For example, on17 July from0900 to 1000 EDT,highpollen
concentrations were sampled at z/h = 1 while sw was relatively
low 0.1–0.2ms1, close to the presumed threshold level of
becoming airborne. Such a low level would limit the vertical
upward transport of the pollen grains as indicated by a lowratio
of c(z/h = 2)/ch. As the wind picked up and the magnitude of
sw increased, the fraction of emitted pollen at canopy height
that reached twice this height, c(z/h = 2)/ch, increased.