Our team at Summit Station has been offering glimpses of the light show they're witnessing as the north polar region slips into darkness.
A sundog forms as the sun sets. Photo: shawntel stapleton
These optical effects are caused by light bending through ice crystals. The specific light show captured above suggests there are "plate-shaped hexagonal ice crystals in the atmosphere," wrote ICECAPS science technician, Lana Cohen. Different crystal shapes can create different effects, as explained in posts contributed by Ed Stockard in previous winter seasons.
The science team also sent some snowflake images captured during last week's storms.
Taken with a camera attached to a microscope, "these images are invaluable for providing a link between what is remotely sensed [via instruments monitoring conditions for Von Walden's NSF-funded ICECAPS project] with the instruments and what we actually see on the ground," Lana explained. For more on ICECAPS science, read this post: http://www.polarfield.com/blog/?s=snowflake.
Intricate as they are, "these snowflakes are not the same as the plate-shaped ice crystals that create the sundogs and halos," notes Lana. "They form from very different processes in the atmosphere. And those different processes are exactly what we are trying to study with the ICECAPS project!"
In addition to University of Idaho's Von Walden, the ICECAPS collaboration includes PIs Matt Shupe (University of Colorado), Dave Turner (NOAA), and Ralf Bennartz (University of Wisconsin).
We have three such science technicians at Summit right now: Lana Cohen, who is dedicated to ICECAPS research, shawntel stapleton, who looks after two dozen or so experiments for a variety of PIs, and Dave Benson, dedicated to NOAA's Arctic Atmospheric Observatory Program.
Brad Whelchel, station manager, sent a photo of a mirage, a Fata Morgana.
These mirages appear when a cool mass (in this case, the ice sheet) is topped by a warm air mass, creating a thermal inversion. Light is bent through these opposing air layers. "The thermal inversion must create an 'atmospheric duct' strong enough to bend the light rays more than the curvature of the Earth," Brad explained. "The effect usually creates inverted [upside-down] and upright images stacked on top of each other." In the picture above, the 3-mile marker on the skiway in the distance appears to be twice as tall as the two markers closer in - that's the most obvious evidence of the 'stacking' images created by a mirage.
This may be the first image of a Fata Morgana we've seen from Summit Station, so we asked Brad if they are rare around Summit. "We've seen them plenty of times up here; it's just hard to get a photo because normally there is only ice on the horizon," Brad explained. In other words, Fata Morgana are difficult to shoot on an ice sheet because ice sheets tend to offer little visual relief - mountains, for example - that effectively show the distortion created by the mirage.
"This time, the thermal inversion moved in close and distorted the 3-mile visibility marker. I was able to get a photo of it by setting my point-and-shoot digital camera to macro mode, pressing it to the eye-cup of the binoculars, and holding it really steady." Cool!
We should mention that five busy PFS seasonal staffers presently occupy Summit for the CH2MHILL Polar Services team. In addition to Brad and the science technicians, Ian McEwen is on site as our mechanic. We'll see if we can get Brad to send us a photo of the five. --Kip Rithner