Science in Antarctica

Antarctica may be at the bottom of the world, but it's at the top of the weather system, says McMurdo weatherman Mike Osterhouse, and that makes it a very interesting and challenging place to do weather.

Probably the most unique thing about Antarctica, weatherwise, is that it is the "radiator for the world." Antarctica radiates heat. The snowy, icy mass of the continent does not absorb heat, instead it sends what Mike calls "a lot of bossy cold air" into the planetary weather system, creating currents. The heat from the continent radiates aloft, leaving the dense cold air to sink to the surface, where it eventually spills off in what Mike calls "glacial outflow." That same cold air that hovers at the surface of the continent is what causes something called fata morgana, or cold mirages. You look at the horizon and think you see shimmering glacier edges in the distance, or towering icebergs, but they are only an illusion.

Some people refer to Antarctica as a "cold sink," meaning the cold air keeps pouring in the top of the system, sinking, then flowing out at the bottom. All this activity causes something called the Polar Vortex, masses of warm and cold air mixing and shifting at the top of the system.

The cold air that spills off the continent is called Antarctic air-it is dry and cold. It moves out over open water and modifies-it absorbs moisture out there in the sea and takes on a different name-maritime polar air, which is moist and cold. This moist cold air moves toward the equator and encounters maritime tropical air and creates cold fronts or warm fronts. When it gets closer and closer to the equator it gets over warm moist water and will absorb heat. Then it becomes tropical air again that will rise and then go back over the poles and start the process all over.

As Mike and I are talking on this day in the weather room full of glowing computer screens showing satellite images of Antarctica, graphs charting out wind speed, air pressure and humidity, the wind is howling outside, buffeting the windows, screaming around corners and in cracks in the windows. Out the window we can see only white. Visibility is less than 1/8 of a mile. The wind is blowing at nearly 50 knots, which is nearly 60 miles an hour (at one knot the air is virtually still-moving at approximately 1.15 miles per hour). A weather advisory has gone out-it is Condition Two in town and Condition One everywhere else. Condition One exists when any of the following are true-the visibility is less than 100 feet, the wind speed is 55 knots or greater, or the wind chill is minus 100 F or colder. Condition One means stay put, stay inside. The temperature today is minus 114 F with the windchill.

Of course the cold--cold like this--cold as cold and even colder than minus 114 F-- is another thing that makes Antarctica unique. How cold is it really in Antarctica, I wanted to know. Here's how cold it is, says Mike, so cold that there have been two recorded cases of rain at McMurdo. "I think Shackleton recorded freezing rain once," he says. "We never ever get thunderstorms. When it is minus 30 and you inhale you can feel the inside of your nose freeze. The warmest it's ever been at McMurdo is 49 degrees in January 1974, and the coldest it's ever been was minus 59 in July." Minus 50 might not seem so cold, but when you add the windchill factor to minus 59 it gets much much colder. Mike says that originally wind chill measurements were pretty primitive. "The way they first determined windchill was how fast a hunk of meat would freeze outside." For those of you out there who are REALLY interested the equation for how to calculate windchill looks like this:

Antarctica is also incredibly dry-in fact it is the driest place on the planet. The average humidity is around 5-9 percent, indoors, which, for many people causes problems with dry skin, bloody noses, raw throats, and dry eyes. Outside, the relative humidity may be much higher--up to 50-80 percent, but when that cold air is warmed, you increase its capacity to hold moisture, without adding any real moisture, so the relative humidity drops dramatically. Cold air, says Mike, just can't hold moisture. Moisture precipitates out of cold air. By the time the air we breathe in Antarctica gets to Antarctica it has already traveled around the globe and its water has been squeezed out. By the time it gets here it is bone dry.

Like all the workstations at McMurdo, this one has its own brand of humor. One of the signs on the wall reads: "Turn on the weather channel. Chicks dig weather." Another sign reads: " We have successfully predicted 14 out of the last 4 Ross Island Storms." Mike laughs and says that they tend to overpredict here, because the safety of lots of people depends upon it. Their primary job is to forecast weather for aviation, for ships south of 60 degrees south, and for scientists who are out in field camps. Forecasting here is hard job, Mike says. "It's almost like forecasting typhoons. They pretty much tend to go wherever they want to go." Another sign on the wall says, "Meteorology is not an exact science." In fact, says Mike, it's an art, not a science at all. In the corner of the room there is a fake Ficas tree that has but one or two green leaves still clinging to it and one or two rather forlorn Christmas ornaments. "That was our winterover Ficas," someone says. Each day during the winter the weather folks picked leaves off, counting the days. "When they go," Mike says of the remaining leaves, "all we'll have left is a very ugly tree."

One of the big challenges of doing weather in Antarctica is the lack of data. In the states, says Mike, there are thousands of weather offices, but here there is really a lack of meteorological data. The three main weather stations in Antarctica are at the South Pole, Palmer station on the Antarctic Peninsula, and McMurdo. Much of the weather data that Mike and his co-workers use to predict the weather comes to them via automatic weather stations placed at various locations out on the ice. Polar orbiting satellites pick up the data from the stations and relay it to McMurdo. Weather data is also collected through local McMurdo sensors that measure wind, temperature, and pressure. They also get weather data from balloons that they send up, which measure temperature, pressure, humidity, and winds. Since flight safety and field safety are the main forecasting concerns of McMurdo's weathermen, when weather data first comes in it is used to forecast for pilots and field parties. But McMurdo's weather data is also sent to the U.S., where it is incorporated into global weather models that are used to make 12, 24, and 36-hour forecasts over the entire planet. The computers that generate the forecasts are "data hungry" Mike explains. They need lots of information. "We are just a small part of that puzzle, but a pretty important part," Mike says.

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