Part 1a: Overview of the UM system University of Reading, 18-20 March 2015

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. It is used by forecast centres and climate agencies around the world.

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

© Crown copyright Met Office

Global & regional NWP system Parallel suite 35 Global 17km 70 levels (N768L70) EURO 4km 70 levels UKV 1.5km 70 levels [Retired NAE 12km 70 levels] © Crown copyright Met Office

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

Global models Fixed resolutions: (at mid-latitudes) Fixed resolutions: N96 N144 N216 N320 N512 N768 (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° Common scientific configurations used across scales (weather, seasonal and climate): GA = Global Atmosphere (UM) GL = Global Land (JULES) GO = Global Ocean (NEMO) GSI = Global Sea Ice (CICE) GC = Global Coupled (all of the above coupled together) These are ongoing developments with fixed releases.

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

NWP v Climate models NWP Climate Run length 5 day operational forecast, 15 day ensemble forecast Months (seasonal) Years, decades, centuries+ Global resolution Testing: 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 Calendar Gregorian Seasonal: Gregorian Other: 360 day Dynamics Non-bit reproducible Bit-reproducible Aerosols Climatological concentrations specified. Interactive schemes with emissions specified (not seasonal). Based on information from Dan Copsey

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

HadGEM3(-AO) Under continuous development. There are versions with: UM atmosphere (GA) CICE sea ice (GSI) NEMO ocean model (GO) OASIS3 coupler JULES land surface (GL) 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 (Modified from a Met Office diagram.)

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)

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

Major UM developments Old dynamics New dynamics FCM NEMO & CICE ENDGame Rose Shared repositories UM 4.5 UM 5.2 UM 6.1 UM 6.6 UM 7.1 UM 8.5 UM 9.0 UM 10.0 1998 2001 2005 2007 2008 2013 2014 2015 Climate models HadCM3 HadGEM1 HadGEM2 HadGEM3 NWP models PS12 PS19 PS20 PS34 PS35 … Dynamical core Infrastructure Ocean model

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

NCAS supported machines PUMA Pre UM version 9.0 NOC Code repositories Web server (Trac) User /home space UM submission HPC MASS MONSooN File systems: /home, /projects and /nerc Lander Polaris RDF File systems: /home and /work HPC Wales Will talk about version 9 and 10 on Friday Local Jasmin user ssh to all