Top panels: CO and N₂ snowlines and snow surfaces shown on top of disk-temperature profiles. The striped regions show the constraints on the inner and outer N₂H⁺ edges from the “jump and drop” model, interpreted as the CO and N₂ midplane snowline locations. The blue filled regions mark the temperatures between CO and N₂ freeze-out, extracted from a second grid of parametric models. Note the excellent agreement. Lower panels: χ² surfaces showing model constrains on R1 (inner edge) and R2 (outer edge) in the “jump and drop” model for each disk. The contours correspond to the 1σ–3σ uncertainties.