The turbulent flow field characteristics are investigated
using the data of the sonic anemometers (available from 16
July onwards)2 mounted at z/h = 1 and 1.5. The root mean
square (rms) values of vertical velocity fluctuations, sw, are
shown in Fig. 12 together with the diurnal distribution of corn
pollen concentration for 16, 17, 19 and 20 July at z/h = 1 and 2.
Note that instantaneous values of vertical velocity fluctuations
reach much higher levels than the rms values. The
dashed, horizontal line corresponds to the Stokes settling
velocity of corn pollen in still air (Eq. (5)). Comparing the times