A GENERAL-CIRCULATION MODEL STUDY OF THE SOLAR AND QBO MODULATION OF THE STRATOSPHERIC CIRCULATION DURING THE NORTHERN-HEMISPHERE WINTER

A general circulation model has been used to study the modulation of north-polar temperatures during winter by both solar activity and the equatorial quasi-biennial oscillation (QBO). The variation of solar activity was simulated by changing the heating rate due to the absorption of ultraviolet (UV) radiation by ozone, while the QBO zonal wind fields were reproduced by incorporating zonal-momentum sources in the equatorial stratosphere. A total of 10 experiments were conducted by changing the heating rate from 70 to 110% for each of the simulated QBO easterly and westerly cases. The results of the numerical experiments show modulation effects similar to those found by Labitzke [1987] in the 30-mb temperatures at the North Pole.