WACCM simulations of the mean circulation and trace species transport in the winter mesosphere

Species with sources in the mesosphere and lower thermosphere, such as nitric oxide and carbon monoxide, can be locally enhanced in the polar region. We investigate the origin of the downwelling air and the timescale for transport using the Whole Atmosphere Community Climate Model (WACCM).

Analysis of the middle atmosphere transformed Eulerian mean (TEM) circulation, also called the residual circulation, is presented. This circulation gives the net air motion in the meridional and vertical directions due to the combined effects of the zonally averaged winds and the wave transport. The summer to winter circulation in the upper mesosphere during the solstice seasons includes strong upward motion at the summer pole and downward motion at the winter pole.