February 25th, 2014 by Adam Voiland
February 5th, 2014 by Mike Carlowicz
Last week we shared an image of an 800-kilometer long bloom of marine protists off the coast of Brazil. In satellite imagery, the bloom appeared navy to black in color, even though the species—Myrionecta rubra—appears red when viewed close-up. The blooms tend to occur just below the water surface, so much red light that the protists reflect gets absorbed before it returns to the satellite. Here’s a look at the January bloom from a boat in the South Atlantic.
The photos were taken in the late afternoon on January 22, 2014. The boat was positioned at roughly 24° 08′ South and 45° 07′ West. The water temperature was 29°Celsius (84°Fahrenheit) and the depth was 70 meters (230 feet).
Thanks to Julio Cardoso, a boater and amateur scientist from Brazil who shared the photos with us. Thanks are due as well to Dr. Aurea Maria Ciotti of the Universidade de São Paulo, who helped us identify the species and the nature of the bloom.
As of February 5, 2014, the bloom appeared to be subsiding, though clouds and haze made it difficult to see clearly from satellites. You can continue to monitor the area by clicking here.
February 3rd, 2014 by Adam Voiland
Halos have a long and rich history in religious art, usually symbolizing the presence of someone or something divine. In the physical sciences, the beautiful displays of light are a sign of something more ordinary—the presence of hexagonal, plate-shaped ice crystals that make up cirrus clouds. As gravity pulls the ice crystals downward, their faces become horizontal with the ground and they function as dispersive prisms, breaking sunlight into separate colors and leaving rainbow-like ice crystal halos in the sky.
Sundogs are one of the most common types of ice halo. They occur when light rays enter the side of an ice crystal and leave through another side inclined about 60 degrees to the first. (See Atmospheric Optics for a good diagram that illustrates the process.) Sundogs are most easily seen when the Sun is low in the sky; the halos occurring on either side of it at about 22 degrees. The part of a sundog closest to the Sun always forms a layer of red, while greens and blues form beyond that. Sundogs are visible all over the world and at any time of year, regardless of the temperature at the surface. For more imagery of sundogs and other optical phenomena (such as sun pillars, circumhorizonatal arcs, and parhelic circles), it’s worth checking out the archives of Earth Science Picture of the Day.
In the last few weeks, we’ve had a number of readers send us their photographs of sundogs. The image above was taken by Nina Garcia Jones; the image below comes from Isa DeSil. Thanks for sending the photos our way. To the rest of our readers: keep your interesting photos of atmospheric, meteorological, or geological phenomena coming. We’ll occasionally post the best images on this blog, and we’ll do what we can to help explain the science behind them.