Clouds are one of Earth’s most intriguing marvels. Not only do they play a major part in weather changes (mainly precipitation), but they serve a variety of other purposes. If you’ve ever wondered why clouds don’t stay still in the sky or how fast they travel, then this article is for you.
We’re going to dive deep into why clouds move and how quickly they do so, depending on the wind. So, read on to learn more!
Do Clouds Really Move?
Are clouds actually moving? The short answer? No. And while that fact may boggle your mind, it’s the Earth’s spin that creates this effect.
This spin is powerful, yet we don’t see or feel it at all. Why? Gravity. As you sit reading this, the Earth is spinning at a whopping 1600 kph (for those living near the equator, speeds slow a bit as you head toward the poles). And because of that gravitational pull, you don’t feel a thing.
But you can feel the wind, which is the result of the Earth’s spin. Thus, what pushes the clouds around in the sky, regardless of altitude. Clouds typically move in the direction the wind is blowing.
Yet, that isn’t always the case. Wind direction may differ at higher altitudes. This explains why you may feel the wind blowing from the East but see the clouds moving West.
How Clouds Move
The Role of The Sun
The sun (solar radiation) is largely responsible for the movement of air and water around our planet. This happens through the science of convection. The sun’s heat energy (especially infrared rays) transfers to warm and humid air masses, causing them to become less dense and rise. As a result, the cooler, more dense air is pushed down until it is heated and rises (convection).
The Role of Mountains (Topography)
The topography is another factor to consider when analyzing the movement of warm and humid air masses. Though related to convection, orographic lifting refers to air masses that are driven up and over mountains, rising and cooling as a result.
But what happens when two moving air masses meet? Well, that depends on the temperature of each mass. If the air mass is cooler (denser) it will hoist its warmer, less dense, counterpart further into the atmosphere.
In winter, when we experience fair and stable weather conditions, we may also experience thermal inversion. In this instance, the warmer air mass, which rises with altitude, traps the cooler air mass below. If the dew point is reached, thin layers of clouds will form a visible boundary between the two masses.
How Fast Do Clouds Travel?
As previously explained, it is wind currents in the atmosphere that make clouds appear as if they are the ones doing the moving. Removing these wind currents could mean no weather. The cooler temperatures of the wind allow clouds to condense and create precipitation.
Heftier, denser clouds (those packed with moisture and ice crystals) remain steadfast in the sky. These fluffy, opaque clouds will withstand high wind speeds. Less dense, wispier clouds are no match for the wind and will splinter.
How fast clouds can travel depends on where they originated. This determines how many miles they can travel in a day.
Some clouds can form as low as 5,000 feet while others, like cirrus clouds, form at more than 30,000 feet, meaning altitude plays a large role in their creation.
Wind simply doesn’t travel at the same speed throughout the different layers of the atmosphere.
Near the Earth’s surface, where there is more drag, winds are lighter and weaker. Winds higher in altitude are stronger and help to determine weather patterns.
The wind moves like a river in the sky. This is known as the jet stream and it is largely responsible for our weather and climate.
Horizontal vs. Vertical Movement
The very rising of a warm, humid air mass cooling and condensing as it ascends in the atmosphere is the catalyst for cloud creation.
Water droplets within the air mass constrict and become dense. The weight of the water droplets cannot be held and precipitation falls unless winds get to the cloud-first. Losing moisture causes the cloud to dissolve into the warmer air closer to the Earth, which evaporates any remaining moisture and erases the cloud altogether.
Upper-level winds, like the jet stream, guide the horizontal movement of clouds. Cirrus clouds typically indicate this wind direction. Warm and cold fronts also affect cloud movement as they are defined by the movement of the air masses behind them.
During a cold front, cold air invades and replaces a warm air mass in a given area. The opposite happens in a warm front. The movement of these masses generates wind that affects cloud movement, not just horizontally, but vertically as well.
So, as you can see, clouds don’t actually “move”. Not on their own at least. What you’re looking at is actually water vapor being condensed at a specific altitude while, simultaneously, the wind is moving this water vapor.