Atmospheric Sciences News

Climate Clues from One of the Rainiest Places on Earth

One of the world’s rainiest places lies off Colombia’s Pacific coast. New field research sheds light on the Chocó low-level jet, a phenomenon responsible for the region’s precipitation.


A jet stream known as the Chocó low-level jet (the ChocoJet) connects the Pacific Ocean with western Colombia. It helps dump more than 9,000 millimeters of rain each year, making the area offshore of the Colombian town of Nuquí one of the rainiest places on the planet.

“The ChocoJet—this low-level flow—is a physical bridge between the sea surface temperatures and sources of moisture in the Pacific, and the climate patterns of western South America,” said John Mejia, an associate research professor of climatology at Nevada’s Desert Research Institute and lead author of a new paper on the phenomenon.

In addition to its regional impact, the ChocoJet plays a role in the El Niño–Southern Oscillation (ENSO), a climate pattern whose variations can signal droughts and floods for Colombian farmers. ENSO also has significant impacts on Europe, Africa, Asia, and North America.

“In the atmosphere, we are all connected,” Mejia said, and the ChocoJet “is part of the engine that redistributes the heat from the tropics to higher latitudes.”

Rainy Puzzle

In 2019, after 6 months of preparations, Mejia and his team were able to get enough helium tanks and sonde balloons to this remote region (accessible by only sea or air). They launched the balloons up to four times a day over 51 days, resulting in new data on temperature, winds, and other atmospheric conditions.

They detailed their findings in a recent paper published in the Journal of Geophysical Research: Atmospheres. The new data contribute to a better understanding of the dynamics and thermodynamics of the ChocoJet’s processes, which have implications for regional wildlife and agriculture, as well as for natural hazards. Mejia said the main contribution of the field campaign in Nuquí and the resulting data was to find out why and how these precipitation mechanisms produce one of the rainiest places on Earth, with the added benefit of building on the very scant climate data gathered previously. “This is a field experiment that can help test climate models.…Figuring this out can make global models more accurate,” Mejia said.

Alejandro Jaramillo, a hydrologist at the Center for Atmospheric Sciences at the National Autonomous University of Mexico, said that more observations will allow for a better model, which will lead to better prediction of rainfall and major weather events, like hurricanes. Jaramillo was not involved in the new research.

“If you better understand the processes that are causing this high rainfall, you can find better ways for climate models to fill in the gaps where there [aren’t] hard data,” Jaramillo said.

Impacts Beyond Climate

According to Germán Poveda, a coauthor on the recent study and a professor at the National University of Colombia, the project not only aimed to understand the dynamics and thermodynamics that explain the rainiest region on Earth but also was an opportunity to train Colombia’s next generation of climate scientists.

Juliana Valencia Betancur, for instance, was an undergraduate environmental engineering student at Colegio Mayor de Antioquia in Medellín during the Nuquí field campaign. She and a half dozen other undergraduate students were in Nuquí to help prepare and launch balloons as part of their research undergraduate experience.

Students in Nuquí, Chocó, Colombia, prepare to launch a sonde balloon during the fieldwork campaign.
Students from Institución Educativa Ecoturistica Litoral Pacifico in Nuquí prepare to launch a sonde balloon during the fieldwork campaign. Credit: Organization of Tropical East Pacific Convection (OTREC) participants/John Mejia

“I hadn’t had much interest in atmospheric science, but after Nuquí, with all the marvelous things I learned, my outlook changed completely, and my professional career changed course,” she said, adding that she is now looking for graduate opportunities in atmospheric science.

Johanna Yepes, a coauthor and researcher based at Colegio Mayor de Antioquia, said Nuquí’s local schoolchildren also benefited from the project’s outreach activities. During the field campaign, the researchers visited Nuquí’s only school and, with enthusiastic support of the principal, presented their project to students in the fourth to seventh grades. The students were also invited to visit the launch site, and two of them got a chance to launch a sonde balloon themselves.

“For me, it was the most beautiful part, putting what we were doing in very simple words and seeing how the children understood the daytime cycle of rain, sometimes even better than we did ourselves,” Yepes said.

—Andrew J. Wight (@ligaze), Science Writer

Citation: Wight, A. J. (2021), Climate clues from one of the rainiest places on Earth, Eos, 102, Published on 07 June 2021.
Text © 2021. The authors. CC BY-NC-ND 3.0
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