Journal cover Journal topic
Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

Journal metrics

  • IF value: 3.089 IF 3.089
  • IF 5-year<br/> value: 3.700 IF 5-year
  • CiteScore<br/> value: 3.59 CiteScore
  • SNIP value: 1.273 SNIP 1.273
  • SJR value: 2.026 SJR 2.026
  • IPP value: 3.082 IPP 3.082
  • h5-index value: 45 h5-index 45
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
06 Feb 2017
Review status
A revision of this discussion paper was accepted for the journal Atmospheric Measurement Techniques (AMT) and is expected to appear here in due course.
Retrieval of volcanic SO2 from HIRS/2 using optimal estimation
Georgina M. Miles1,2, Richard Siddans2, Roy G. Grainger1, Alfred J. Prata1,3, Bradford Fisher4, Nickolay Krotkov5, and Brian Kerridge2 1Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK
2Remote Sensing Group, STFC Rutherford Appleton Laboratory, Harwell Oxford, UK
3Nicarnica AS, Lysaker, Norway
4Science Systems and Applications, Inc, 10210 Greenbelt Road, Suite 600, Lanham, Maryland, USA
5Goddard Space Flight Center, Greenbelt, Maryland, USA
Abstract. We present an optimal estimation (OE) retrieval scheme for stratospheric sulphur dioxide from the High Resolution Infrared Radiation Sounder 2 (HIRS/2) instruments on the NOAA and MetOp platforms, an infrared radiometer that has been operational since 1979. This algorithm is an improvement upon a previous method based on channel brightness temperature differences developed by Prata et al. (2003), which demonstrated the potential for monitoring volcanic SO2 using HIRS/2. The Prata method is fast but of limited accuracy. This algorithm uses an optimal estimation retrieval approach yielding increased accuracy for only moderate computational cost. This is principally achieved by fitting the column water vapour and accounting for its interference in the retrieval of SO2. A cloud and aerosol model is used to evaluate the sensitivity of the scheme to the presence of ash and water/ice cloud. This identifies that cloud or ash above 6 km limits the accuracy of the water vapour fit, increasing the error in the SO2 estimate. Cloud top height is also retrieved. The scheme is applied to a case study event, the 1991 eruption of Cerro Hudson in Chile. The total erupted mass of SO2 is estimated to be 2300 kT ± 600 kT. This confirms it as one of the largest events since the 1991 eruption of Pinatubo, and of comparable scale to the Northern Hemisphere eruption of Kasatochi in 2008. This retrieval method yields a minimum mass per unit area detection limit of 3 DU, which is slightly less than that for the Total Ozone Mapping Spectrometer (TOMS), the only other instrument capable of monitoring SO2 from 1979–1996. We show an initial comparison to TOMS for part of this eruption, with broadly consistent results. Operating in the infrared (IR), HIRS has the advantage of being able to measure both during the day and at night, and there have frequently been multiple HIRS instruments operated simultaneously for better than daily sampling. If applied to all data from the series of past and future HIRS instruments, this method presents the opportunity to produce a comprehensive and consistent volcanic SO2 timeseries spanning over 40 years.

Citation: Miles, G. M., Siddans, R., Grainger, R. G., Prata, A. J., Fisher, B., Krotkov, N., and Kerridge, B.: Retrieval of volcanic SO2 from HIRS/2 using optimal estimation, Atmos. Meas. Tech. Discuss.,, in review, 2017.
Georgina M. Miles et al.
Georgina M. Miles et al.


Total article views: 285 (including HTML, PDF, and XML)

HTML PDF XML Total BibTeX EndNote
195 63 27 285 11 32

Views and downloads (calculated since 06 Feb 2017)

Cumulative views and downloads (calculated since 06 Feb 2017)

Viewed (geographical distribution)

Total article views: 285 (including HTML, PDF, and XML)

Thereof 284 with geography defined and 1 with unknown origin.

Country # Views %
  • 1



Latest update: 28 Jun 2017
Publications Copernicus
Short summary
Volcanic eruptions are important in the way they perturb the climate and help us understand atmospheric processes. We show a new method to measure the SO2 released by explosive volcanic eruptions using the HIRS/2 satellite instrument, which measured atmospheric temperature and H2O. We apply the technique to the 1991 eruption of Cerro Hudson, and show it’s possible to detect SO2 with a good degree of accuracy. This method and instrument can potentially generate a climate-significant record.
Volcanic eruptions are important in the way they perturb the climate and help us understand...