For years, Brookhaven National Laboratory has employed thousands of Long Islanders and made discoveries that benefit our lives in many ways. Yet, few people know what actually happens inside the sprawling research campus in Upton.
One example is now emerging from BNL’s atmospheric science program, where researchers and collaborators have developed a powerful new laser-based instrument capable of observing cloud structures at the scale of a single centimeter. The technology offers scientists an unprecedented look at how clouds behave at their uppermost edges, a region that plays a critical role in weather and climate.
The instrument, a high-resolution form of lidar, a laser-based remote-sensing tool, allows scientists to directly observe fine cloud structures with detail 100 to 1,000 times sharper than traditional atmospheric lidars. Using laboratory-generated clouds, the team was able to study cloud-top features that until now could only be inferred indirectly.
The findings were published in the Proceedings of the National Academy of Sciences and provide some of the first experimental data showing how cloud droplets near the top of a cloud differ from those deeper inside. Those differences influence how clouds reflect sunlight, form precipitation, and affect Earth’s energy balance.
“This is the first time we’ve been able to see these cloud-top microstructures directly and non-invasively,” said Fan Yang, an atmospheric scientist at Brookhaven and lead author of the study. “They occur on scales smaller than most atmospheric models consider, yet they can strongly affect cloud brightness and rainfall.”
The custom-built lidar was designed in collaboration with Yong Meng Sua of the Stevens Institute of Technology. It uses ultrafast laser pulses and single-photon detection to build highly detailed profiles of cloud droplet distributions.
Testing took place in a controlled cloud chamber at Michigan Technological University, where researchers found that cloud tops contain fewer droplets than the cloud interior. Scientists attribute this to dry air mixing into the cloud from above and to heavier droplets settling downward due to gravity.
Yang said many atmospheric models oversimplify these processes, potentially introducing major uncertainty into weather and climate predictions.
Brookhaven scientists plan to expand the research using a newly constructed cloud chamber at the laboratory, allowing faster experimentation, improved sensor calibration, and a stronger connection between lab studies and real-world atmospheric measurements.
The work was supported by the U.S. Department of Energy’s Office of Science, along with the National Science Foundation and the Simons Foundation.