There are many other cloud variations that form by clouds mixing up or dispersed by wind action. Others are rare and can be seen only at nigh. Here are a few more that do not fit within the traditional ones we learned.
Have you ever seen an aircraft flying high in the sky with a trail of cloud following it? Those are contrails and they are a type of cloud too. The exhaust of airplanes produce emissions such as *carbon dioxide, water vapor, nitrogen oxides (NOx), carbon monoxide, hydrocarbons such as methane, sulfates (SOx), and soot and metal particles.
Water vapor, both from the airplane and in the air, condense around these tiny particles, forming a trail of clouds. Some contrails last only for a short period of time whiles others last for days. Unlike other cloud types, contrails are human induced because they are caused directly by flying airplanes.
Fog is a cloud at the ground, and they usually disappear when the sun is up and begins to warm the land surface. The four kinds of fog include radiation fog, advection fog, evaporation fog, and upslope fog. After a warm, sunny day, the land surface is heated and the air over it warm with a bit of water vapour. In the night, as the temperatures fall, the surface heat radiates upwards, but as it meets cooler air above it, it is forced to condense. In industrial areas where the air has a lot more particulate matter, fog occurs more because the particles make it easier for the water droplets to form around it. As the sun comes up the next morning and the air warms up the fog gradually disappears.
This is an awesome looking cloud, resembling a flying saucer or a stack of pancakes. It is often formed close to a mountain peak when fast flowing wind if forced up and over it. If there is enough moisture at the mountain tops, the wind-waves cause the resulting clouds to take the shape of the wave.