NCAS Unified Model Introduction Part 4b: UM Limited Area Models University of Reading, 3-5 December 2014

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 2

3 UMUI configuration

4 Obtained from CAP or reconfiguration Used to put equator of rotated grid In the centre of the LAM domain LAMPOS or BADC Grid utilities Lat, lon in rotated grid UMUI configuration

An example LAM 5

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): 6

Start files Start file Reconfiguration Start file Ancillary data (target domain) At source resolution, global or LAM At target resolution, for target domain 7

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 8

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

Workflow Target model (Source model for next step) Start file Ancillary files (target domain) makebcFields file Nesting 10 Source model Reconfiguration Lateral Boundary Conditions

6hrly ECMWF analyses UM reconfiguration makebc 40km makebc 12km 40km ancillary 40km reconfig 40km model 12km ancillary 12km reconfig 12km model 4km reconfig 4km ancillary 4km model 1.5km ancillary 1.5km model 1.5km reconfig Sub-domains? 11

12km 4km 1.5km