Volcanic Aerosols from Hunga Tonga Eruption Detected in Northern Hemisphere Stratospheric Westerlies

Scientists from the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences, leading an international team, have discovered aerosols from the Hunga Tonga eruption in the stratospheric westerlies of the Northern Hemisphere for the first time. The discovery, published in Science Bulletin, will help scientists to simulate the physical and chemical processes in volcanic plumes.

The Hunga Tonga-Hunga Ha’apai volcano, located in the South Pacific Ocean, erupted in January 2022, and scientists worldwide closely monitored it as one of the largest recent eruptions.

The Sounding Water vapor, Ozone, and Particle (SWOP) campaign aims to better understand the temporal and spatial distribution characteristics of atmospheric compositions over the Tibetan Plateau. The campaign’s balloon-borne payload, consisting of the Compact Optical Backscatter Aerosol Detector (COBALD) and the Portable Optical Particle Spectrometer (POPS), was released in Lijiang, Yunan province on April 9, 2022. The balloon unexpectedly captured the size spectrum of volcanic aerosols at 24–25 km.

Impact on Regional and Global Atmospheric Circulation and Climate

The Hunga Tonga volcanic aerosol was identified by the size distribution of the aerosol diameter, which was larger than the background mode of stratospheric aerosols. The particle number densities were approximately 1 cm-3. The backscatter ratios derived from the COBALD measurements showed enhanced aerosol signals between 24 and 25 km. Measurements also showed that the aerosol and water vapor layers were separated in the Hunga Tonga plume.

The findings suggest that volcanic eruptions can impact regional and global atmospheric circulation and climate, even thousands of kilometers away from the source. It also suggests that large uncertainties still remain in understanding the physical properties and evolutionary process of volcanic aerosols in the stratosphere.

In-situ measurements obtained in volcanic plumes provide compelling evidence that reduces these uncertainties. However, it is difficult to obtain these parameters, especially during the occurrence of volcanic eruptions. The possible mechanisms that led to the separation of aerosol and water vapor layers in the Hunga Tonga plume will be examined in future studies.