What indicate a runway is considered 'dry' in current aviation standards?

A runway is considered 'dry' in current aviation standards when it can accommodate safe aircraft operations without the presence of significant water that could lead to hydroplaning or reduced friction. This definition acknowledges that specific treatments can allow a runway to maintain its dry status even if some water is present.

In particular, the use of grooved or porous friction surfaces can effectively channel water away from the runway surface, thus preventing the accumulation that would typically constitute a wet or slippery runway. This treatment enhances friction between the tires and the runway, which is critical for safe landing and takeoff.

The other options, while related to runway conditions, do not fully encompass the aviation standards for a runway to be classified as 'dry'. For instance, while it is important for a runway to be clear of standing water, this alone does not cover the broader criteria that allow for some water presence if mitigated by engineering practices like grooving or porous treatments. Similarly, being clear of snow and ice is essential for operational safety, but does not specifically define 'dry' in the context of water management.