Sarychev Peak (Kurile Is) Eruption

Above: Astronaut photo from ISS, June 14, 2009

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The eruption of Sarychev Peak (Kurile Islands) in mid-June 2009 produced a large stratospheric sulfur dioxide (SO₂) cloud that spread rapidly eastward in strong jet stream winds. The volcanic cloud impacted the busy North Pacific air corridor and many trans-Pacific flights were rerouted or cancelled.

Beginning in May 2007, some Ozone Monitoring Instrument (OMI) cross-track scenes began to show radiance anomalies, impacting the quality of the level 1B and level 2 data products. These anomalies have since expanded and currently affect ~25% of OMI cross-track scenes, creating data gaps in OMI level 2 data products.

Synergy between A-Train instruments permits 'filling-in' of the OMI data gaps with near-coincident SO₂ retrievals from the AIRS instrument on Aqua, ~8 minutes ahead of Aura. Following the A-Train reconfiguration completed in May 2008, Aura and Aqua nadir are very close. Neither OMI (due to the row anomaly) or AIRS (due to its narrower swath) provided complete coverage of the Sarychev Peak eruption cloud, but by merging SO₂ data from the two sensors contiguous coverage is achieved. Thus accurate measurements of SO₂ loading by large volcanic eruptions can still be made.

The Sarychev Peak eruption was the second significant SO₂ injection (~1 Tg SO₂) into the Northern Hemisphere (NH) stratosphere in a year, following the eruption of Kasatochi volcano (Aleutian Islands) in August 2008 (~1.4 Tg SO₂). Due to these recent eruptions, stratospheric sulfate aerosol concentrations in the NH may be elevated compared to recent years, with possible impacts on atmospheric chemistry and radiation. The timing of the Sarychev Peak eruption close to the summer solstice is significant as it increases the radiative (cooling) effect of the sulfate aerosol.

Note that there are some differences in the SO₂ columns retrieved by OMI and AIRS which may be reduced by 'tuning' the retrievals using accurate information on SO₂ cloud altitude and vertical extent.

It might also be possible to combine aerosol measurements (e.g., volcanic ash loading) from OMI and AIRS in a similar way.

• 2nd large NH stratospheric SO₂ injection (>1 Tg) in a year, after the August 2008 Kasatochi eruption (Aleutian Is)
• Timing near summer solstice increases aerosol radiative (cooling) effect.
• Current OMI row anomaly creates data gaps in large volcanic eruption clouds
• A-Train synergy compensates for lost data and improves SO2 loading measurements

10.2009