Currently at ECMWF, Reading, UK.
The benefits of the Met Office variable resolution NWP model for forecasting convection
Article first published online: 21 FEB 2012
© 2012 British Crown Copyright, the Met Office. Published by John Wiley & Sons Ltd
Volume 20, Issue 4, pages 417–426, December 2013
How to Cite
Tang, Y., Lean, H. W. and Bornemann, J. (2013), The benefits of the Met Office variable resolution NWP model for forecasting convection. Met. Apps, 20: 417–426. doi: 10.1002/met.1300
- Issue published online: 4 DEC 2013
- Article first published online: 21 FEB 2012
- Manuscript Accepted: 22 DEC 2011
- Manuscript Revised: 8 NOV 2011
- Manuscript Received: 15 MAR 2011
- variable resolution model;
High-resolution NWP models which can explicitly allow convection (albeit poorly resolved) are usually run in limited-area domains, and are nested inside coarser resolution models with parametrized convection. The mismatch of the grids and model physics at the boundaries of the limited-area fine resolution model can be a major source of model error. Two major issues are the change in the representation of convection (parameterized to explicit) as air enters the fine resolution model and the limited boundary updating frequency. In this paper, a variable-grid, fine-resolution, limited-area version of the Met Office's Unified Model (UM), developed with the aim of addressing this and related problems with nested models is described. In this variable resolution model, the grid size varies smoothly from coarser (but still convection permitting) resolution at the outer boundaries to a uniform fine resolution in the interior of the domain. In this paper we present results from a comparison of this variable grid model with the analogous results from an equivalent nested model set with uniform high-resolution model nested inside a lower resolution one. The comparison is carried out for a number of convective cases. It is found that the variable resolution model gives very similar results to the nested model system in the inner fixed resolution part of the domain away from the boundaries, both in individual case studies and when statistics are aggregated over cases. This gives confidence in the validity of the variable resolution approach. It is shown that the variable resolution model also gives the hoped for benefits of reducing artefacts at the boundaries.