Sensible heat exchange at the Antarctic snow surface: A study with automatic weather stations

Data of four automatic weather stations (AWSs) are used to calculate the turbulent exchange of sensible heat at the Antarctic snow surface for a 4 year period (1998-2001). The AWSs are situated on the ice shelf, in the coastal/inland katabatic wind zone and on the interior plateau in Dronning Maud Land, East Antarctica. Sensible heat flux (SHF) is calculated using the aerodynamic 'bulk' method between a single AWS sensor level and the surface, in combination with surface temperature derived from upwelling longwave radiation and surface roughness derived from eddy correlation measurements. Good agreement is found between calculated and directly measured SHF. All AWS sites show a downward-directed average sensible heat transport, but otherwise the differences between the various zones are large. The surface roughness for momentum differs by an order of magnitude between the interior plateau (0.02 mm) and the katabatic wind zone (0.16 mm). On the ice shelf, frequent clouds limit surface cooling, and annual mean SHF is small (8 W m^-2). In contrast, clear skies prevail on the interior plateau, but weak winds, an aerodynamically smooth surface and stability effects limit annual mean SHF to an equally low value (8 W m^-2). The most favourable conditions for sensible heat exchange are found in the katabatic wind zone, where a combination of strong winds, relatively little cloud cover and a rougher surface results in annual mean SHF values of 22 to 24 W m^-2.