WACCM-X simulation of tidal and planetary wave variability

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Wednesday, May 31, 2017

This book chapter describes the basic physical processes in the thermosphere, or Earth's neutral upper atmosphere, which need to be captured in a physics-based model. Liu, H., 2014: WACCM-X simulation of tidal and planetary wave variability in the upper atmosphere. Modeling the Ionosphere-Thermosphere System, J. Huba, R. Schunk, and G. Khazanov, Eds., Geophysical Monograph Series, American Geophysical Union, Washington, 181-200 doi:10.1002/9781118704417.ch16.

Teleconnection pattern derived from WACCM-X simulations image
Teleconnection pattern derived from WACCM-X simulations demonstrates the coupling of the whole atmosphere, from the ground to the upper thermosphere. The figure shows the correlation coefficients between zonal mean temperature with winter polar temperature at 10hPa for (a) December-February and (b) June-August periods. Solid contour lines are for positive correction (contour interval: 0.1). Shaded: Statistically significant at 95% level (Liu, 2014)

The thermosphere is the medium from which the ionosphere is created, and the neutral dynamics and composition is an important driver of the ionized component. The ionosphere, in turn, has important impacts on the neutral medium through ion drag and Joule heating.

The frequent collisions of a gas close to thermal equilibrium enable the Maxwellian energy distribution of the individual particles to be replaced by the basic fluid properties of pressure, temperature, number density, and mass density. The continuity equation is also one of the most widely used and universal fluid concepts. Atmospheric models typically solve the equations in an Eulerian coordinate system fixed with respect to the Earth. The chapter talks about the Coriolis effect, neutral composition, and thermal expansion.