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Seminar: Wednesday, February 23, 2011 at 3:30pm

Solar Forced Thermal Tides in the Atmosphere
Dr. Jian Du-Caines
University of Cambridge, UK

While gravitationally forced lunar tides generate significant amplitude periodic oscillations in the global oceans the corollary is not true for the atmosphere. In fact the lunar tides in the atmosphere are quite small in comparison to the thermally forced solar tides. These atmospheric tides are forced by the periodic absorption of solar radiation in the infra-red by water vapor in the troposphere and the ultraviolet by ozone in the stratosphere. Conserving energy and propagating vertically through the atmosphere these waves can reach significant amplitudes of 30-50 m/s in the horizontal wind field and 10-20K in the temperature field of the mesosphere before breaking or dissipating. This provides a mechanism for the redistribution of energy throughout the atmosphere.

In this talk I will provide a brief overview of the solar forced atmospheric tides, results from current modelling efforts and discuss recent observations from space and ground-based instruments. One of the potential generation mechanisms for the atmospheric tides – non-linear interactions between waves and the transport effect of atmospheric waves in the mesosphere are also briefly discussed.

Location: Physics Bldg., Room 401