Tropospheric Temperatures and Southern Hemisphere Circulation

Abstract This note documents improvements in the Southern Hemisphere midlatitude circulation associated with a revised convective scheme that was implemented in a version of the NCAR Community Climate Model. Perpetual July and January runs are performed for a standard control and an experiment with a revised convective parameterization. No other boundary conditions in the model are changed (e.g., sea-surface temperatures or sea ice, which are prescribed from observations). The most notable result is a warmer troposphere at all latitudes that is closer to the observed than to the control. Since the warming is greatest in the tropics, the equator-to-pole temperature gradient is increased in both July and January. As a consequence, the midlatitude u wind maximum is stronger at both times of the year in the lower and mid-troposphere. Sea-level pressure is also lower at high southern latitudes in the circumpolar trough surrounding Antarctica. Greatest improvements of the Southern Hemisphere (SH) circulation in...