CSIRO and NASA collaborate for near real time analyses of volcano plume

The AeroSpan Network has assisted NASA in tracking the volcanic plume from the Hunga Tonga volcano which erupted between 14-15 January 2022. AeroSpan (Aerosol characterisation via Sun Photometry Australian Network) is a network of ground stations that continually measure aerosol properties across regions of Australia using Cimel sun photometers. Four of the ground stations detected the volcanic plume after it entered the upper troposphere and lower stratosphere moving westward from Lucinda (QLD), across Jabiru (NT) and Lake Argyle (WA) to Learmonth (WA).

The AeroSpan data was sent to NASA AERONET (aeronet.gsfc.nasa.gov) and has enabled near real time assessment of aerosol characteristics and supported rapid response satellite retrievals of this volcanic plume as it expanded across the Earth downwind from Hunga Tonga volcanic eruption.

Volcanic Plume erupting and travelling west across Australia (Himawari-8).

Solar Data Effect

The volcanic plume visibly affected the normal visual sun intensity data as seen at the various ground stations and although not as prominent at Lucinda or Jabiru due to existing cloud cover, both Lake Argyle and Learmonth gave clear indications of the upper atmospheric disturbance.  The intensity of the plume had dissipated after traversing the continent from east to west and Learmonth could only “see” the edge of the resulting plume.

These plots show the intensity (as digital counts) of the solar radiation at different wavelengths measured by the Cimel sun photometers as a function of time of day at Lucinda (top) and Learmonth (bottom). As expected, maximum solar radiation levels are measured during the middle of the day. Dips in the solar radiation curves indicate the presence of aerosols that reduce the amount of solar radiation reaching the instrument.

Analysis of the data was undertaken by AERONET to determine the aerosol optical depths (AODs) present due to the event.  AOD is used to estimate the amount of particulate present by measuring a ray of light as it passes through the atmosphere.

The AOD at ~500nm varied significantly from ~0.3 to 1.7 across three sites in northern Australia with fine mode particles in the volcanic plume with Angstrom Exponent varied widely from ~0.8 to 1.6 with increasing transit distance. The AERONET size distributions showed decreasing concentration with increasing size with time and distance of the fine mode.  This change may indicate SO₂ gas conversion to sulfate particles and hygroscopic growth.

The plot on the left shows the aerosol optical depth calculated from the Cimel sun photometer data at each AERONET site. The plot on the right shows aerosol size distributions at Lucinda and Learmonth.

Outcomes

This event highlights the importance of the AeroSpan network in contributing to global efforts to track the health and radiative properties of the atmosphere. Aerosol measurements performed by AERONET and through support by collaborators such as CSIRO (AeroSPAN) and Integrated Marine Observing System (IMOS), enables NRT (near real time) assessment of aerosol characteristics and supports rapid response satellite retrievals in tracking of atmospheric phenomena across the Earth.

Acknowledgements

The operation of AeroSpan is funded by CSIRO.  In addition, IMOS funded through the National Collaborative Research Infrastructure Strategy (NCRIS) is acknowledged for funding the AERONET site at the Lucinda Jetty Coastal Observatory.  Operational assistance is appreciatively provided to CSIRO by a network of remote site field managers.

(David Giles (NASA), Brent Holben (NASA), Thomas Eck (NASA), Melita Keywood (CSIRO), David Barker (CSIRO), Ian Lau (CSIRO), Thomas Schroeder (CSIRO), Ralph Kahn (NASA), and Ilya Slutsker (NASA))