Dust-to-gas density ratio at t = 400 T₀ from models with different reference Stokes numbers. The left and right columns correspond to models with α = 10⁻⁴ and 10⁻⁵, respectively. Upper panels: Results from the fiducial reference Stokes number St₀ = 10⁻³. Lower panels: Models with St₀ = 10⁻². Dashed curves denote contours for 25% of the gas scale height, and arrows below denote the Stokes number of dust grains in the midplane. The spatial domains differ between the upper and lower panels due to the different radial drift timescales.