Porous aerosol in degassing plumes of Mt. Etna and Mt. Stromboli

Abstract

Abstract. Aerosols of the volcanic degassing plumes from Mt. Etna and Mt. Stromboli were probed with in situ instruments on board the Deutsches Zentrum für Luft-und Raumfahrt research aircraft Falcon during the contrail, volcano, and cirrus experiment CONCERT in September 2011. Aerosol properties were analyzed using angular-scattering intensities and particle size distributions measured simultaneously with the Polar Nephelometer and the Forward Scattering Spectrometer probes (FSSP series 100 and 300), respectively. Aerosols of degassing plumes are characterized by low values of the asymmetry parameter (between 0.6 and 0.75); the effective diameter was within the range of 1.5-2.8 µm and the maximal diameter was lower than 20 µm. A principal component analysis applied to the Polar Nephelometer data indicates that scattering features of volcanic aerosols of different crater origins are clearly distinctive from angular-scattering intensities of cirrus and contrails. Retrievals of aerosol properties revealed that the particles were "optically spherical" and the estimated values of the real part of the refractive index are within the interval from 1.35 to 1.38. The interpretation of these results leads to the conclusion that the degassing plume aerosols were porous with air voids. Our estimates suggest that aerosol particles contained about 18 to 35 % of air voids in terms of the total volume.

Statistical analysis of contrail to cirrus evolution during the Contrail and Cirrus Experiment (CONCERT)

“…In agreement with Shcherbakov et al (2016), who characterized volcanic and cirrus using optical measurements, the PCA method has been clearly shown here to be suitable for contrail studies. The additional use of microphysical and chemical measurements can be added to the PCA method in order to improve the selection of contrail phases.…”

“…The overall objective was to reduce uncertainties on the microphysical, chemical, and radiative properties of contrails behind aircraft of different types and to improve the evaluation of contrails' impact on climate. A few CONCERT flights were also dedicated to study emissions of the Etna and Stromboli volcanos Shcherbakov et al, 2016). A few stratospheric intrusions were also observed during the flight missions.…”

The primary volcanic aerosol emission from Mt Etna: Size-resolved particles with SO2 and role in plume reactive halogen chemistry

“…Our lognormal distribution fit incurs some uncertainty in the volume peak maximum between 1-2 μm (where LOAC size bin resolution is low), and in the smallest particle mode (as the smallest size-bin is subject to greatest measurement uncertainty). Nevertheless, the distribution shows distinct supraand submicron modes, with dN/dLogD shape bearing similarity to that of Allen et al (2006) and Shcherbakov et al (2016).…”

“…Here we trace and minimise such errors. Finally, in-situ measurements of aerosol in plume >6km downwind from Mt Etna have recently also been made by aircraft, reporting R eff = 0.75-1.2 and porosity (aerosol with air-holes) at the observed low ambient temperature and humidity (Shcherbakov et al, 2016).…”

In situ measurements of angular-dependent light scattering by aerosols over the contiguous United States

“…Recently, this instrument has been modified to allow for measurements of some aerosol particles as well as ice crystals, specifically those with diameters larger than 1 µm and sufficiently higher number concentrations. The results of these measurements are presented by Shcherbakov et al (2016), who performed principal component analysis (PCA) on the light-scattering data to explore the properties of aerosols found in volcanic degassing plumes.…”