Atmospheric Chemistry Experiment (ACE) observations of aerosol in the upper troposphere and lower stratosphere from the Kasatochi volcanic eruption

Near-infrared (NIR) atmospheric extinction profile observations from the Atmospheric Chemistry Experiment (ACE) Imager and from Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (MAESTRO) are presented, illustrating the impact of the Kasatochi volcanic eruption in August 2008 on the aerosol loading of the upper troposphere and lower stratosphere in the subsequent months. In September 2008, profiles of NIR extinction show a significant increase relative to each of the previous four Septembers (2004-2007). The aerosol enhancement is observable up to 18.5 km in Northern Hemisphere NIR extinction data, and peaks at 9.5 km in the extratropics, where the extinction is similar to 8 times the normal September value. The particulate matter in the troposphere is quickly dispersed over the Northern Hemisphere during September 2008 and vanishes by the end of November 2008. An upper layer, initially in the extratropical lower stratosphere, persists through March 2009, descending with time into the troposphere where, by coagulation of sulphate aerosol, the size of the particles increases with time.