Phénomènes de réfraction atmosphérique terrestre

Abstract

This article presents, almost without any analytical analysis, an orderly and illustrated presentation of the atmospheric—or terrestrial—refraction effects, i.e., affecting the vision of the apparent shape and position of objects located in the atmosphere, contrary to the case of astronomical refraction. The adopted classification, which is non-exhaustive as there are still mysterious atypical cases, is mostly based on the shape of the transfer curves and on the value of the refraction coefficient κ. Beginning with mirages, i.e. when an inverted image is formed, four main types are identified: inferior, superior, Nachspiegelung and mock-mirage, multiple mirage. Then comes the special case of Fata Morgana: their archetypal form is a transition case whose physical cause remains imperfectly understood, and their real forms are more complex and varied, although often linked to superior mirages. Finally remain the unusual cases without inverted image: stooping/stretching, sinking, looming, and finally hillingar effect—corresponding to a strong looming (κ>1) and giving the illusion that a flat horizontal surface, e.g., the sea, is concave.