An observational study of entraining convection using balloon-borne turbulence probes and high-power Doppler radar

Features associated with the upper limit of convection, observed by turbulence probes supported by a tethered kite balloon and by high-power Doppler radar, are described. The observations illustrate the interaction of thermal plumes with the capping inversion (and stable air aloft) and confirm the existence of non-turbulent, intermittently turbulent and fully turbulent layers. Evidence is presented for entrainment processes occurring on scales ranging from a few metres to several hundred metres. Individual distortions of the inversion interface, tracked by the radar, have a lifetime of about 5 minutes. Other, larger scale (i.e., > 1 km) perturbations of the top of the boundary layer were observed over longer periods, and are thought to be due to topographical effects.Now at the Meteorological Office, Bracknell, U.K.