CHAMPAIGN, Ill. -- Atmospheric measurements made at Earth's geographic poles provide a convenient way of validating and calibrating global circulation models. Such measurements also might provide some of the first conclusive evidence of global change in the middle and upper atmospheres. But new data shows that the current models are wrong: Temperatures over the South Pole are much colder in winter than scientists had anticipated.
Gardner's group was the first to make upper atmosphere temperature measurements over the South Pole. From December 1999 until October 2001, the scientists operated a laser radar (lidar) system at the Amundsen-Scott South Pole Station. By combining the lidar data with balloon measurements of the troposphere and lower stratosphere, the scientists recorded temperatures from the surface to an altitude of about 70 miles.
"Our results suggest that wintertime warming due to sinking air masses is not as strong as the models have assumed," Gardner said. "But, in all fairness, since no one had made these measurements before, modelers have been forced to estimate the values. And, in this case, their estimates were wrong."
"Current global circulation models apparently overpredict the amount of down-welling, because they show warmer temperatures than we observed," Gardner said.