The figure shows that when fire spots are not present, the fire ROS (panel C) increases almost linearly with time. In the absence of turbulence (uncoupled), the number of generated firebrands (panel D) also increases linearly with time, whereas when turbulence is present, the firebrand generation varies approximately with the number of generating sources (i.e., points where fire ROS is above the specified threshold). This variation is approximate because the generation interval is longer than the model timestep (fs_firebrand_gen_dt = 5); hence the local maxima of generating sources may not always coincide with a generation cycle.