Cumulus (Cu)

A cloud genus that, together with Cumulonimbus, forms part of the vertically-developed clouds. It is a cloud that grows in isolation and is made up of a set of rounded forms, forming a dense cloud with usually well-defined outlines. The smallest cumulus (Cuhumilis) are entirely white and are colloquially known as fair-weather cumulus or cotton clouds. The medium-sized ones (Cumediocris) and particularly the large ones (Cucongestus) present a dark gray color at their base, due to the large amount of hydrometeors they hold within, as these elements form a natural screen that obstructs the passage of sunlight. That relative darkness of the base contrasts with the bright white displayed by the rest of the cloud when directly illuminated by the sun. The upper part takes the shape of a cauliflower. The vertical growth of a cumulus is dictated by convection, and it can present highly variable heights and sizes. Its base is located below 2000 m of altitude, and it can grow upward to 6000 m (at mid-latitudes). Inside the cumulus, rising air currents dominate, although in the largest ones they coexist with downdrafts associated with precipitation. The Latin word Cumulus means heap or pile, which well describes the piling up of the globular forms making up this convective cloud. Although that is its most common appearance, at times it appears torn, into shreds, which constitutes the species fractus.