The clouds remain suspended in the air because the water droplets or ice crystals that compose them are held in equilibrium by aerological forces such as gravity, atmospheric pressure, and vertical air movements.
Clouds are primarily made up of tiny water droplets or fine ice crystals. These microscopic particles come from the condensation of water vapor present in the air. They are so small, just a few microns, that they remain suspended due to the resistance of the air. For these droplets to exist, they generally need to form around tiny solid particles in suspension, called condensation nuclei. These tiny elements can be dust, pollen, or even volcanic ash. The density and size of the droplets directly influence the hue, shape, and appearance of the clouds you observe from the ground. Some often appear very solid, but they are actually composed mainly of air, with very little water in a large volume.
Clouds form primarily due to moist air rising and cooling at high altitudes. The higher the air rises, the lower its temperature drops, causing water vapor to transform into fine droplets of liquid water: this is called condensation. Conversely, if the air temperature rises or becomes drier, these tiny droplets revert to vapor, a phenomenon known as evaporation. In clouds, condensation and evaporation occur continuously and simultaneously. This balance between droplets appearing and disappearing allows clouds to remain visible longer without necessarily falling as rain immediately.
Clouds stay in the air primarily thanks to updrafts, which are currents of warm air that rise from the ground to the top of the atmosphere. These currents form when the sun heats the ground, causing the lighter warm air to rise, taking moisture with it. If these updrafts are strong enough, they counteract the weight of the tiny water droplets or ice crystals that make up the cloud. It's a whole battle against gravity: while gravity pulls the particles downward, the upward movement of the warm air supports and keeps them aloft. The very small size of the droplets also helps in their suspension, as their falling speed is extremely slow, making it easier for them to stay suspended. In other words, as long as the particles are small enough, and the updrafts are active and powerful, clouds remain peacefully suspended above our heads.
In every cloud, there are many tiny particles called aerosols, such as dust, pollen, or even bits of pollution. These particles, nicknamed condensation nuclei, act as attachment points around which suspended water gathers to form many mini droplets. The more particles there are, the more fine droplets there will be, allowing the cloud to remain suspended for a long time without falling. The size and number of these nucleation nuclei directly influence the cloud's lifespan, density, and even color. Without these tiny particles, the vapor would remain in a gaseous state for a longer time, making the formation of clouds much slower or less abundant.
The clouds remain suspended due to a delicate balance between their weight, caused by water droplets, and the upward thrust of rising air currents. This is not a static state, but a dynamic phenomenon where droplets grow through condensation while others shrink through evaporation. These tiny droplets fall slowly, but constant upward air movements prevent them from falling completely. This ongoing play of opposing forces allows clouds to float for hours, or even an entire day, without releasing rain. As soon as this balance is disrupted, often when the droplets become too heavy or when the upward currents weaken, down comes the rain!
Thunderstorm clouds, or cumulonimbus, can reach impressive heights of up to 20 kilometers. These gigantic clouds can cause extreme weather phenomena such as torrential rain, lightning, and even tornadoes.
Some clouds, like cirrus, which you often see high in the sky, are mainly composed of tiny ice crystals rather than liquid water droplets.
Fog is nothing more than a cloud located at low altitude, close to or in direct contact with the Earth's surface. It forms when the ambient humidity condenses into tiny water droplets in the air.
A medium-sized cloud can weigh as much as several hundred tons or even more. Yet, despite this impressive weight, they remain suspended due to the distribution of the weight of small droplets over a very large volume of air and the upward currents.
Droplets form when the water vapor present in warm, humid air cools and condenses around small particles called condensation nuclei, which are typically dust or mineral elements suspended in the atmosphere.
Fog is simply a particular type of cloud that is located at ground level. It results from the same condensation phenomenon as clouds at higher altitudes, but occurs when condensation takes place near the ground, thereby limiting visibility.
Airplanes can fly through clouds because they are made up of tiny water droplets or ice crystals suspended in the air, which are easily displaced. The rapid passage of an airplane barely affects the dynamic balance and overall structure of the cloud.
The ability of a cloud to produce precipitation primarily depends on its size, the density of water droplets, and its internal dynamics (updrafts and downdrafts). When the droplets reach a critical size, they become too heavy to remain suspended and fall as rain.
The color of clouds mainly depends on their thickness and density. White clouds reflect sunlight well, while thicker or denser clouds absorb and block more light, making them appear gray or even dark.
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