Solar impact on the lower mesospheric subtropical jet: A comparative study with general circulation model simulations

Abstract

The seasonal and interannual variation in the lower mesospheric subtropical jet (LMSJ) and their dependence on the 11-year solar cycle are studied by comparing observational data with simulations by two general circulation models. In the model simulations, a strengthening of the LMSJs is found in both hemispheres during the winter under the solar maximum condition, similar to the observation. However the model responses are substantially smaller except for one case in the southern hemisphere. It is also found that the stronger LMSJ due to an enhanced solar forcing appears during the period which follows an increasing period of interannual variation. Analysis of the observed seasonal march of the LMSJ in each year shows two different regimes of behavior. For a successful simulation, the model should realistically reproduce the observed interannual variability as well as the climatological mean.