An improved version of UCL's CMAT2 GCM with meteorological forcing
David Johnson
University College London
Recent research has established numerous links between dramatic meteorological events such as Sudden Stratospheric Warmings (SSWs), and variability in the upper atmosphere. In order to investigate the sensitivity of the MLT region to winds, waves, and tides generated in the troposphere and stratosphere, we have been developing techniques to drive UCL’s Coupled Middle Atmosphere and Thermosphere (CMAT2) GCM with a series of meteorological models and reanalyses.

Three such models are the ECMWF ERA-I reanalysis, the NRL NOGAPS alpha reanalysis, and the UK Met Office Unified Model. In this study we couple these models with CMAT2 using Newtonian Relaxation in the overlapping lower/middle atmosphere regions. We demonstrate the variability imposed on the MLT region through a more realistic lower atmosphere representation when compared with the use of parameterised tidal and gravity wave schemes commonly used in GCMs. By running an ensemble of simulations, we show the sensitivity of the MLT region to different events such as SSWs before, during, and after the onset of such events. Furthermore, we can run a ‘forecast mode’ to investigate how migrating and non-migrating tides during both ‘quiet times’, and proven vertical coupling events influence the behaviour of the MLT region.