Which factor is essential in defining total obscuration in weather observations?

Total obscuration in weather observations refers to a situation where visibility is significantly hindered, preventing observers from seeing any landmarks or features beyond a certain range. The defining factor for total obscuration is the presence of cloud cover. When cloud cover is extensive or thick enough, it can completely block out the sky, leading to limited visibility below the clouds. This is particularly true in aviation, where understanding cloud cover is vital for safe operations and navigation.

While factors such as surface-based fog, visibility nuances, and sky condition elevation can affect visibility and contribute to obscured conditions, they are not the primary defining elements for total obscuration. Cloud cover specifically indicates the extent to which the sky is obscured, making it the essential factor in understanding total obscuration within weather reporting contexts.