1. Part 1a: Overview of the UM system
University of Reading, March 2015

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.
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

4. © Crown copyright Met Office

5. 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

6. 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

7. 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.

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

9. 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

10. 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

11. 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.)

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)

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

14. 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

15. 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

16. 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