Vertical profiles of biological particle concentrations under convective conditions

Measurements of vertical profiles of pollen concentration from local and remote sources have been made during convective conditions with balloon-mounted rotating impaction samplers.The vertical profiles of local particles appear to be usually characterized by a decrease in the ground layer and by almost constant values aloft. A minimum often occurs at levels between 100 and 200 m.The concentration profiles of pollen from remote sources present a peak at heights of some hundred meters.By comparing the observed profiles with some published models of transport, it appears that: (i) because of differing eddy scales, turbulent transport affects the settling of pollen differently close to the ground than aloft; and (ii) turbulent anisotropies related to the dynamic and thermal structure of the atmosphere may affect the vertical distribution of particulate matter in the boundary layer.