Sudden Stratospheric Warming

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University of New Brunswick


Science of the Middle and Upper Atmosphere is relatively young, mostly because we were only able to take direct measurements of observable quantities (winds, temperatures etc.) at such high altitudes; with the aid of some of the recent sophisticated technological advances i.e. satellites, radars and such. Even with the aid of these expensive tools it is hard to sample the whole atmosphere, and explain complex properties that our atmosphere exhibits. Models are one of the tools which bridge the gap between the observations and the physical processes involved. In the past few decades with the fast advancements of computers and super-computers, scientists all over the world have been able to explain some atmospheric phenomena and develop new theories using different atmospheric models. These models are highly complex computer codes that run on very powerful computers, and they incorporate the physical processes thought to exist in the real atmosphere. One such model is the Canadian Middle Atmosphere Model (CMAM), which has proven to be one of the best in the world. My thesis will consist of using the data generated by CMAM to try to explain the phenomenon known as a Sudden Stratospheric Warming (SSW). SSWs have been observed for several decades in the Northern Hemisphere, but it became an especially popular topic among atmospheric physicists after the Ozone hole splitting above Antarctica in 2002, for which a major SSW was thought to be responsible. This was the first major SSW observed in the Southern Hemisphere. My thesis will mainly concentrate on the model Northern Hemisphere winter, where a warming occurred in the model. January, February, and March CMAM data will be analyzed thoroughly to detect any disturbances in the wave and tide patterns of the atmosphere. Quantities analyzed will include temperatures, winds, geopotential, Elliasen Palm (EP) flux, Matsuno refractive index (RI), gravity waves and atmospheric tides. Analysis to date shows that a SSW appears at the end of January in the model and lasts for about 20 days. Major Stratospheric Warmings involve anomalous planetary wave propagation to and dissipation in the polar stratosphere and typically increase the temperature of the stratosphere by as much as 40 - 50 K. This is very significant and it plays a big role in the energy-momentum budget of the atmosphere. Associated with the SSW are also thought to be mesospheric coolings, and recently discovered thermospheric warmings. In this thesis, l will examine correlations between the large scale features of this warming and wave variations and diagnostics of the dynamics.