We are very pleased to have welcomed Philip Mote to the department.
Peter Douglas and Ian MacKenzie will not be presenting their work at the UGAMP meeting but have each prepared a brief description of their current work.
Peter Douglas is continuing his work simulating the volcanic cloud produced by Mt. Pinatubo using inert tracers in the UGAMP models. The EUGCM results show that after a year the tracer mostly remains in the tropics as observed in the real atmosphere. The detrainment of tropical air into the mid-latitudes seen in the form of `tongues' of high aerosol values extending into mid-latitudes is also represented well in the EUGCM. However, compared to observations of the actual cloud, the model is transporting too much tracer into the Northern hemisphere and not enough into the South. The cause of this asymmetry between the two hemispheres is now under investigation.
Ian Mackenzie has run the EUGCM with full chemistry and an ozone-like passive tracer for a 60 day period during the southern spring with a view to estimating the relative contribution of chemical and dynamical processes to ozone change occurring within the polar vortex. Preliminary results indicate that particularly towards the edge of the vortex, ozone in the lower stratosphere is being replenished by diabatic descent on a scale comparable to that of the chemical depletion. More detailed analysis is ongoing, which it is hoped will be of help in reconciling ozone changes observed by MLS within the polar vortices with the chemical destruction rate estimated from the ClO measurements.
Peter Stott