Also called polar stratospheric clouds or mother of pearl clouds, nacreous clouds are mostly visible within two hours after sunset or before dawn. They blaze unbelievably bright with vivid, iridescent colors. These clouds are rare and occur in the polar stratosphere at altitudes of 15,000–25,000 meters.They are so bright because at those heights, they are still sunlit.
Although incredibly beautiful, they have a negative impact on our atmosphere. They create ozone holes by supporting chemical reactions that produce active chlorine which catalyzes ozone destruction.
Space Shuttle Endeavour being ferried by NASA’s Shuttle Carrier Aircraft as it departs KSC. NASA pilots Jeff Moultrie and Bill Rieke are at the controls of the Shuttle Carrier Aircraft. Photo taken by NASA photographer Robert Markowitz in the backseat of a NASA T-38 chase plane with NASA pilot Greg C. Johnson at the controls.
Photo Date: September 19, 2012. Location: Kennedy Space Center, Florida. Photographer: Robert Markowitz
This photo was taken as the rain clouds began to build. Just as the sun was to set, it shone perfectly through the cloud, creating the “keyhole to heaven”. The Angel reflection around the outside of the cloud/light formation made this photo very unique.
Trapped beneath a warm air layer and directed by a cold northwesterly wind, fluffy cumulus clouds line up in bands called ‘cloud streets’ in an image captured Nov. 13 by NASA’s Terra satellite.
The visible light image by the satellite’s Moderate Resolution Imaging Spectroradiometer (MODIS) shows skinny, northwest-oriented clouds filling Hudson Bay in northeastern Canada.
Cloud streets — long parallel bands of cumulus clouds — form when cold air blows over warmer waters, while warmer air called an inversion layer rests on top of both, according to NASA’s Earth Observatory.
When heat and moisture from the comparatively warm water rise through the cold air above, the rising thermals hit the inversion layer, which acts like a lid. The thermals roll over and loop back on themselves, creating parallel cylinders of rotating air. As this happens, the moisture in the warm air cools and condenses into flat-bottomed, fluffy-topped cumulus clouds that line up parallel to the prevailing wind.
At the Exploratorium exhibit Icy Bodies, thin shavings of dry ice, warmed by the water they are floating in, emit cold jets of carbon dioxide gas. As the jets of gas shoot out, they spin the dry ice in a spiral pattern. As water vapor in the nearby air condenses into clouds, the pattern is revealed.
“During my first night in Fairbanks, Alaska in February 2012, the clouds broke a bit to reveal some auroral activity in the northern sky. The relatively low clouds are being lit by the reddish-orange light of Fairbanks.” — Dennis Mammana
The volcanoes of the South Sandwich Islands, located in the South Atlantic, have a notable effect on cloud formation in this satellite photo. Visokoi Island, on the right, sheds a wake of large vortices that distort the cloud layer above it. On the left, Zavodovski Island’s volcano does the same, with the added effect of low-level volcanic emissions, which include aerosols. These tiny particles provide a nucleus around which water droplets form, causing an marked increase in cloud formation visible in the bright tail streaming off the island. (Photo credit: NASA, via Earth Observatory)
“Cumulonimbus Cloud over Africa is featured in this image photographed by an Expedition 16 crewmember on the International Space Station. Deemed by many meteorologists as one of the most impressive of cloud formations, cumulonimbus (from the Latin for “puffy” and “dark”) clouds form due to vigorous convection of warm and moist unstable air. 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. This type of convection is common in tropical latitudes year-round and during the summer season at higher latitudes. 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 (right). 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. The view direction is at an angle from the vertical, rather than straight “down” towards the Earth’s surface. The image, photographed while the International Space Station was passing over western Africa near the Senegal-Mali border, shows a fully-formed anvil cloud with numerous smaller cumulonimbus towers rising near it. The high energetics of these storm systems typically make them hazardous due to associated heavy precipitation, lightning, high wind speeds and possible tornadoes.”
These ghostly wisps are called noctilucent clouds. They are perhaps the most rarely viewed cloud formation, only visible on Earth from higher latitudes after the Sun has dipped below the horizon, illuminating them from below. They are also the highest atmospheric clouds, at altitudes of nearly 50 miles above the Earth.
The origin of these “night-shining” clouds is debated, as they weren’t seen until after the Industrial Revolution. This jaw-dropping photo was captured from the International Space Station on June 13.