Refraction near the horizon-an empirical approach, Part 3: variability reduction of astronomical and terrestrial refractions at low positive and negative altitudes.

Near the horizon, atmospheric refraction depends primarily on the local vertical temperature gradient. Within the lowest ∼100m of the atmosphere, this gradient is nonlinear, typically following a log-linear profile over some height. I introduce a method for converting astronomical refractions between different temperature gradient profiles by scaling them using the ratio of corresponding refraction estimators. I demonstrate how to derive estimators to calculate both astronomical and terrestrial refractions as a function of altitude and the log-linear temperature gradients. These findings improve prediction accuracy in highly dynamic boundary layers, and also when analyzing atmospheric extinction or signal delay near the horizon.