Dr. Malcolm Roberts

Met Office Hadley Centre

10am, 16 Oct. 2014

Room 303, IAP Keyan Building

Abstract

A traceable hierarchy of global climate models, with atmosphere resolutions (using the Met

Office Unified Model) ranging from 130km to 12km, with a subset of these coupled to ?? ocean (NEMO), have been developed in order to study the impact of improved representation of small scale processes on the mean climate, its variability and extremes.

An ensemble of 25km atmosphere integrations, using time on the European PrACE supercomputer HERMIT, and integrations with the 12km atmosphere model in which the convective parameterization has been switched off, have also been completed.

The UPSCALE project on PrACE made use of 120M core hours during 2012 in simulating an ensemble of 25km atmosphere integrations. Some results from these simulations will be shown, including improved tropical cyclone variability (particularly in the Atlantic), and some particularly exciting results on large-scale hydrological transports and the impact of model resolution.

Building on this work, several 12km simulations have been performed in which the convective parameterization has been either reduced in effect or switched off and replaced by a sub-grid scale turbulence model. The impact on aspects of the simulation, such as the diurnal cycle and propagation of convective systems, will be discussed.

In addition to global climate modelling, there is continuing work to use the UM regional model at convection-permitting scales of 1.5km to study extremes of precipitation over the UK. The rainfall characteristics are changed significantly at such resolutions, and this may have important consequences for future predictions of extreme rainfall.

There will also be some discussion of future plans, including a proposed HighResMIP as part of CMIP6, and coupled modelling using an eddy-resolving ocean at 1/12?.