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Partial farewells to: Rowan Sutton, who has finished his DPhil thesis and has moved over to work with David Anderson (also in Oxford) on Ocean-Atmosphere coupled modelling and Nayna Prajapati, our NERC programmer, who has moved over to work with the ISAMS team.
Welcome to two new DPhil students: Alan Iwi, who is working with Warwick Norton and David Andrews on a UGAMP studentship on use of ISAMS tracer data to improve assimilation of stratospheric winds in low latitudes, and Euain Drysdale, working with David Andrews on a NERC studentship on QBO modelling.
Warwick Norton has spent the past three months working at NCAR.
Marzieh Fatemian will return from maternity leave shortly.
In September, David Andrews spent three weeks visiting Bob Vincent's group in the Department of Physics, University of Adelaide, where he learnt a great deal about recent radar and balloon measurements of gravity waves. He spent some time thinking about the thorny problems of extracting gravity-wave information from such measurements. He also met up with David Karoly and paid a brief visit to Kip Marks, who now works at the Cooperative Research Centre for Southern Hemisphere Meteorology at Monash University and the Bureau of Meteorology, Melbourne.
David Andrews
In attempting to interpret some of the features seen in the ISAMS stratospheric temperature and horizontal wind fields during the northern hemisphere winter (documented in Rosier et al. (1994)), the UKMO Stratosphere-Mesosphere Model has been used, initialised with ISAMS temperature and with UKMO SSU data providing the lower boundary geopotential height field. A generally good simulation is found to help elucidate some of the processes occurring during the ISAMS period. In particular, model vertical velocity fields have been produced and studied, providing a fuller Eulerian view of the evolution through this period that was possible from the observations alone.
Most recently, a set of model experiments has been performed which utilises the fact that the lower boundary is supplied from observational data. Various idealised boundary forcing have been applied: the same observations but with planetary wave amplitudes doubled and halved, and the observations kept fixed following days when wave-one and wave-two (separately) were enhanced. Many interesting results have been found; for example a constant wave-one lower boundary forcing leads to a strong major warming about a month earlier than the near-major warming in the 'control' simulation, whereas a constant wave-two lower boundary forcing leads to a substantially more quiescent stratospheric winter. Vertical velocity fields and the thermodynamic energy budget in these model experiments are also being investigated.
Helen Rogers (NERC student) has been using the technique of contour advection, together with ISAMS aerosol extinction data, to study the transport of tracers from the tropics into middle latitudes.
Suzanne Rosier
Rosier, S.M., Lawrence, B.N., Andrews, D.G. and Taylor, F.W. (1994). Dynamical evolution of the northern stratosphere in early winter 1991--92, as observed by the Improved Stratospheric And Mesospheric Sounder. J. Atmos. Sci., 51, 2783--2799.
Ruth, S.L., Remedios, J.J., Lawrence B.N. and Taylor, F.W. (1994). ISAMS measurements of N2O during the early northern winter 1991--92. J. Atmos. Sci., 51, 2818--2833.
Sutton, R.T., Maclean, H., Swinbank, R., O'Neill, A. and Taylor, F.W. (1994). High-resolution stratospheric tracer fields estimated from satellite observations using Lagrangian trajectory calculations. J. Atmos. Sci.,51, 2995-3005.
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