CHARACTERISTICS OF THE BOUNDARY-LAYER THERMAL STRUCTURE AT A COASTAL REGION OF ADELIE LAND, EAST ANTARCTICA

The boundary layer thermal structure, observed through Doppler sodar, at Dumont d'Urville, has been analysed. Typical echograms of the spiky layers, wavy layers and thermal plumes, except for the eroding invers ion, have been observed. The annual distribution of these thermal stru ctures is presented. The spiky layers are observed to coincide with st rong winds (mainly katabatic) flowing from the inner continent sector, 90 degrees-180 degrees. The upper boundary of the spiky layers is cor related to the wind direction; the maximum depths (more than 400 m) ar e confined to 60 degrees wide span centred at 135 degrees. The predomi nant waves and the spiky layers, tend to occur alternately in accordan ce with the relative dominance of the katabatic flow intensity and the stability conditions. The sodar signatures of these structures are ex amined in relation to the onset and dissipation time, duration and the seasonal distribution. Both waves and spiky layers occur at any hour of the day; their maximum occurrence is in winter months. The persiste nce of the waves varies from a couple of hours to a couple of days whi le the spiky layers can occur for periods even longer than 3-4 days. T he characteristics of these phenomena are associated with the diurnal radiational cycle and the temperature contrast in proximity to the coa st.