I and pinkie pie are studing and practicing clouds.
In Latin, clouds are often considered nimbus.
Based off observation, I'd say these are about med-level clouds.
Mid-level clouds typically appear between 6,500 to 20,000 feet (2,000 to 6,000 meters). Because of their lower altitudes, they are composed primarily of water droplets, however, they can also be composed of ice crystals when temperatures are cold enough.
When reflected by the sun, These clouds appear to have a light titanium white mixed with the horizon ,Which shows a 3d texture when Directed to light, and shading away.