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UM Researchers Head to the Clouds to Study Earth’s Climate

UM Rosenstiel School researchers conducting airborne experiment on low-lying clouds in Pacific.

MIAMI – Nearly 40 years after taking his first aircraft measurements of clouds off the California coast, University of Miami Professor Bruce Albrecht has returned again this month equipped with new state-of-the-art technologies to understand the effects of low-lying clouds on global climate.

“These low clouds are extremely important to the climate system because they reflect sunlight back to space, which provides the primary cooling of our planet,” said Bruce Albrecht, professor of atmospheric sciences at the UM Rosenstiel School of Marine and Atmospheric Science. “The processes through which cloud coverage will change as our planet warms remains largely uncertain in climate predictions.”

The first of 14-projected research flight aboard the state-of-the-art National Science Foundation (NSF) Gulfstream V research aircraft took off on July 1 from Sacramento, California to sample the trade wind-driven clouds as they move across the Pacific Ocean to Hawaii. During the nearly two month-long experiment, the research team is studying the process by which these low clouds – stratocumulus and cumulus – change shape as they move with the prevailing trade winds. The project is unique in that the same cloud areas sampled by the research aircraft on the flights to Hawaii are re-sampled two days later when the aircraft returns to California, allowing the evolution of the cloud systems to be studied.  

Stratocumulus and cumulus clouds both reflect solar radiation back into space, but in differing amounts. The process by which stratocumulus transitions into cumulus depends on many factors, not all well understood. To gather a more detailed picture of the clouds, Albrecht and his research team are sampling across a range of scales, from the fine particles called aerosols that “seed” the cloud droplets, to the large raindrops that deplete the clouds, and the larger thermodynamic environment to which the clouds are responding. Learning more about the finer details of these clouds is necessary to estimate the solar energy that eventually reaches Earth.

The research aircraft is equipped with new technology, such as an airborne Doppler cloud radar and an aerosol lidar, to provide the researchers with a better understanding of the cloud structure, aerosols, and precipitation, which will provide them with significant new insights on the role of these clouds on the global climate system.

“Our preliminary data are already revealing that aerosol-depleted environments are much more common than previously thought, changing textbook ideas on the low cloud lifecycle,” said Paquita Zuidema, professor of atmospheric sciences at the UM Rosenstiel School and co-investigator of the study.

“Due to improvements in long-distance research flight operations and technology, my dream of forty years has come true,” said Albrecht.

The NSF-funded study, AGS-1445832, also includes Rosenstiel School alumnus Virendra Ghate, from the University of Chicago; Chris Bretherton and Robert Wood from the University of Washington; and Rosenstiel School graduate student Mampi Sarkar. The Cloud Systems Evolution in the Trades (CSET) runs through August 15.

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About the University of Miami’s Rosenstiel School

The University of Miami is one of the largest private research institutions in the southeastern United States. The University’s mission is to provide quality education, attract and retain outstanding students, support the faculty and their research, and build an endowment for University initiatives. Founded in the 1940’s, the Rosenstiel School of Marine & Atmospheric Science has grown into one of the world’s premier marine and atmospheric research institutions. Offering dynamic interdisciplinary academics, the Rosenstiel School is dedicated to helping communities to better understand the planet, participating in the establishment of environmental policies, and aiding in the improvement of society and quality of life. For more information, visit:  www.rsmas.miami.edu.

Bruce Albrecht, with co-investigators
Bruce Albrecht University of Miami Rosenstiel School of Marine and Atmospheric Science (UM/RSMAS), with co-investigators Virendra Ghate, University of Chicago and Paquita Zuidema, UM/RSMAS, in front of the NSF Gulfstream-V.

The flight track from July 17
The flight track from July 17, shows the NSF NCAR Gulfstream G-V plane winding its way from California to Hawaii along pre-determined waypoints. The distance by which those airmasses transport in two days is calculated, and then the same airmasses resampled during the flight from Hawaii to California. The changes in cloud properties that typify the transition, from small completely overcast cells, to larger closed cells, to more broken clouds, are clearly visible in the satellite image.

Radar and lidar imagery from the flight back to California
Radar and lidar imagery from the flight back to California. These datasets, unprecedented for this region, will contribute to developing a comprehensive understanding of how aerosols and precipitation modify the clouds and their coverage of the underlying ocean, distinct from meteorology.

Clouds
Cloud photo taken during flight, showing the diversity in cloud shapes. The thin laminar clouds are much more frequent than investigators initially expected, and may represent environments in which few aerosols exist around which cloud drops can form.

Tags:
climate •  research •