NCAS Unified Model Introduction Part 1 a Overview

NCAS Unified Model Introduction Part 1 a: 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. 2

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 (vn 6. 6. 3 or earlier only e. g. Had. GEM 2) 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

© Crown copyright Met Office 4

Global & regional NWP system Parallel suite 35 Global 17 km 70 levels (N 768 L 70) EURO 4 km 70 levels UKV 1. 5 km 70 levels [Retired NAE 12 km 70 levels] © Crown copyright Met Office 5

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 6

Global models (at mid-latitudes) • Fixed resolutions: N 96 N 144 N 216 N 320 N 512 N 768 (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° x 0. 83° x 0. 56° x 0. 375° 0. 35° x 0. 234° x 0. 16° • Common scientific configurations used across scales (weather, seasonal and climate): o o o 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. 7

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

NWP v Climate models NWP Climate Run length 5 day operational forecast, 15 day ensemble forecast Months (seasonal) Years, decades, centuries+ Global resolution Testing: N 320 (40 km) with 15 min ts Low resolution: N 96 (135 km) with 20 min ts Operational: N 768 (17 km) with 7. 5 min ts High resolution: N 512 (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 9

Had. GEM 2(-ES) Had. GEM 2 -ES Physical climate • Full Earth system model • Development completed in 2009 • Used for IPCC AR 5 (CMIP 5) • N 96 – 1° ocean Aerosols and chemistry (UKCA) Ocean biogeochemistry Interactive vegetation (TRIFFID) Other versions available: • -A (atmosphere only) • -AO (coupled atmosphere-ocean) • -CC (carbon-cycle) Earth system minus UKCA Human emissions 10

Had. GEM 3(-AO) Under continuous development. There are versions with: • different code releases • different scientific configurations Multiple resolutions: • N 96 – ORCA 0. 25 • N 216 – ORCA 0. 25 • N 512 – ORCA 0. 25 / ORCA 12 (experimental) UM atmosphere (GA) JULES land surface (GL) OASIS 3 coupler NEMO ocean model (GO) CICE sea ice (GSI) Can run atmosphere-only (Modified from a Met Office diagram. ) 11

Other modelling systems • MOGREPS: ensemble forecast – Based on Parallel Suites • Glo. Sea: seasonal prediction – Based on Had. GEM 3 coupled model with NEMO-CICE • De. Pre. Sys: decadal prediction – Based on Had. CM 3 (due to be upgraded to Had. GEM 3) 12

Terminology Model version: defines the code base used. Model configuration: defines the science options, eg GA 6. 0, GO 5. 0. Modelling system: application with specific configuration (eg Had. GEM 3 -GC 2, Glo. Sea 5). Parallel suite: version of operational forecast system Job: particular instance defined and run by user Experiment: grouping of jobs in UMUI 13

Major UM developments Old 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 PS 34 PS 35 Climate models Had. CM 3 Had. GEM 1 Had. GEM 2 Had. GEM 3 NWP models PS 12 Dynamical core PS 19 Infrastructure PS 20 … Ocean model 14

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

NCAS supported machines PUMA Pre UM version 9. 0 Code repositories Web server (Trac) User /home space NOC UM submission Lander Polaris HPC MONSoo. N HPC Wales File systems: /home and /work File systems: /home, /projects and /nerc MASS RDF Local user ssh to all Jasmin 16