Lance Thomas

Personal Profile

Educated at Port Talbot Grammar School, Professor Thomas graduated in Physics from the University of Wales, Swansea, and completed a PhD in ionospheric physics. He spent more than twenty years on research in this area at the UK Appleton Laboratory and the US NOAA Environmental Research Laboratories. He joined Aberystwyth University, in 1981 and served as Professor and Head of Department until 1994, Research Professor until 1997, and continues as Emeritus Professor. He is an authority on theoretical and experimental studies of the atmosphere and ionosphere for which he was awarded the DSc degree in 1972 and the Charles Chree medal and prize of the Institute of Physics in 1991. He has pioneered a number of laser radar (lidar) techniques now adopted as standard methods for atmospheric measurements, and was responsible for the establishment of the major radar system operated as a NERC facility near Aberystwyth. These two types of experiments have formed the basis of his research into gravity waves and turbulence in the middle atmosphere during the past decade. He has been a member of boards and committees of ESA, NASA, SERC, PPARC, NERC, the British National Space Centre and the Royal Society, and is a member of the Council of the Institute of Physics. He is a Fellow of the Royal Meteorological Society and of the Institute of Physics. His outside interests range from golf to music and modern history.

Research Interests

Theoretical and experimental studies of the middle atmosphere since 1982

A major part of the studies of the middle atmosphere, at heights between about 2 and 100 km, have been based on observations with laser radar (lidar) systems and the mesosphere, stratosphere and troposphere (MST) radar facility of NERC, located near Aberystwyth. This facility was developed and built jointly by the Department of Physics at Aberystwyth and the Rutherford Appleton Laboratory. A total of eight PhD's have been awarded on these studies since 1981.

Part of the lidar observations have been directed towards particular atmospheric features or parameters, such as the stratospheric aerosols injected during the eruption of volcanoes such as El Chichon, in Mexico, the height variation of temperature up to about 95 km, the height variation of ice crystals associated with cirrus clouds and their orientation about the horizontal plane, and the presence of ice crystals near the mesosphere, at about 85 km altitude, in summer and associated with noctilucent clouds. However, a major application of the lidar and also of the MST radar has been concerned with studies of the characteristics and vertical propagation of atmospheric gravity waves. Particular attention has been paid to waves generated by low level winds passing over mountains and by the jet stream at about 10 km altitude. An important consideration in these studies has been the mechanisms of wave absorption, dissipation and reflection which determine the vertical extent of these waves, as viewed by the radar up to about 20 km and by the lidar systems at greater heights, up to about 70 km. A related subject of study has been the generation of turbulence associated with these waves, as shown by radar measurements. Criteria for identifying turbulent structures have been developed and such structures have been examined at tropospheric, lower stratospheric, and mesospheric heights. The phenomena of waves and turbulence are of intrinsic interest in themselves but the recognition of their roles in determining the general circulation of the middle atmosphere and mixing processes, and hence the transport of constituents, has inspired widespread studies in which lidar and MST radars have made unique contributions.

The theoretical studies have been largely concerned with the height distributions of neutral and ionized constituents in the region between 60 and 100 km. Modelling studies have provided information on the height distributions of neutral constituents such as atomic oxygen, water vapour and ozone. These results have been incorporated in parallel studies of the atomic sodium layer produced by meteoric ablation, of negative ions and their roles in day to night changes of the ionospheric D region, and of the excitation of atomic and molecular airglow emissions.

Recent Publications

  • Applications of the NERC MST radar facility in mesoscale studies, Meteorol. Appl., 6, 133-142, (1999).
  • Thomas, L., Worthington, R.M. & McDonald, A.J., Inertia-gravity waves in the troposphere and lower stratosphere associated with a jet stream exit region, Ann. Geophysicae, 17, 115-121, (1999).
  • Hooper, D.A. & Thomas, L., Complementary criteria for identifying regions of intense atmospheric turbulence using low vhf radar, J. Atmos. Solar-Terr. Phys., 60, 49-61, (1998).
  • McDonald, A.J., Thomas, L. & Wareing, D.P., Night-to-night changes in the characteristics of gravity waves at stratospheric and lower mesospheric heights, Ann. Geophysicae, 16, 229-237, (1998).
  • Thomas, L., Sir Granville Beynon, Biog. Mems. Fell. R. Soc. Lond., 44, 51-62, (1998).
  • Worthington, R.M. & Thomas, L., The frequency spectrum of mountain waves, Q.J.R. Meteorol. Soc., 124, 687-703, (1998).