Research team first to observe new patterns of equatorial winds in Antarctica

A team led by CIRES has discovered a critical link between winds at Earth’s equator and atmospheric waves 6,000 miles to the South Pole. The team found, for the first time, evidence of a quasi-biennial oscillation (QBO) – a pattern of atmospheric circulation that originates at the equator – at McMurdo, Antarctica.

The discovery highlights how winds in the deep tropics affect the distant South Pole, particularly the polar vortex, which can trigger spikes in cold temperatures in mid-latitudes. Scientists will be able to use this information to better understand weather and climate conditions on the planet and fuel more accurate atmospheric models, the authors say.

“We have now seen how this atmospheric model propagates from the equator to the high latitudes of Antarctica, showing how these distant regions can be linked in ways that we did not know before,” Zimu Li said, former CIRES Research Assistant who did this work at the University of Colorado at Boulder, and lead author of the study today in the Journal of Geophysical Research: Atmospheres.

“It can improve our understanding of how large-scale atmospheric circulation works and how patterns in one region of the world can spread around the world,” said Xinzhao Chu, member of CIRES, professor in the department of aerospace engineering by Ann & HJ Smead. Sciences at the University of Colorado Boulder, and corresponding author on the new work.

Every two years or so, the QBO causes the stratospheric winds at the Earth’s equator to change direction, alternating between east and west. Lynn Harvey, a researcher at UC’s Laboratory for Atmospheric and Space Physics (LASP) and co-author of the study, helped the team study polar eddies, the huge vortices of cold air that swirl overhead from each of the Earth’s poles. The study reports that the Antarctic vortex expands during the QBO phase to the east and contracts during the west phase. The team suspects that when QBO alters the behavior of the polar vortex, this in turn affects the behavior of atmospheric waves called gravity waves, which pass through different layers of the atmosphere. They identified specific types of changes in these gravity waves: The waves are stronger during the eastern period of the QBO and weaker when the QBO is in the west.

Over the past nine years, members of Chu’s lidar team have spent long seasons at McMurdo Station, Antarctica, braving 24-hour darkness and freezing temperatures to operate custom lasers and measure models. in the earth’s atmosphere. These long-term measurements, along with 21 years of atmospheric surveys from NASA MERRA-2, were critical to the new discoveries. Each QBO cycle takes years to complete, so long-term data feeds are the only way to identify interannual connections and patterns.

“Atmospheric scientists can use this information to improve their models – before that, no one really knew how QBO impacts gravity waves in this polar region,” said Xian Lu, a researcher at Clemson University and co-author of the ‘study. “Researchers can use this information to better model and predict climate, including atmospheric and spatial variability and long-term changes.”