UM Limited Area Models What constitutes a LAM

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 Lat, lon in rotated grid Used to put equator of rotated grid In the centre of the LAM domain LAMPOS or BADC Grid utilities Obtained from CAP or reconfiguration 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) http: //met. reading. ac. uk/~grenville/CAP_INTERFACE/cap_general. php Limited files (http: //met. reading. ac. uk/~grenville/CAP_INTERFACE 45/cap_general. php) No guarantees March 2014

UM LAM Start file Reconfiguration Start file At source resolution, global or LAM Ancillary data (target domain) 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 Source model Ancillary files (target domain) Reconfiguration Start file makebc Fields file Lateral Boundary Conditions Target model (Source model for next step) March 2014 Nesting

6 hrly ECMWF analyses UM reconfiguration makebc 40 km ancillary makebc 12 km 40 km reconfig 40 km model 4 km ancillary 12 km reconfig 12 km ancillary 12 km model 4 km reconfig 4 km model 1. 5 km ancillary 1. 5 km reconfig 1. 5 km model March 2014 Sub-domains?

12 km 4 km March 2014 1. 5 km