An accurate model for propagation of infrared energy within the marine atmospheric surface layer remains an elusive goal. Within the first tens of meters of elevation above the sea surface there are substantial vertical gradients of mass and temperature. This has a strong effect on the prediction of extinction of the infrared signal. There exist models to enable the computation of the effects generated by these factors, but often these models contribute only extinction factors. The refractive propagation factor is proposed as a critical component of an accurate transmission model within the marine surface layer. The propagation factor is a multiplicative quantity that is derived entirely from the local refractive field and the geometry of the entire transmission system. A ray-trace model is used to compute the refractive magnification or minification. The ray-trace model also elucidates the importance of mirage images to account for all energy received at the sensor. I will present a comparison of the model with field data that contain episodes of anomalously large signal intensities. The core thesis of this paper is that the necessary final component in a complete model for near-sea-surface infrared transmission is the propagation factor induced by refractive effects.