University of Washington scientists are part of an international team that is spending six weeks in the remote Southern Ocean to tackle one of the region’s many mysteries: its clouds.
What they discover will be used to improve climate models, which routinely underestimate how much solar energy bounces off clouds in that region. Simulating how much solar energy is absorbed or reflected on Earth is key to calculating the future of the planet under climate change.
The Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study, or SOCRATES, could also help scientists understand the very nature of how clouds interact with aerosols — natural or human-made particles that are suspended in the atmosphere. Aerosols can cause clouds to form, change their structure and affect precipitation, all of which affect the amount of energy that reaches the surface.
During the mission, which runs from mid-January through, the scientists are collecting data from air and sea. Observations are being taken from the High-performance Instrumented Airborne Platform for Environmental Research, or HIAPER, a highly modified aircraft operated by the NSF and the National Center for Atmospheric Research, and the R/V Investigator, an Australian deep-ocean research vessel.
“Much of what we currently know about Southern Ocean cloud, aerosol and precipitation properties comes from satellite-based estimates, which are uncertain, and have undergone few comparisons against independent data,” said team member Roger Marchand, a UW research associate professor of atmospheric sciences. “The data collected during SOCRATES will also enable us to evaluate current satellite data over the Southern Ocean, as well as potentially help in the design of better satellite-based techniques.”
The research aircraft based out of Hobart, Tasmania, will make about 16 flights over the Southern Ocean. Instruments will measure the size and distribution of cloud droplets, ice crystals and aerosols. The data will help test the theory that climate models may not be producing enough supercooledwater — droplets that stay liquid even when the temperature is below freezing.
Measurements will also provide a look back in time to see how the atmosphere behaved in a time when it contained fewer human pollutants.
“It can be difficult to find truly pristine conditions in the Northern Hemisphere,” said Robert Wood, a UW professor of atmospheric sciences. “By studying the more pristine Southern Ocean region, we hope to be able to learn about what conditions may have been like in the Northern Hemisphere in the pre-industrial period.”
The measurements taken from the sky will be complemented by data collected from the R/V Investigator. The ship’s team will launch soundings every six hours, and sometimes more often, throughout the campaign.
The U.S. portion of SOCRATES is largely funded by the National Science Foundation.
“The Southern Ocean is famously remote and stormy and it’s hard to imagine a worse place to do a field campaign. But a vast, stormy ocean is a great laboratory for studying clouds, and it’s clear from our models that we have a lot to learn about them,” said Eric DeWeaver, program director in NSF’s geoscience directorate.
SOCRATES investigators will also incorporate other ocean measurements and data from land-based instruments on Macquarie Island that UW scientists installed in 2016.
“SOCRATES will allow for some of the best observations of clouds, aerosols, radiation, and precipitation that have ever been collected over the Southern Ocean,” said principal investigator Greg McFarquhar, at the University of Oklahoma. “These data will provide us with critical insight into the physics of cloud formation in the region, information we can use to improve global climate models.”
Source: University of Washington