(December 22, 2015) All
over the planet, every day, oceans send plumes of sea spray into the
atmosphere. Beyond the poetry of crashing ocean waves, this salt- and
carbon-rich spray has a dramatic effect on the formation and duration of
clouds.
Yes, clouds, which cover 60 percent of the Earth’s surface
at any given time. In a new study in Proceedings of the National Academy of
Sciences, online Dec. 21, Colorado State University’s Paul DeMott, a senior
research scientist in the Department of Atmospheric Science, says sea spray is
a unique, underappreciated source of what are called ice nucleating particles –
microscopic bits that make their way into clouds and initiate the formation of
ice, and in turn affect the composition and duration of clouds.
“The presence of these particles is critically important for
precipitation and the lifetime of clouds, and consequently, for their radiative
properties,” said DeMott, who works in the lab of Sonia Kreidenweis, professor
of atmospheric science, associate dean for research in the College of
Engineering and a University Distinguished Professor.
Clouds’ effect on climate
Clouds, with their ability to reflect solar energy and
absorb terrestrial radiation, have dramatic effects on climate. Their radiative
properties are greatly influenced by the number, size and type of droplets and
ice particles inside the cloud. These cloud particles can initiate from any
number of sources of aerosols – particles suspended in air – from land and
ocean surfaces. From desert dust to burning fossil fuels, aerosols that affect
clouds are everywhere.
DeMott’s study has confirmed that ice nucleating particles
from oceans are distinct, both in their abundance as well as their ice-making
properties, from land-sourced particles. Hence, their influence on the
liquid/ice phase structure of clouds, and their subsequent radiative impacts,
can differ over vast swaths of Earth.