∆p is essential for ensuring sufficient overlap between different puffs, which is particularly crucial when wind direction changes significantly. Fig. illustrates the transport path of two adjacent puffs created at time t j and t j+1 = t j + ∆p under a varying wind condition. Adequate overlap requires that the rate of change in wind direction, θ j , between the two adjacent puffs, does not exceed half of the spread angle, α j , of the puff created at t j . That is ∆p * ω j = θ j ≤ α j 2 (9)