Cloud Towers
In a view from high altitude, height can be a difficult thing to gauge. The
highest of clouds can appear to sit on a flat plane, as if they were at the same
elevation as the ocean or land surface. In this image, however, texture, shape
and shadows lend definition to mushrooming thunderheads over the Indonesian
island of Flores. The Moderate Resolution Imaging Spectroradiometer (MODIS) on
NASA’s Aqua satellite acquired this image on the afternoon of Dec. 2, 2013.
The towering clouds are so well defined that it is easy to visualize the
rapidly rising air that is fueling them. “This looks like a classic example of
island convection that is enhanced by topography,” says NASA scientist Joseph
Munchak.
During the day, sunlight heats the land more quickly than it heats the ocean.
The warm air over land rises, creating an area of low pressure that pulls in
cool air from the ocean. The result is a sea breeze. On this Indonesia island,
the sea breeze from the Flores Sea on the north blows inland and clashes with
the sea breeze blowing inland from the Savu Sea in the south. When the two
breezes meet in the center of Flores, they push the air up. The rising air cools
and condenses into a line of clouds.
Sea breeze convection is not the only force at work here. On Flores, cloud
formation has help from the shape of the land. A line of tall volcanoes runs
down the spine of the island, and their steep slopes also force air to rise. So,
moist ocean air blows inland, hits the mountains and volcanoes and rises with
the slope. Above the mountains, the rising air meets the rising sea breeze from
the other side, and the upward motion is reinforced.
The combination of the two forces pushes air high into the atmosphere,
resulting in large towering clouds of the sort that usually produce
thunderstorms. In fact, a weather station on Flores reported rain and
thunderstorms on December 2. This type of convection is strongest in the early
afternoon, says Munchak, just about the time when Aqua MODIS acquired the image.
The clouds were just beginning to form when Terra MODIS passed over earlier in
the day.
Image Credit: NASA/Jeff Schmaltz, LANCE/EOSDIS MODIS Rapid Response Team,
NASA GSFC
Caption: Holli Riebeek
Caption: Holli Riebeek
NASA
Guillermo Gonzalo Sánchez Achutegui
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