What is the criterion for light ice pellets?

The criterion for light ice pellets focuses on the presence of scattered pellets that do not cover an exposed surface. This definition aligns with the characteristics of light ice pellets, which are typically small and may occasionally fall without significantly accumulating on surfaces, thereby maintaining visibility.

Since "scattered pellets" suggests a limited amount of precipitation that features ice pellets, it captures the essence of the light category, emphasizing the dispersed nature of the precipitation rather than creating a blanket effect on the ground. This is important for pilots and meteorologists, as the presence of ice pellets can impact conditions without obscuring visibility or completely covering surfaces.

The other options reference conditions that are either too general or suggest heavier accumulation, which does not meet the specific definition of light ice pellets. For instance, covering the ground would imply a more significant accumulation than what is classified as "light," while piles affecting visibility would denote a greater density that again contradicts the light classification. Additionally, average size does not directly relate to the criterion necessary to define the light nature of the ice pellets, as size alone does not inform about their distribution or impact on the surface.