On the determinants of the near surface temperature regime on the South Polar Plateau

Abstract

Most studies of the physical climatology of the Antarctic interior focus on the local surface energy budget. The results of these studies are reviewed leading to the often cited conclusion that atmospheric heat transport is required from lower latitudes to maintain the temperature against the large radiative losses by the snow‐atmosphere system of the interior plateau. Micrometeorological data taken over a 3 year period at the south pole are presented, illustrating the annual cycle of the surface energy budget. In addition, these data, coupled with local 500 mbar data, are used to examine the role of vertical and horizontal transport mechanisms in determining the near‐surface temperature variations. The major conclusions are as follows. The interannual variability in the radiation budget components is very small. Day to day variations in the longwave and sensible heat flux are high and related to variability in the synoptic conditions such as cloudiness, wind flow at the surface, and wind and temperature variations at 500 mbar. Except during the summer season, the variability in surface temperature is highly correlated with wind speed, which in turn is strongly correlated with wind direction. Down slope flows are generally low speed and associated with cooling. Cross slope and up slope flows are generally stronger and associated with warming. In summer, there is no correlaton between local temperature and surface wind speed, but down slope flows are generally associated with local cooling. Horizontal thermal advection in the lower troposphere has a very pronounced effect on the surface temperature in summer but only a moderate to weak effect in the other seasons. Except in summer, strong winds (i.e., cross and up slope winds) are associated with weakened thermal stratification; weak winds (down slope) are associated with increased thermal stratification. In addition to the radiation budget, downward mixing through the boundary layer and transient horizontal advection appear far more important than local divergence or convergence effects in determining the local temperature.