Articles | Volume 9, issue 5
Research article
12 May 2016
Research article |  | 12 May 2016

Ash and ice clouds during the Mt Kelud February 2014 eruption as interpreted from IASI and AVHRR/3 observations

Arve Kylling

Abstract. During the Mt Kelud February 2014 eruption the ash cloud was detectable on 13–14 February in the infrared with the reverse absorption technique by, for example, the Advanced Very High Resolution Radiometer (AVHRR/3). The Infrared Atmospheric Sounding Interferometer (IASI) observed the ash cloud also on 15 February when AVHRR did not detect any ash signal. The differences between ash detection with AVHRR/3 and IASI are discussed along with the reasons for the differences, supported by radiative transfer modelling. The effect of concurrent ice clouds on the ash detection and the ash signal in the IASI measurements is demonstrated. Specifically, a radiative transfer model is used to simulate IASI spectra with ash-only, with ice cloud only and with both ash and ice clouds. It is shown that modelled IASI spectra with ash and ice clouds reproduce the measured IASI spectra better than ash-only- or ice-only-modelled spectra. The ash and ice modelled spectra that best reproduce the IASI spectra contain about a factor of 12 less ash than the ash-only spectra that come closest to reproducing the measured spectra.

Short summary
During volcanic eruptions the presence of ice clouds may affect the volcanic ash signal in infrared satellite measurements. By comparison of measured infrared spectra with spectra from a radiative transfer model including both ash and ice clouds, it is shown that during the Mt Kelud February 2014 eruption, both ash and ice clouds were present simultaneously. The presence of ice clouds lowers the estimated amount of volcanic ash in the atmosphere.