March 2014 UM Limited Area Models What constitutes a LAM How to set one up in the UM How to start a LAM How to keep a LAM going Nesting LAMS Cascade example

March 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

March 2014 UM LAM

March 2014 UM LAM 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

March 2014 UM LAM

March 2014 UM LAM Start file obtained by reconfiguring from a lower resolution model – LAM or global ancillary files may be required when changing resolution CAP (central ancillary program) Limited files ( No guaranteeshttp://met.reading.ac.uk/~grenville/CAP_INTERFACE45/cap_general.php

March 2014 UM LAM Start file Reconfiguration Start file Ancillary data (target domain) At source resolution, global or LAM At target resolution, for target domain

March 2014 UM LAM Lateral Boundary Conditions obtained from a model run at lower resolution OR makebc – utility that creates lbcs from start files or fields files with appropriate stash fields

March 2014 UM LAM Lateral Boundary Conditions obtained from model run at lower resolution OR makebc Same as before when defining the LAM domain

March 2014 UM LAM Target model (Source model for next step) Start fileLateral Boundary Conditions Source model ReconfigurationAncillary files (target domain) makebcFields file Nesting

March hrly 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?

March km 4km1.5km