Which PIREP involves reporting icing conditions?

The option describing moderate or greater icing is the correct choice because PIREPs, or Pilot Reports, specifically aim to provide crucial, real-time information regarding in-flight conditions, including weather phenomena. When pilots encounter icing, which can significantly affect aircraft performance and safety, it is vital to report its severity to help other pilots and air traffic controllers make informed decisions.

Moderate or greater icing conditions represent a significant hazard, as they can impact an aircraft's control, increase weight, and affect aerodynamic performance. As such, pilots are trained to observe and report these conditions, facilitating a wider understanding of potential hazards for all aircraft operating in the vicinity.

In contrast, the other options do not pertain to reporting icing conditions. Visual approach conditions relate to a pilot's ability to visually navigate towards the runway. Variable visibility is concerned with changes in how well pilots can see, which does not directly deal with icing. Wind direction changes, while crucial for flight operations and safety, are again unrelated to the issue of icing.