It is one of the remaining challenges for weather and climate modelers: understanding how variations in cloud spatial patterns affect weather patterns over time.
Now, a University of Miami atmospheric scientist is part of a multiyear NASA-led field campaign that is using synchronized aircraft flights to unravel some of the mysteries surrounding the evolution of clouds during cold-air outbreaks—from thick, overcast to fluffy, cotton ball-like cumulus clouds.
“Sampling during cold-air outbreaks is one of the key elements of this project. We’re examining how low-altitude clouds change in form as cold air advects offshore,” said Paquita Zuidema, a professor at the University’s Rosenstiel School of Marine and Atmospheric Science, who is an investigator on the Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment, or ACTIVATE. “Models often underrepresent the ‘streets’ of shallow clouds and the often-dramatic change from more overcast to more broken clouds,” she explained.
“A critical uncertainty comes about because even in below-freezing temperatures, most of the composition of a cloud is typically liquid,” Zuidema added. “If, how, and when, the liquid becomes ice, and what that does to the cloud field organization remains a leading research question. We see similar cloud evolutions in fully liquid clouds at warmer temperatures, but have less of an idea of what to expect when ice can also be present. Knowing how much of a cloud is made up of liquid and how much is made up of snow and ice is a driving question for both weather and climate modeling.”
For the past two years, ACTIVATE researchers have deployed aboard two aircraft out of NASA’s Langley Research Center in Hampton, Virginia, flying over the western North Atlantic Ocean to collect critical data on the atmospheric structure, aerosol, and cloud physics not available through any other means.
“The two, small planes are both relatively slow-flying, allowing them to increase their sampling time and remain coordinated with each other,” Zuidema said.
The aircraft fly in synchronized fashion. While one plane flies through the clouds to take atmospheric readings, the second cruises directly above, gathering remote-sensing measurements and releasing probes that record crucial vertical structure readings.
The western North Atlantic is an ideal location for the study because of its proximity to cloud transitions. “Of further interest is that the continental air advects with a wide range of aerosol loadings, primarily from the industrial pollution of the East Coast. This can then mix in with much cleaner air coming from aloft and with the sea spray aerosols off of the ocean. So, there is a range of complexities to consider,” Zuidema said.
Data collected by the two NASA aircraft is downloaded to a web server, giving Zuidema and Rosenstiel School assistant scientist Seethala Chellappan the opportunity to analyze how cloud microphysical characteristics relate to the larger environment.
“We published an initial paper that looked at how effective reanalysis data—that is, data provided by models after they have assimilated satellite measurements—captured changes in the atmospheric temperature, humidity, and wind vertical profiles as air moved over the Gulf Stream,” Zuidema revealed. In that study, published in the September 8, 2021, online issue of AGUGeophysical Research Letters, Zuidema and her team found that reanalysis data are adequate for the purpose of initializing higher-resolution modeling of cold-air outbreak clouds.
The project, she said, has the potential to provide atmospheric scientists with decades’ worth of important information on the processes that dictate the life cycle of clouds, from their formation and maintenance to their eventual dissipation.
ACTIVATE research flights will continue through September, augmenting data from previous missions.
The University of Arizona is the lead academic institution on the project, which is one of five NASA Earth Venture Suborbital campaigns investigating little-understood aspects of our planet’s system processes.
The study is yet another example of Zuidema’s continued work in the exploration of clouds. Her research focuses on the relationship of warm, shallow clouds to the large-scale environment, with an emphasis on the connection to radiation.
She served as principal investigator of the five-year NASA-funded ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) project, studying how biomass burning aerosol particles produced by fires in Southern Africa impact climate.
Born in the Netherlands, Zuidema grew up speaking Dutch. She was just 4 when her father, a cultural anthropologist, moved her family to Peru for an academic teaching position. She earned a Bachelor of Science in physics from the University of Illinois at Urbana-Champaign, and later, a Ph.D. in atmospheric and ocean sciences from the University of Colorado-Boulder.
She became fascinated with clouds as a graduate student, writing a thesis on a satellite characterization project that involved low, shallow clouds.
“I absolutely love looking at clouds,” she said, “and wondering why they are.”
