This large and unusual cloud formation was captured one July morning over western Australia. Stretching over 1,000 kilometers, the clouds have interesting features at both the large and small scale. The small-scale ripples within the clouds are gravity waves triggered by the terrain below. The larger, arced features are tougher to explain, though they may also be related to gravity waves and terrain, just on a much larger scale. They also resemble fallstreak clouds where supercooled droplets evaporate from the inside of the cloud out. (Image credit: W. Liang; via NASA Earth Observatory)
Tag: satellite image
Predicting Landslides
Landslides can cause catastrophic damage, but historically it’s been difficult to monitor susceptible slopes and predict when they’ll fail. But a recent study looking at the 2017 Mud Creek landslide in California shows that new methods could provide a heads up.
The researchers used satellite data from the months preceding the landslide to study how areas on the slope moved relative to one another. Within their survey region, they found sub-regions where ground locations largely moved together. These sub-regions, called communities in the researchers’ parlance, were remarkably persistent, showing little variation over long periods. But 56 days before the landslide, the researchers saw a sudden change between the communities on the slope. They believe their methodology could help identify slopes in danger of imminent slides.
So far, though, they’ve only applied this method to the Mud Creek landslide. It’s a promising start, but they’ll need to show that the technique works for other slides as well. If so, it will be a major step forward in landslide prediction. (Image credit: USGS; research credit: V. Desai et al.; via APS Physics)
Atlantic Blooms
In April 2023, swirls of green and turquoise burst into vivid color in the Atlantic. Much of the color comes from a phytoplankton bloom. Although phytoplankton are individually microscopic, they form eddies a hundred kilometers across that are visible from space. In detailed images like the one above (available here in full resolution) these swirls have amazing turbulent details. Some of the brightest sections almost look like a field of sea ice! (Image credit: L. Dauphin; via NASA Earth Observatory)
Anabranching Riverways
The Diamantina River in Australia is dry for much of the year. But seasonal rains flood its riverbeds and provoke a bloom of vegetation along its banks. This false-color satellite image shows the river in April 2023; land appears pale and reddish, the river and its sediment blue, and vegetation a bright green. The Diamantina is an anabranching river; rather than the typical meandering paths of a delta, anabranching rivers have semi-permanent paths hemmed in by vegetation-stabilized islands. Look closely, though, and you’ll still see smaller delta-like features known as floodouts dotting some of the islands. (Image credit: A. Nussbaum; via NASA Earth Observatory)
This close-up shows details like miniature deltas (floodouts) and wind-formed dunes. 
Swirls Over the Canaries
Rocky, isolated islands disturb the atmosphere, sending air swirling off one side of the island and then the other. The effects are not always visible to the naked eye, but, as they do here, they can show up in satellite imagery as whirling von Karman vortex streets. The eddies of this image are due to the Canary Islands, and if you follow the line of swirls backward, you’ll find their originating islands. Note that the cloudy swirls don’t appear immediately behind the islands. That’s because there wasn’t enough moisture in the air for clouds to condense yet; the same swirls that you see in the downstream clouds exist in the clear air closer to the islands. (Image credit: A. Nussbaum; via NASA Earth Observatory)
Wave Clouds From Space
An astronaut snapped this image of wave clouds formed around the Crozet Islands, which lie between South Africa and Antarctica. Clouds like these form when warm, moist air gets pushed up and over a mountain. As it rises, the air cools and its pressure decreases, causing condensation. Pushed out of equilibrium, gravity then pulls the air back downward in the wake of the mountain. That warms the air, causing evaporation. Like a mass bouncing on a spring, the air continues to yo-yo up and down, forming cloudy stripes and clear ones until the energy from its mountain climb is spent. (Image credit: NASA; via NASA Earth Observatory)
A Sea of Pollen
Fellow allergy sufferers, beware! This false-color satellite image of the Baltic Sea shows massive slicks made up of pine pollen. I don’t know about you, but the mere thought of enough pollen that it’s visible from space makes me want to double — triple?! — my antihistamines. The swirling patterns in the pollen come from wind-driven currents and waves moving the pollen on the surface of the water.
It took some sleuthing for scientists to identify these slicks as pollen rather than bacteria or plankton. But by combining experimental results, ground-based observations, and satellite image processing, scientists discovered that the pine pollen has a particular spectral signature. Using that, the team could trawl through older satellite imagery and locate pine pollen in previous seasons. They identified pine pollen slicks in 14 of the last 20 springs. The size of the slicks is growing over time, too, consistent with other observations of longer pollinating seasons. (Image credit: L. Dauphin; via NASA Earth Observatory)
Stirring Up Sediment
In early February, Tropical Cyclone Gabrielle passed over the Bellona Plateau in the Coral Sea, stirring up sediment from the shallow reefs there. Once the storm cleared, large swirls of carbonate sediment mixed into the deeper waters around the plateau. As the sediment sinks to depths of kilometers, it will dissolve into the deep ocean waters, eventually getting captured as part of sedimentary rocks. This is a critical step in the ocean’s carbon capture cycle.
Unfortunately, climate change is disrupting the ocean’s ability to capture carbon. An excess of carbon dioxide acidifies ocean waters, making it harder for creatures like corals and crabs to incorporate carbon into their bodies. That reduces sources for carbonate sediments like those seen here. Changes in ocean chemistry also affect where and how much carbonate can get dissolved. In short, ocean carbon capture has been an important process for Earth’s carbon cycle in the past, but the process is a slow one, and human activity has overloaded the ocean’s system in ways we don’t fully understand. (Image credit: A. Nussbaum; via NASA Earth Observatory)
Finding the Red in the Red Tide
Blooms of the algae Karenia brevis — known as a red tide — bring havoc to Gulf Coast shores. The algae can kill fish and other marine life, and it causes skin irritation and even respiratory problems for humans. But in spite of the moniker, these algae can be hard to spot; they can add a green, brown, red, or black hue to the water.
The false-color image above uses a new image processing technique that reveals the bloom. Using satellite images taken over multiple days, scientists can track and study the red tide in unprecedented detail. The new technique will be a boon to those trying to monitor and understand red tides. (Image credit: Y. Yao/USF/Planet Labs/L. Dauphin; via NASA Earth Observatory)
Cellular Clouds
Though tough to make out from the surface, our oceans are often covered by cell-shaped clouds stretching thousands of kilometers. This satellite image shows off two such types of marine stratocumulus cloud. Open-celled clouds appear as thin wisps of vapor around an empty middle; in these clouds, cool air sinks through the center while warm air rises along the edges. Open-celled clouds are good rain producers.
On the flip side, closed-cell clouds have a vapor-filled center and breaks in the cloud cover along each cell’s edge. These clouds don’t produce much rain, but they do lift warm, moist air through their middles and let cool air sink along their edges. Closed-cell clouds tend to last much longer than their open-celled counterparts; they can stick around for half a day, whereas open-celled clouds break up in only a couple hours. (Image credit: J. Stevens; via NASA Earth Observatory)
