# Transient ice ring observed during the 15 January 2022 eruption of Hunga volcano

## TL;DR

A volcanic eruption in 2022 created a temporary ice ring in the atmosphere, offering insights into ice particle formation under extreme conditions.

## Contribution

The study identifies and models a transient ice ring formed by atmospheric waves from a volcanic eruption, revealing ice nucleation dynamics.

## Key findings

- A ring of small ice particles (~2 μm) formed around the volcanic plume in the upper troposphere-lower stratosphere.
- Atmospheric waves from the eruption caused temperature oscillations leading to ice particle formation via vapor deposition.
- The event provides a natural experiment to study ice nucleation and growth under abrupt temperature changes.

## Abstract

The eruption of Hunga volcano on 15 January 2022 was an exceptional event in the satellite era. Record-breaking heights of the volcanic plume were reported, a large amount of water was injected into the stratosphere and a broad spectrum of atmospheric waves were detected. Here, we use satellite measurements to show that a transient ring of small ice particles (~2 μm) formed around the plume. We hypothesize that the ice ring was generated by the passage of an atmospheric wave triggered by a pressure pulse at the surface corresponding to a violent explosion that occurred during the 15 January 2022 eruption sequence. The passage of the atmospheric wave produced a transient rarefaction in the upper troposphere-lower stratosphere, which in turn led to oscillations in ambient temperature. Due to the supersaturated state of the atmosphere with respect to ice, ice particles formed in the wake of the radially propagating atmospheric wave, allowing an exceptional opportunity to study ice particle growth via vapour deposition. This atmospheric phenomenon serves as an important natural experiment that reveals the time scale on which ice particles nucleate and grow given an abrupt perturbation in ambient temperature.

Ambient temperature oscillations in the wake of an atmospheric wave generated by the eruption of Hunga volcano in 2022 formed a temporary ring of small ice particles in the upper troposphere-lower stratosphere, according to satellite observations and ice nucleation modelling.