Stratus doesn’t have the identity crisis of stratocumulus. While stratocumulus has features of both layer and cumulus (heap) clouds, but is really neither, stratus is a layer cloud all the way. Forming in calm, moist air, stratus has virtually no definition to it. It is so uniform and featureless that weather observers have difficulty determining the height of its base by eye alone. They have to release a balloon and, knowing its ascent rate, time its disappearance into the cloud. Or they could use an instrument such as lidar.Stratus cloud, if it were touching the ground, would be fog. In fact, stratus often forms as a result of a fog lifting.