Figure 4.

Predicted distribution of fallout times, P(t), for aphids that cease flying when at a height of 100 m and within (a) a convective boundary layer with wind shear (u_*=0.3 m s⁻¹ and w_*=2.0 m s⁻¹), (c) a boundary layer of intermediate stability (u_*=0.4 m s⁻¹ and w_*=1.0 m s⁻¹) and (d) a boundary layer of neutral stability (u_*=0.8 m s⁻¹ and w_*=0.5 m s⁻¹). The mean fallout times are (a) $\overline{t}=467\text{s}$, (c) $\overline{t}=302\text{s}$ and (d) $\overline{t}=202\text{s}$; the mean distances travelled downwind are (a) $\overline{x}=0.8\text{km}$, (c) $\overline{x}=1.1\text{km}$ and (d) $\overline{x}=1.7\text{km}$ and the maximum distance travelled are (a) x_max = 15.7 km, (c) x_max = 25.9 km and (d) x_max=38.5 km. (b) Example of predicted trajectories of passively advected non-flying aphids in a convective boundary layer with wind shear.