Post on 18-Jan-2018
description
NCAS Unified Model Introduction
Part 4b: UM Limited Area Models
University of Reading, 3-5 December 2014
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UM LAM
• Model whose domain does not span the entire globe• It will have boundaries in both EW and NS directions eg the NAE, UK MES – operational• Same physics as the global model• Differing resolutions
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UMUI configuration
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Obtained from CAP or reconfiguration
Used to put equator of rotated gridIn the centre of the LAM domainLAMPOS or BADC Grid utilities
Lat, lon in rotated grid
UMUI configuration
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An example LAM
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Start files
Obtained by reconfiguring from a lower resolution model: • LAM or global• Ancillary files may be required when changing resolution• CAP (central ancillary program):
http://www.met.reading.ac.uk/~grenville/CAP_INTERFACE/cap_general.phphttp://www.met.reading.ac.uk/~grenville/CAP_INTERFACE45/cap_general.php
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Start files
Start file
Reconfiguration
Start file
Ancillary data(target domain)
At source resolution, global or LAM
At target resolution, for target domain
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Lateral Boundary Conditions
These are obtained from a model run at lower resolution OR makebc – a utility that creates LBCs from start files or fields files with appropriate stash fields
These are obtained from a model run at lower resolution OR makebc – a utility that creates LBCs from start files or fields files with appropriate stash fields
Lateral Boundary Conditions
Same as before when Defining the LAM domain
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Workflow
Target model(Source model for next step)
Start file
Ancillary files(target domain)
makebc Fields file
Nesting
Source model
Reconfiguration
Lateral Boundary Conditions
6hrly ECMWF analyses
UM reconfiguration
makebc 40km makebc 12km
40km ancillary 40km reconfig
40km model
12km ancillary12km reconfig
12km model
4km reconfig4km ancillary
4km model
1.5km ancillary
1.5km model
1.5km reconfig
Sub-domains? 11
12km
4km 1.5km