This picture shows a lenticular cloud over the Tararua Range mountains, North Island, New Zealand. What's happening above those mountains? Several clouds are stacked up into one striking lenticular cloud. Normally, air moves much more horizontally than it does vertically. Sometimes, however, such as when wind comes off of a mountain or a hill, relatively strong vertical oscillations take place as the air stabilizes. The dry air at the top of an oscillation may be quite stratified in moisture content, and hence forms clouds at each layer where the air saturates with moisture. The result can be a lenticular cloud with a strongly layered appearance.
Credit and copyright: Chris Picking (Starry Night Skies Photography).
Have you ever seen six rainbows at once? They are not only rare to see—they are a puzzle to understand. The common rainbow is caused by sunlight being reflected by the backs of falling raindrops, while also being refracted at the air/water boundary. The sunlight in this picture is coming from behind the observer, and the rainbows are in the rainstorm.
The brightest rainbow is the primary rainbow. Above and to the left of the main rainbow is a secondary rainbow, caused by multiple internal reflections inside water droplets, with colors reversed. The intermediate rainbow is likely caused by sunlight that first reflected off the lake before striking the distant raindrops, which then reflect sunlight back toward the observer. The other three rainbows are reflections of the rainbows in the sky on the lake's surface. Kind of cheating to say there are six rainbows, but why argue with such a spectacular show? (NASA).
Sometimes we see two rainbows at once, what causes this? In a rainbow, a ray of sunlight enters and is reflected inside the raindrop. But not all of the energy of the ray escapes the raindrop after it is reflected once. A part of the ray is reflected again and travels along inside the drop to emerge from the drop. The rainbow we normally see is called the primary rainbow and is produced by one internal reflection; the secondary rainbow arises from two internal reflections and the rays exit the drop at an angle of 50 degrees rather than the 42 degrees for the red primary bow. Blue light emerges at an even larger angle of 53 degrees, this effect produces a secondary rainbow that has its colors reversed compared to the primary.
Cumulonimbus clouds over Africa can reach a height of 12 miles (20 kilometers). Drier air causes the anvil shape.
This picture shows cumulonimbus clouds over Africa photographed from the International Space Station. Cumulonimbus (from the Latin for "puffy" and "dark") clouds form due to vigorous movement of warm and moist unstable air. Rising air currents containing water vapor and varying layers of differing-temperature air in the upper atmosphere result in these dramatic cloud formations.
Here, surface air warmed by the sun-heated ground surface rises, and if sufficient atmospheric moisture is present, water droplets will condense as the air mass encounters cooler air at higher altitudes. The air mass itself also expands and cools as it rises due to decreasing atmospheric pressure, a process known as adiabatic cooling. As water in the rising air mass condenses and changes from a gaseous to a liquid state, it releases energy to its surroundings, further heating the surrounding air and leading to more convection and rising of the cloud mass to higher altitudes. This leads to the characteristic vertical "towers" associated with cumulonimbus clouds, an excellent example of which is visible in this image.
If enough moisture is present to condense and continue heating the cloud mass through several convective cycles, a tower can rise to altitudes of approximately 10 kilometers at high latitudes to 20 kilometers in the tropics -- before encountering a region of the atmosphere known as the tropopause. The tropopause is characterized by a strong temperature inversion where the atmosphere is dryer and no longer cools with altitude. This halts further vertical motion of the cloud mass, and causes flattening and spreading of the cloud tops into an anvil-shaped cloud as illustrated by this oblique photograph.
Evaporation - Early morning fog fills the valley floors in New Zealand
Clouds Overhead ... Clouds Underfoot
Yes, the fog you see in these valley floors in New Zealand is the same thing as clouds you see floating overhead in the sky. Clouds are formed when invisible water vapor in the atmosphere condenses out into visible water droplets. Condensation is highly dependent on the amount of water vapor in the air (relative humidity) and temperature (water condenses more readily in colder air). So, if the air at the land surface is sufficiently humid and cold condensation can occur, with the result being clouds you can literally walk on, or "through" might be a better term.
Summer thundershowers over Yellowstone Lake, Montana, USA.
This picture shows a local thunderstorm moving across Yellowstone Lake, Montana, USA. Likely this picture was taken in the summer, as that is when more localized storms occur. Other rainstorms are more "frontal" in nature, with large expanses of featureless and uniform nimbostratus types of clouds bringing precipitation over a large area. But often you see a landscape similar to the one in this picture, with rain falling in a localized area (and often moving right towards your picnic) from a relatively small cloud. The sheets of rain are easily seen. Often these storms are intense but brief.
Condensation: Contrails made by a high-flying airplanes, over Lake Jackson, Florida, USA
You've seen the cloud-like trails that high-flying airplanes leave behind and you probably know they are called contrails. Maybe you didn't know they were called that because they are actually condensation trails and, in fact, are not much different than natural clouds. If the exhaust from the airplane contains water vapor, and if the air is very cold (which it is at high altitudes), then the water vapor in the exhaust will condense out into what is essentially a cirrus cloud. As this picture shows, contrails start out as thin ribbons but with upper-atmosphere winds, they can dissipate and essentially form much larger sets of cirrus clouds.
Evaporation - Seawater evaporation ponds on the Isle of Rhé off the coast of France
In the modern world, people take salt for granted (and in fact, often consume too much salt in their diets). But in ancient times, salt was a very valuable commodity in many places. With no refrigeration to preserve food, people had to come up with ways of keeping meats, breads, and dairy products fresh over the many months when fresh food wasn't growing and wasn't available. Thousands of years ago it was found that salt could be used to preserve foodstocks over the winter months. For people living near the oceans or briny water bodies, evaporation ponds were, and still are, used to evaporate seawater, leaving solid salt deposits. No doubt that early Roman Empire salt ponds looked very similar to these in France.
By the way, the salt concentration of seawater is about 3.5 percent.
Evapotranspiration: Plants transpire water from their leaves
After a plastic bag is wrapped around part of a plant, the inside of the bag becomes misty with transpired water vapor. In this experiment performed at a school in China, students could notice the water buildup inside the plastic bag within an hour after it was tied around the plant.
Condensation: Clouds over Kiger Notch, Steen's Mountain, Washington, USA
This picture shows a common sight seen during fair-weather days where there are mountain and ridges in the landscape. Maybe you've wondered why big, puffy clouds seem to like to hang out near mountain ridges and above mountain peaks. The mountains are not putting out more humid air than other areas, but the process of condensation is taking place because of the mountains. In the United States, since weather moves generally west to east, this is more easily seen when moving air from the west hits higher terrain and is pushed up by the landscape as the air travels eastward.
Although you don't see the water vapor in the clear air approaching and moving upward and above the mountain ridge, vapor is present and the potential for clouds are present, too. As the air is pushed up by the landscape, the higher-altitude air is cooler than the moving air, so condensation occurs and clouds form. Often this is responsible for rain on the windward sides of mountain ranges, such as the Sierras in California, and much drier air on the leeward side of the mountains, as in Nevada.
Bubbles contain water and soap. In a bubble, there is a layer of water sandwiched between two layers of soap molecules. The water property surface tension holds the bubble together (at least for a while). Bubbles tend to form into sphere shapes because the laws of physics is trying to minimize the surface area of the bubble—and a sphere is the shape that has a minimum surface area.
If you go far enough out in space, for instance, onto the International Space Station, gravity becomes negligible, and the laws of physics act differently than here on Earth. This unique picture shows not only a water drop but also an air bubble inside of the water drop. Notice they both behave the same....according to the laws of physics in space. They both form spheres. This makes sense, as without gravity to tug downward, the forces governing the objects are all the same. So, the water drop (and air bubble) form themselves so they occupy a shape having the least amount of surface area, which is a sphere. On Earth, gravity distorts the shape, but not in space.
Consider what would happen on Earth: The air bubble, lighter than water, would race upward to burst through the surface of the droplet. In space, the air bubble doesn't rise because it is no lighter than the water around it—there's no buoyancy. The droplet doesn't fall from the leaf because there's no force to pull it off. It's stuck there by molecular adhesion.