Today is a very special day here at McMurdo Station because the sun will be popping up over the horizon at long last. It's been a long, long time without our bright, warm friend to light up this place. And with its return, we're about to recommence an age-old "tradition" called the Winter Fly-In, known for short as Winfly.

Winfly is typically a six-week long period beginning in August when the U.S. Antarctic Program flies in a few early season flights to bring in several hundred new people and supplies. This small surge in support helps the station ramp up for the arrival of all the science grantees at the beginning of the main summer field season in early October.

Photo Credit: Ryan Wallace Twilight glow as the first sunrise of 2011-12 approaches.

The first flight, carrying nearly 120 passengers aboard a U.S. Air Force C-17 Globemaster III from Joint Base Lewis-McChord , landed on the ice runway at Pegasus airfield shortly after noon on Aug. 20 (local time). Six flights are scheduled between Aug. 20 and Aug. 29.

Over the next month and a half, McMurdo will prepare for all sorts of summer science operations. Excursions out onto the sea ice will begin, including roadway flagging, ice runway preparations, ice-crack safety inspections, and also science dives under the ice. A couple of science groups will arrive during Winfly and work out of the fully prepared Crary Science Laboratory.

Among the groups is a team led by Adam Marsh from the University of Delaware who will scuba dive under the ice to collect a marine worm for research related to its climate-driven genetic adaptations. Jody Deming's team from the University of Washington will arrive during Winfly to search out frost flowers, delicate ice-crystal structures of high salt content that form on the surface of the sea ice around McMurdo. Deming wants to test a hypothesis that says wind-borne frost flowers transport marine bacteria over long distances.

Photo Credit: Dan Su Nacreous clouds above McMurdo Station.

This is probably one of the most interesting times of the year to be at McMurdo, because the average temperatures typically drop to the coldest levels of the year. It gives you the opportunity to enjoy the strongest feeling of being on the "harsh" continent.

One of the highlights of Winfly is that the sky frequently becomes adorned with the refracted apparitions of very high, sweepy cloud phenomena called nacreous clouds. These clouds take on a rainbow-like luminescence, as the low-angle sunlight passes through the ice crystals contained high within. The beauty is a double-edge sword. The clouds have been implicated in the atmospheric processes that cause ozone depletion, which also begins at this time of the year.

What makes Winfly most special is that you can really feel the return of the science mission here. Science is our bread and butter at McMurdo Station, and it's what we've been preparing for all winter long. The return of the sun illuminates that fact.