Koschmieder's law describes the relationship between visibility and the atmospheric extinction coefficient. This law states that visibility is inversely proportional to the extinction coefficient of the air. In other words, as the amount of particles and molecules in the atmosphere that scatter and absorb light increases, visibility decreases.
The law is based on the relationship:
whereby the visibility is and is the atmospheric extinction coefficient. This formula implies that a higher extinction coefficient, which indicates more particles in the air, results in a shorter visibility distance.
Although Koschmieder's law has been used for almost a century, its applicability is limited to specific circumstances. Recent studies have shown that the model is particularly suitable for situations where objects are observed at large distances (several tens of kilometers). At shorter distances, for example, several hundred meters, and for objects that occupy a larger angle in the field of view, the model is less accurate. Moreover, the law makes no distinction between detecting an object and clearly identifying it; the model is primarily applicable to the latter.
In practice, Koschmieder's law is often used to estimate meteorological visibility based on measurements of the atmospheric extinction coefficient. However, it is important to consider the model's limitations, especially under varying atmospheric conditions and at different observation distances.