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