The effect of the 11-year solar-cycle on the temperature in the upper-stratosphere and mesosphere—Part III: Investigations of zonal asymmetry

Abstract

The response to the 11-year solar cycle is investigated using a 3-D mechanistic stratosphere–mesosphere model, in particular the zonal asymmetry in the solar signal. Two model simulations are performed, one using solar forcing corresponding to solar minimum and the other corresponding to solar maximum. It is seen that the solar signal is strongly zonally asymmetric in northern hemisphere winter, with variations of up to 20 K at 25 km. The model results are compared to the solar signal seen from five rocket-sonde sites and one lidar site, all located at mid-latitude, but at different longitudes. Although there are some significant differences between the model results and the observations, the model results help to explain why there are significant variations in the solar signal in the observations made at different longitudinal positions. Such longitudinal dependence obviously does not appear in zonal mean results, hence this raises questions about the meaning of comparing zonal mean model results with results from local observations.