Use of a diagnostic based on semi-geostrophic theory to understand the behaviour of a comprehensive atmospheric circulation model on large scales
Weather and climate models solve the full classical equations of dynamics and thermodynamics, anything else is far too restrictive. However, the resolution required to solve these equations properly is far out of reach. In addition, understanding and validation of the model solutions is very difficult. The latter issue can be addressed by using simpler models with limited validity in a diagnostic mode, provided that these simple models approximate the general equations accurately under relevant conditions. I illustrate this by using semi-geostrophic theory, which is valid on large horizontal scales, to understand the solutions of the Met Office model on large scales. I will summarise the underlying theory, and present several examples showing that the semi-geostrophic diagnostic gives useful information which may help in designing model improvements.
Mike Cullen, Met Office
https://www.metoffice.gov.uk/research/people/mike-cullen