FYFD

Tag: satellite image

  • Saharan Dust

    Saharan Dust

    In late January, dust from the Sahara blew westward toward the Cabo Verde archipelago before turning northward toward Europe. During winter and spring, Saharan dust tends to stay at lower altitudes, where it can be carried by the northeast trade winds. In contrast, from late spring to early fall, dust rises higher, carried westward by the Saharan Air Layer; there, the dust can help suppress both the formation and intensity of the Atlantic’s hurricanes.

    On the left side of the image scant clouds trace von Karman vortex streets behind the archipelago, marking the atmospheric disruption caused by the rocky islands. (Image credit: L. Dauphin; via NASA Earth Observatory)

  • Swirls Off South Australia

    Swirls Off South Australia

    Summer winds along Australia’s Bonney Coast push coastal waters offshore, triggering the upwelling of colder waters from depths below 300 meters. These cold waters from the deep are nutrient-rich, thanks to all the decomposition that happens along the ocean floor. The infusion of nutrients triggers an explosion of life, visible here in the form of a green phytoplankton bloom along the shelf break. In turn, the phytoplankton attract fish and blue whales. Even great white sharks are drawn to the cornucopia. (Image credit: W. Liang; via NASA Earth Observatory)

  • Seeding Clouds

    Seeding Clouds

    In the remote South Atlantic, north of the Antarctic Circle, sit the volcanic Zavodovski and Visokoi islands. Though only roughly 500 and 1000 meters tall, respectively, each island disrupts the atmosphere nearby, often generating cloudy wakes. In today’s pair of images, the northerly Zavodovski has a particularly bright cloud wake, thanks to sulfate aerosols degassing from its volcano, Mount Curry. Though it’s hard to pick out the effect in the natural-color image above, the false-color version below shows the bright wake clearly. The filtering on this image turns snow and ice — like that on Visokoi’s peak — red and makes the water vapor of clouds white. The sulfates from Mount Curry act as nucleii for water droplets, forming many small, reflective drops that stand out against the rest of the sky. (Image credit: W. Liang; via NASA Earth Observatory)

    This false-color satellite image highlights the volcanic seeding by filtering snow and ice as red and water vapor in clouds as white.
    This false-color satellite image highlights the volcanic seeding by filtering snow and ice as red and water vapor in clouds as white.
  • Upwelling at Cabo Frio

    Upwelling at Cabo Frio

    The shores of the Brazilian state of Rio de Janeiro boast turquoise waters, white sands, and green lagoons, but European explorers discovered the waters around one promontory were unusually cold, leading to the name Cabo Frio. The chilly waters can be 8 degrees Celsius cooler than nearby surface temperatures, thanks to cold water upwelling near the coast. The upwelling is wind-driven; the dominant northeasterly winds push water out to sea, allowing colder waters to rise from the deep. (Image credit: L. Dauphin; via NASA Earth Observatory)

    A map of sea surface temperatures near Cabo Frio in Brazil.
    A map of sea surface temperatures near Cabo Frio in Brazil.
  • Fire in Ice

    Fire in Ice

    This false-color satellite image of Malaspina Glacier (Sít’ Tlein) is a riot of color. Composed of coastal/aerosol, near infrared, and shortwave infrared bands from Landsat 9, the colors highlight features otherwise hard to identify. Watery features appear in reds, oranges, and yellows; vegetation is green and rock appears in blue. The glacier covers more than 4000 square kilometers, an area larger than the state of Rhode Island. The dark lines atop the glacier are moraines, where rock, soil, and other debris has been scraped up along the glacier’s edge. Over time, changes in the glacier’s velocity cause the moraines to fold and shear, creating the zigzag pattern seen here. (Image credit: W. Liang; via NASA Earth Observatory)

  • Swirling Sea Ice

    Swirling Sea Ice

    The Sea of Okhotsk is the northern hemisphere’s southernmost sea that seasonally freezes. Caught between the Siberian coast and the Kamchatka Peninsula, cold air from Siberia helps freeze water kept at lower salinity due to freshwater run-off. This image, taken in May 2023, shows free-floating sea ice forming spirals driven by wind and waves. Small islands off the eastern coast (right side in image) are likely responsible for the swirling eddies seen there. Like phytoplankton blooms and sediment swirls in warmer seasons, the sea ice acts as a tracer to reveal flow. (Image credit: W. Liang; via NASA Earth Observatory)

  • An August Arc

    An August Arc

    In summer, the fjords of Greenland are littered with ice, but in August 2023, satellites caught an odd interloper. See the thin white arc spanning the fjord in the photo above? Scientists suspect this ephemeral feature was a wave caused by a large iceberg calving off the glacier on the right. When large chunks of ice fall into the water, they can cause distinctive waves that travel out from the point of impact.

    Another possible mechanism is an underwater plume. In Greenland’s fjords, such plumes are sometimes formed from freshwater melting below the glacier. When that water rises to the surface, it can push ice. (Image credit: W. Liang; via NASA Earth Observatory)

  • Field of Dunes

    Field of Dunes

    Barchan dunes collide in this astronaut image of Brazil’s southern coastline. Barchan (pronounced “bar-kahn”) dunes are crescent-shaped; their tips point downwind into their direction of travel. When many barchan dunes overlap, they coalesce into a dune field like the one seen here. A dune’s speed depends on many factors, including the wind speed, dune size, and its proximity to other dunes. In experiments, dunes have even chased one another and changed speeds to avoid collision. (Image credit: NASA; via NASA Earth Observatory)

  • Complex Dunes

    Complex Dunes

    Sometimes landscapes have a beauty that’s hard to see from the ground. This astronaut’s photo shows a dune field in the sand seas of Saudi Arabia. Vast linear dunes line up along the direction of prevailing winds. Atop these dunes are more complex formations, star dunes, that are built up in the wake of changing winds. Built from three or more intersecting arms, the star dunes are steeper than the linear dunes they sit atop. Such complex dune fields — with multiple types of dunes — form in areas with especially abundant sands. (Image credit: NASA; via NASA Earth Observatory)

  • Clouds Down Under

    Clouds Down Under

    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)