HAO Colloquium - Jens Oberheide, Clemson University

The tidal weather of Earth’s middle and upper atmosphere

A variety of weather processes in the troposphere, solar radiation absorption in stratospheric ozone and nonlinear wave-mean flow interactions excite a longitude-dependent spectrum of atmospheric tides – global scale wave motions – with periods defined by Earth’s rotation rate. Growing exponentially in magnitude when propagating upward, tides are a key ingredient in coupling the lower with the upper atmosphere. Tides carry vast amounts of energy to the thermosphere-ionosphere, modify dynamo processes, and substantially change the mean state of the thermosphere-ionosphere including circulation, chemical composition, energy budget, and plasma densities. While the community has made significant progress in understanding the morphology, variations and impacts of tides on seasonal timescales (“tidal climate”), tidal variations on timescales of days or weeks (“tidal weather”) are much less understood, mainly due to constraints imposed by the observing geometries of current satellites that do not allow one to fully resolve the frequency/wavenumber spectrum with a few days time resolution. The talk will present new data analysis approaches of SABER/TIMED data to attack the problem, comparisons with state-of-the-art modeling such as WACCM+DART, and a discussion of the impact of recurring weather patterns such as the Madden-Julian Oscillation and wave-wave interactions on the tidal weather of Earth’s middle and upper atmosphere. Preliminary results from the new GOLD mission indicate a rather large response of the mean state of the thermosphere during periods of enhanced tidal wave driving, an effect that was predicted by models but could not be observed before.


Date and time: 
Friday, October 25, 2019 - 2:00pm to 3:00pm