New high-altitude measurements have revealed a class of ultrafine particles rich in organic matter, until now undetected but widespread, in upper layers of the Earth’s atmosphere, and that play a fundamental role in the chemistry of the lower stratosphere.
The stratospheric aerosol layer, which extends from approximately 8 to 35 kilometers above the Earth’s surface, plays a crucial role in regulating the climate by reflecting sunlight and in chemical reactions that influence atmospheric composition.but knowledge of the particles that compose it remains incomplete.
Most of these particles now discovered have a diameter of less than 0.11 micrometers (approximately 100 times smaller than a grain of dust) and are surprisingly abundant in the lowest layers of the stratosphere, almost 11 kilometers above the surface, according to a study published Science.
“These particles have been practically invisible to us until now,” since most instruments and satellites do not detect them because they are too small, according to the lead author of the article, Ming Lyu, from the University of Colorado, an affiliate of the American National Oceanic and Atmospheric Administration (NOAA).
1/6 | Altocumulus clouds cover the skies of Puerto Rico. Altocumulus clouds in the Bayamón area on the morning of Friday, October 23, 2020. – Supplied
However, they are really abundant particles and, therefore, taken together, they can have a great impact, said the researcher cited by NOAA, an institution that also participated in the study.
Understanding these small particles is “critical to predicting how the stratosphere would respond to any type of disturbance, whether natural, such as a volcano, or caused by humans,” Lyu said.
The measurements were made during NOAA’s SABER (Stratospheric Processes, Balance and Radiation Effects) mission in February 2023, using a NASA WB-57 high-altitude aircraft equipped with a suite of highly specialized instruments.
The researchers found that this new type of ultrafine particles is associated with higher levels of nitrous oxide (N₂O), which is a common indicator of recent upward air movements from the surface (troposphere), as this element is only emitted at ground level from sources such as agriculture, industry and energy production.
Once formed in the upper troposphere from surface emissions, these organic-rich nanoparticles are transported into the stratosphere along with N₂O and other pollutants via tropical updrafts, convective storms, and the gradual rise of air in the tropics.
This discovery is “especially relevant” to the potential viability of stratospheric aerosol injection (SAI), a form of climate intervention that involves injecting particles or particle-generating gases, for example, sulfur dioxide, into the stratosphere to reflect sunlight and cool the planet, NOAA explained.
Charles Brock, also a signatory of the article, considered that if you are thinking about injecting sulfur dioxide vapor or other condensable gases into the stratosphere, these small background particles will be the first to which the new material adheres, which “changes everything in terms of the design and prediction of the effects.”
NOAA does not conduct SAI experiments in the atmosphere, so scientists use computer models to try to simulate its effects on weather and climate patterns.