecasting and climate prediction. It is licensed to the UK academic community for research. There is also the Joint Weather and Climate Research Programme (JWCRP), a strategic partnership between NERC and the Met Office for model development. 2 It is used by forecast centres and climate agencies around the world.

3. Seamless modelling The same core model is used across spatial and temporal scales: – Weather to climate timescales – Global and regional models – High to low resolution (horizontal and vertical) – Various model heights It can be used in atmosphere only mode, or coupled to: – UM ocean (vn6.6.3 or earlier only e.g. HadGEM2) – NEMO and CICE (ocean and sea-ice) via OASIS coupler – UKCA (chemistry and aerosols) – JULES (land-surface) It can also be used to perform idealised studies, e.g: – Single column model (SCM) – Aquaplanet 3

4. 4 Modified from a Met Office diagram. GloSea4 TIGGE 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 MOGREPS-R ensemble Global DePreSys PRECIS HadCM3 HadGEM1 HadGEM2 – ES Under Development Production system Retired Global atmosphere-only Regional atmosphere-only HadGEM3-RA regional UKESM1-Hi Atmospheric grid length GloSea5 Euro4 UKCM DePreSys HadGEM3-GC2 Global 4

5. Global & regional NWP system Global 17km 70 levels (N768L70) EURO 4km 70 levels UKV 1.5km 70 levels [Retired NAE 12km 70 levels] 5 © Crown copyright Met Office Parallel suite 34

6. NWP at the Met Office 6 © Crown copyright Met Office The UM is just one part of a larger forecast system. An example workflow: Academic users can access this data

7. Global models 7 Fixed resolutions: Common scientific configurations used across scales (weather, seasonal and climate): o GA = Global Atmosphere (UM) o GL = Global Land (JULES) o GO = Global Ocean (NEMO) o GSI = Global Sea Ice (CICE) o GC = Global Coupled (all of the above coupled together) These are ongoing developments with fixed releases. N96N144N216N320N512N768 (192 x 145)(288 x 217)(432 x 325) (640 x 481)(1024 x 769) (1536 x 1152) ~135 km~90 km~60 km~40 km~25 km~17 km 1.875° x 1.25°1.25° x 0.83°0.83° x 0.56° 0.56° x 0.375°0.35° x 0.234°0.234° x 0.16° (at mid-latitudes)

8. Vertical resolutions 8 © Crown copyright Met Office Standard resolutions Defined by model levels and height Example: L85 with top at 85 km

9. NWP v Climate models NWPClimate Run length5 day operational forecast, 15 day ensemble forecast Months (seasonal) Years, decades, centuries+ Global resolutionTesting: N320 (40 km) with 15 min ts Operational: N768 (17 km) with 7.5 min ts Low resolution: N96 (135 km) with 20 min ts High resolution: N512 (25 km) with 15 min ts CalendarGregorianSeasonal: Gregorian Other: 360 day DynamicsNon-bit reproducibleBit-reproducible AerosolsClimatological concentrations specified. Interactive schemes with emissions specified (not seasonal). 9 Based on information from Dan Copsey

10. HadGEM2(-ES) HadGEM2-ES Full Earth system model Development completed in 2009 Used for IPCC AR5 (CMIP5) N96 – 1° ocean 10 Aerosols and chemistry (UKCA) Ocean biogeochemistry Interactive vegetation (TRIFFID) Human emissions Physical climate Other versions available: -A (atmosphere only) -AO (coupled atmosphere-ocean) -CC (carbon-cycle) Earth system minus UKCA

11. HadGEM3(-AO) (Modified from a Met Office diagram.) 11 Under continuous development. There are versions with: different code releases different scientific configurations Multiple resolutions: N96 – ORCA0.25 N216 – ORCA0.25 N512 – ORCA0.25 / ORCA12 (experimental) Can run atmosphere-only UM atmosphere (GA) CICE sea ice (GSI)NEMO ocean model (GO) OASIS3 coupler JULES land surface (GL)

12. Other modelling systems MOGREPS: ensemble forecast – Based on Parallel Suites GloSea: seasonal prediction – Based on HadGEM3 coupled model with NEMO-CICE DePreSys: decadal prediction – Based on HadCM3 (due to be upgraded to HadGEM3) 12

13. Terminology Model version: defines the code base used. Model configuration: defines the science options, eg GA6.0, GO5.0. Modelling system: application with specific configuration (eg HadGEM3-GC2, GloSea5). Parallel suite: version of operational forecast system Job: particular instance defined and run by user Experiment: grouping of jobs in UMUI 13

14. Major UM developments 14 Old dynamics New dynamics FCMNEMO & CICE ENDGameRoseShared repositories UM 4.5UM 5.2UM 6.1UM 6.6UM 7.1UM 8.5UM 9.0(UM 10.0) 19982001200520072008201320142015 Climate models HadCM3HadGEM1 HadGEM2HadGEM3 NWP models PS12PS19PS20PS34(PS35) Dynamical coreInfrastructureOcean model …

15. Atmosphere model Dynamical core Physics parameterisations Diagnostics (STASH) [JULES and/or UKCA] UM software 15 UMUI Database of user jobs Graphical job editor FCM Code manager Compilation and build system Reconfiguration Prepares initial model state Input file tools Prepare ancillary data Output file tools Data processing Analysis and visualisation PUMA HPC Local / Jasmin OASIS Ocean model

16. NCAS supported machines 16 HPC user ssh to all Polaris UM submission RDF File systems: /home and /work MASS MONSooN File systems: /home, /projects and /nerc Lander Local Code repositories Web server (Trac) User /home space PUMA HPC Wales Jasmin