Which type of cloud is associated with significant vertical currents at low levels?

The type of cloud associated with significant vertical currents at low levels is cumulus. Cumulus clouds form when warm, moist air rises due to convection, creating instability in the atmosphere. As this air rises, it cools and condenses, forming the characteristic puffy, white clouds we recognize as cumulus. The vertical currents within these clouds can lead to the development of stronger weather phenomena, including updrafts and downdrafts, especially when they grow larger and can develop into cumulonimbus clouds, which are associated with thunderstorms.

In contrast, stratus clouds are typically flat and layered and do not exhibit strong vertical development or significant vertical air currents. Nimbostratus clouds are continuous, thick clouds that often bring steady precipitation but lack the strong vertical growth seen in cumulus clouds. Altostratus clouds are mid-level clouds that also form in stable conditions, generally indicating an overcast sky, without the same degree of vertical motion as cumulus clouds. Thus, the key characteristic of cumulus clouds that pertains to this question is their formation process, which inherently involves notable vertical air currents at low levels.