Sep 01

New Clues to Origins of Mysterious Atmospheric Waves in Antarctica

Two years after a CIRES and CU Boulder team discovered a previously unknown class of waves rippling continuously through the upper Antarctic atmosphere, they’ve uncovered tantalizing clues to the waves’ origins. The interdisciplinary science team’s work to understand the formation of “persistent gravity waves” promises to help researchers better understand connections between the layers of Earth’s atmosphere—helping form a more complete understanding of air circulation around the world.

“A big picture of Antarctic gravity waves from the surface all the way to the thermosphere is emerging from the studies, which may help advance global atmospheric models,” said CIRES Fellow and CU Boulder Professor of Aerospace Engineering Sciences Xinzhao Chu, lead author of the new study published today in the Journal of Geophysical Research – Atmospheres. “The new understanding results from a series of journal publications, based on multiple years of lidar observations, many made by winter-over students, from Arrival Heights near McMurdo Station in Antarctica.”

In the 2016 paper, Chu and her colleagues discovered persistent gravity waves: huge ripples that sweep through the upper atmosphere in 3- to 10-hour periods. And now, by combining observations, theory, and models, they propose two possible origins of those waves: they are either from lower-level waves breaking and re-exciting new waves higher in the sky, and/or from polar vortex winds.

ince 2016, the team managed to track the origin of the upper atmospheric waves down to the lower-altitude stratosphere. The team then characterized the dominant gravity waves there, but found they had very different properties than the persistent waves in the upper atmosphere.

“The upper-atmosphere waves are huge, with a horizontal length of around 1,200 miles (2,000 km), and the lower, stratospheric waves are much smaller—only 250 miles (400 km),” said Jian Zhao, a Ph.D. candidate in CU Aerospace, working in Chu’s group, who stayed the 2015 winter over at McMurdo for lidar observations.

Zhao and colleagues previously described the stratospheric waves in an earlier study, and he is second author on the new study which describes how the wave energy varies over seasons and years—documenting those kinds of variations is critical for researchers trying to understand how the waves influence things like global air circulation and climate change.

click here to read the full story @ the cires webpage