Heat and water vapour fluxes and scalar roughness lengths over an Antarctic ice shelf

We present eddy-correlation measurements of heat and water vapour fluxes made during the Antarctic winter. The surface layer was stably stratified throughout the period of observation and sensible heat fluxes were always directed downwards. However, both upward and downward water vapour fluxes were observed. Their magnitude was generally small and the latent heat flux was not a significant fraction of the surface energy budget. The variation of heat and water vapour fluxes with stability is well described by Monin-Obukhov similarity theory but the scalar roughness lengths for heat and water vapour appear to be much larger than the momentum roughness length. Possible explanations of this effect are discussed.