NCAS

Unified Model Introduction

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.

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• 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

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4 © Crown copyright Met Office

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 35

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

Global models

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• 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.

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°

(at mid-latitudes)

Vertical resolutions

8 © Crown copyright Met Office

Standard resolutions Defined by model levels and height

Example: L85 with top at 85 km

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).

9 Based on information from Dan Copsey

HadGEM2(-ES)

HadGEM2-ES

• Full Earth system model

• Development completed in 2009

• Used for IPCC AR5 (CMIP5)

• N96 – 1° ocean

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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

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)

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)

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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

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Major UM developments

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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

…

Atmosphere model Dynamical core Physics parameterisations Diagnostics (STASH) [JULES and/or UKCA]

UM software

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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

NCAS supported machines

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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

Pre UM version 9.0

NOC