Optical-depth dependence of temperature, LOS velocity, and magnetic field strength averaged over 44 peripheral umbral dots (top three panels) and 23 central umbral dots (bottom three panels). The error bars denote standard deviations of the mean (σ/). The red lines exhibit the stratifications of the mean UD, while the blue lines correspond to the mean nearby diffuse background (see main text for details). Negative LOS velocity values indicate upflows.