Opened 12 years ago

Closed 12 years ago

#208 closed help (fixed)

LBC time frequency

Reported by: chollow Owned by: willie
Component: UM Mesoscale Keywords: LBC
Cc: l.steenman-clark@…, g.m.s.lister@… Platform:
UM Version:

Description

We are planning to do some limited area domain runs at 12 km resolution forced with lateral boundary conditions generated directly from UM start dumps (using makebc) rather than using lateral boundary conditions generated by a global model run. However, the actual analysis dumps are only available at most every three hours. Then the LBC file will only have values every three hours (or every six hours for ECMWF analyses), and therefore the 12 km resolution run will experience sudden changes in forcing every three or six hours. Is that correct, or does the UM try to interpolate the boundary conditions in time? If it is correct that the forcing changes abruptly, do you have any idea whether this can cause major problems with the limited area run?

Change History (2)

comment:1 Changed 12 years ago by willie

  • Cc l.steenman-clark@…, g.m.s.lister@… added
  • Owner changed from um_support to willie
  • Status changed from new to assigned

Chris,
You could take one start dump and run the UM in global mode for 15 days to produce an LBC file to drive the LAM of interest. This forcing would become progressively inaccurate as time went on. To improve upon this slightly, you could use start dumps spaced five days apart and produce three LBC files (by running the model three times) to cover the 15 day period. It depends on what you are trying to achieve.
Regards,
Willie

comment:2 Changed 12 years ago by willie

  • Resolution set to fixed
  • Status changed from assigned to closed
Note: See TracTickets for help on using tickets.