What term describes when visibility is not the same around the horizon circle?

The term that describes when visibility is not the same around the horizon circle is "non-uniform." This indicates that there are variations in visibility from one point to another along the horizon, which can be influenced by factors such as weather conditions, topography, or the presence of obstructions. When visibility is non-uniform, pilots and meteorologists acknowledge that specific areas may have significantly clearer or more obstructed views than others, which is crucial for flight planning and safety assessments.

In contrast, terms like "uniform" or "consistent" imply an even distribution of visibility, where the conditions remain the same around the entire horizon, which does not accurately reflect the scenario. The term "variable" could be misleading because it might suggest that visibility changes at different times or under different conditions rather than describing the consistent differences from one point to another around the horizon circle. Thus, "non-uniform" is the most precise term to describe this situation.