This proposal addresses the question of whether Solar variability can affect our atmosphere through UV insolation. Effects have been found statistically (LBitzke and Van Loon), but we do not know if these have physical causes or just statiscal "quirks". The effect of solar ultraviolet (uv) insolation variations on the troposphere and stratosphere will be investigated with a General Circulation Modedl extending from the surface to 85 km. Solar uv variations at wavelengths less than 0.3u will be input into the model in three situations: the model control run (which has light cast tropical winds in the lower stratosphere) and the two phases of the QBO (strong east winds and strong west winds). The model simulations for the control, QBO experiments and increased uv experiments will each be run for three years, in an attempt to separate the solar impact from the interannual variability. The uv increase first utilized will be large (50%) to clarify the nature of potential responses. Future experiments will reduce the increase to 10%, and may alter the spectrum of the increase, so that a greater percentage of the change is at the shortest wavelengths. The goal of these experiments is to investgate and understand the potential impact solar cycle variations may have on the troposphere and stratosphere. The stratosphere is most likely to be directly affected, and the method of any potential interaction with the troposphere will be closely examined. Possible tropospheric impacts of interest include variations in jet stream, storm track and the general synoptic climatology, all of which have been reported in the literature but whose mechanism has yet to be identified. Successful simulation of such responses, if they occur, will help validate the observations, as well as the ability of coupled troposphere/stratosphere models to simulate the dynamical interactions between these two regions.
