Left: temperature difference between a model atmosphere computed with a microturbulent velocity of ξ = 15 and 2 km s⁻¹, as a function of the logarithm of the Rosseland optical depth. Right: differences in spectral line profiles associated with the change of microturbulent velocity in the model atmosphere from ξ = 2 km s⁻¹ (solid black line) to ξ = 15 km s⁻¹ (dashed red line). The difference spectrum (dotted blue line) was vertically shifted for clarity. Gaussian noise was added to both spectra to simulate a signal-to-noise ratio S/N ∼ 100.