What is an obscuration in meteorology?

In meteorology, obscuration refers specifically to conditions that reduce visibility, typically due to particles in the atmosphere such as smoke, haze, or fog. When visibility is impaired by these elements, it can pose significant safety risks for aviation and other outdoor activities. This definition encompasses various scenarios where the atmosphere's clarity is compromised, leading to challenges in seeing distant objects or navigating.

The other options, while related to visibility issues, do not accurately capture the broader definition of obscuration. A scenario where the sky is obscured by clouds may affect visibility, but it is not classified under the same conditions as smoke, haze, or fog, which fundamentally contribute to obscuration in meteorological terms. The mention of nighttime visibility addresses a different aspect of atmospheric conditions that might affect operations but does not directly pertain to obscuration as defined in this context. Lastly, thunderstorms are specific weather phenomena that can lead to obscuration but do not represent the general definition of the term itself.