Linkages between the cold summer mesopause and thermospheric zonal mean circulation



[1] We present the first results from the NCAR thermosphere/ionosphere/electrodynamics general circulation model (TIE-GCM) coupled to a weather forecast/assimilation system of the lower and middle atmosphere. Our results emphasize the importance of a proper representation of the latitudinal temperature variation at the base of the thermosphere for calculating zonal mean zonal winds in the thermosphere. The inclusion of a realistic cold summer mesopause yields significantly improved agreement with climatology in the calculated thermospheric winds in the summer hemisphere. Having established this link between the temperature structure of the mesosphere and the thermospheric circulation, we next present observational evidence that the year-to-year variability of thermospheric winds can be linked to analogous variations in the onset of the cold summer mesopause season. Since these mesopause variations have previously been ascribed to stratospheric weather variability, by extension, our results suggest a new mode of coupling between the stratosphere and thermosphere.