Vertical velocity field and convective plumes in the atmospheric boundary layer as observed with an acoustic Doppler Sodar

Résumé : The vertical velocity field and the convective plumes are observed during the morning with the acoustic Doppler sounder of the C.R.P.E.. The study presents two points of view : 1) The macroscopic point of view : the histogram of vertical velocity in the well mixed layer associated with conditional averaging shows the relations between the vertical velocity skewness and the convective velocity w* and gives an objective criterium for plume determination. 2) The microscopic point of view : using TELFORD's 1970 and MANTON's 1975 models, a comparison is made between the predictions of the models and the plumes properties as observed by the Doppler Sodar. It is shown that the convective plumes observed carry near sixty percent of the sensible heat flux at the top of the surface layer.