Walker Circulation
UM Rosenstiel School researchers find new evidence for
weakening of Walker circulation.
(November 5, 2015) A
new analysis using changes in cloud cover over the tropical Indo-Pacific Ocean
showed that a weakening of a major atmospheric circulation system over the last
century is due, in part, to increased greenhouse gas emissions. The findings
from researchers at the University of Miami (UM) Rosenstiel School of Marine
and Atmospheric Science provide new evidence that climate change in the
tropical Pacific will result in changes in rainfall patterns in the region and
amplify warming near the equator in the future.
“Our findings show that an increasing concentration of
greenhouse gases leads to significant changes in atmospheric circulation and
tropical rainfall patterns,” said Katinka Bellomo, an alumna of the UM
Rosenstiel School. “This study demonstrates that we can predict these changes
in the Walker circulation from changes in cloud cover.”
The UM Rosenstiel School researchers used historical
observations of cloud cover as a proxy for wind velocity in climate models to
analyze the Walker circulation, the atmospheric air flow and heat distribution
in the tropic Pacific region that affects patterns of tropical rainfall. Their
findings revealed a weakening and eastward shift of the Walker circulation over
the last century due to greenhouse gas emissions. The analysis showed that changes in cloud
cover can serve as a proxy in climate models for wind velocity in the
atmosphere, which cannot be directly measured.
“This study makes innovative use of a decades old-dataset,”
said Amy Clement, professor of atmospheric science at the UM Rosenstiel School.
“It is impressive that visual observations from the decks of ships transiting
the Pacific Ocean over a half-century can tell us something so fundamental
about climate change.”
This new information can be incorporated into current
climate models to predict future changes in the magnitude and pattern of the
Walker Circulation due to increased greenhouse gas emissions. The study
suggests that rainfall will decrease over Indonesia and in the western Pacific
and increase over the central Pacific Ocean.