UGAMP
GROUP NEWS
Rutherford Appleton Laboratory News
Work at RAL is currently concentrating on the tropics and subtropics. The UKMO SMM is being used to study interannual variability and its links to the tropical upper stratosphere. Transport of material out of the tropical pipe, and how this is related to the QBO and to stratospheric sudden warmings is under investigation. Sensitivity studies in the region of the tropical stratopause are also being related to the solar cycle and climate. In the sub-tropical upper troposphere and lower stratosphere (UTLS), the mechanisms affecting the exchange of air across the sub-tropical jet are being investigated by use of trajectories, using both UKMO and ECMWF analyses, and model runs of the UM, as part of the EU project TRACAS (Transport of chemical species across the sub-tropical tropopause). Current results indicate that the Hadley circulation may lead to major differences between mid-latitude and sub-tropical exchange.
Papers to Appear
Interannual variability of trace gases in the subtropical winter stratosphere, L.J. Gray and J.M. Russell. To appear in J. Atmos. Sci. This uses HALOE data to show that variability in subtropical trace gas distributions in the lower stratosphere are due to advection by the QBO circulation and not to the erosion by the action of planetary wave mixing.
A model study of the influence of the quasi biennial oscillation on trace gas distribution in the mid and upper stratosphere. L.J. Gray. Submitted to J. Geophys. Res. This uses the SMM to model interannual variations in the distributions of methane and water vapour in the mid and upper stratosphere and shows that the asymmetry about the equator of these features is due to the QBO induced circulation and not to the effects of planetary wave mixing.
A three dimensional study of the evolution of mid-latitude stratospheric intrusions, M.Bithell, L.J.Gray and B.D.Cox. To appear in J. Atmos. Sci., vol. 56 no. 5, March 1999. This paper presents the evolution of tropopause folds from a three-dimensional perspective and shows that tracer transport and mixing in such events is only likely to become well understood in the proper three-dimensional context.
Mike Bithell
Rutherford Appleton Laboratory
m.bithell@rl.ac.uk
