Volcanic ash from Iceland over Munich: mass concentration retrieved from ground-based remote sensing measurements

Abstract. Volcanic ash plumes, emitted by the Eyjafjallajokull volcano (Iceland) in spring 2010, were observed by the lidar systems MULIS and POLIS in Maisach (near Munich, Germany), and by a CIMEL Sun photometer and a JenOptik ceilometer in Munich. We retrieve mass concentrations of volcanic ash from the lidar measurements; spectral optical properties, i.e. extinction coefficients, backscatter coefficients, and linear depolarization ratios, are used as input for an inversion. The inversion algorithm searches for model aerosol ensembles with optical properties that agree with the measured values within their uncertainty ranges. The non-sphericity of ash particles is considered by assuming spheroids. Optical particle properties are calculated using the T-matrix method supplemented by the geometric optics approach. The lidar inversion is applied to observations of the pure volcanic ash plume in the morning of 17 April 2010. We find 1.45 g m −2 for the ratio between the mass concentration and the extinction coefficient at λ = 532 nm, assuming an ash density of 2.6 g cm −3 . The uncertainty range for this ratio is from 0.87 g m −2 to 2.32 g m −2 . At the peak of the ash concentration over Maisach the extinction coefficient at λ = 532 nm was 0.75 km −1 (1-h-average), which corresponds to a maximum mass concentration of 1.1 mg m −3 (0.65 to 1.8 mg m −3 ). Model calculations show that particle backscatter at our lidar wavelengths (λ ≤ 1064 nm), and thus the lidar retrieval, is hardly sensitive to large particles ( r ≳ 3 μm); large particles, however, may contain significant amounts of mass. Therefore, as an independent cross check of the lidar retrieval and to investigate the presence of large particles in more detail, we model ratios of sky radiances in the aureole of the Sun and compare them to measurements of the CIMEL. These ratios are sensitive to particles up to r ≈ 10 μm. This approach confirms the mass concentrations from the lidar retrieval. We conclude that synergistic utilization of high quality lidar and Sun photometer data, in combination with realistic aerosol models, is recommended for improving ash mass concentration retrievals.

[1]  A. Ansmann,et al.  Independent measurement of extinction and backscatter profiles in cirrus clouds by using a combined Raman elastic-backscatter lidar. , 1992, Applied optics.

[2]  Hester Volten,et al.  Scattering matrices of volcanic ash particles of Mount St. Helens, Redoubt, and Mount Spurr Volcanoes , 2004 .

[3]  Bernhard Mayer,et al.  Atmospheric Chemistry and Physics Technical Note: the Libradtran Software Package for Radiative Transfer Calculations – Description and Examples of Use , 2022 .

[4]  Bayesian assessment of uncertainty in aerosol size distributions and index of refraction retrieved from multiwavelength lidar measurements. , 2008, Applied optics.

[5]  P. Ginoux.  Effects of nonsphericity on mineral dust modeling , 2003 .

[6]  Albert Tarantola,et al.  Probabilistic Approach to Inverse Problems , 2002 .

[7]  M. Mishchenko,et al.  Modeling phase functions for dustlike tropospheric aerosols using a shape mixture of randomly oriented polydisperse spheroids , 1997 .

[8]  H. Jäger.  Long‐term record of lidar observations of the stratospheric aerosol layer at Garmisch‐Partenkirchen , 2005 .

[9]  H. V. Hulst.  Light Scattering by Small Particles , 1957 .

[10]  H. Quenzel,et al.  Information content of aerosol optical properties with respect to their size distribution. , 1982, Applied optics.

[11]  J. Hovenier,et al.  Depolarization of light backscattered by randomly oriented nonspherical particles. , 1995, Optics letters.

[12]  B. Mayer.  Radiative transfer in the cloudy atmosphere , 2009 .

[13]  David C. Pieri,et al.  Analyses of in‐situ airborne volcanic ash from the February 2000 eruption of Hekla Volcano, Iceland , 2002 .

[14]  A. Wiedensohler,et al.  Size distribution, mass concentration, chemical and mineralogical composition and derived optical parameters of the boundary layer aerosol at Tinfou, Morocco, during SAMUM 2006 , 2009 .

[15]  A. Smirnov,et al.  AERONET-a federated instrument network and data archive for aerosol Characterization , 1998 .

[16]  V. Freudenthaler,et al.  The 16 April 2010 major volcanic ash plume over central Europe: EARLINET lidar and AERONET photometer observations at Leipzig and Munich, Germany , 2010 .

[17]  Klaus Gierens,et al.  Effective Radius of Ice Particles in Cirrus and Contrails , 2011 .

[18]  A. Ansmann,et al.  Volcanic aerosol layers observed with multiwavelength Raman lidar over central Europe in 2008–2009 , 2010 .

[19]  Peter W. Webley,et al.  Volcanic ash plume identification using polarization lidar: Augustine eruption, Alaska , 2007 .

[20]  Ulrich Bundke,et al.  Chemical composition and complex refractive index of Saharan Mineral Dust at Izaña, Tenerife (Spain) derived by electron microscopy , 2007 .

[21]  Larry D. Travis,et al.  Capabilities and limitations of a current FORTRAN implementation of the T-matrix method for randomly oriented, rotationally symmetric scatterers , 1998 .

[22]  Alfons G. Hoekstra,et al.  The discrete dipole approximation for simulation of light scattering by particles much larger than the wavelength , 2007 .

[23]  Volcanology: Out of the ashes , 2010, Nature.

[24]  M. Mishchenko,et al.  Applicability of regular particle shapes in light scattering calculations for atmospheric ice particles. , 1996, Applied optics.

[25]  Ping Yang,et al.  Light scattering by hexagonal ice crystals: solutions by a ray-by-ray integration algorithm , 1997 .

[26]  Geoffrey Y. Gardner,et al.  Simulation of natural scenes using textured quadric surfaces , 1984, SIGGRAPH.

[27]  M. Esselborn,et al.  Numerical simulations of optical properties of Saharan dust aerosols with emphasis on lidar applications , 2009 .

[28]  F. G. Fernald.  Analysis of atmospheric lidar observations: some comments. , 1984, Applied optics.

[29]  W. Steinbrecht,et al.  The Eyjafjallajökull eruption in April 2010 – detection of volcanic plume using in-situ measurements, ozone sondes and lidar-ceilometer profiles , 2010 .

[30]  V. Freudenthaler,et al.  Depolarization ratio profiling at several wavelengths in pure Saharan dust during SAMUM 2006 , 2009 .

[31]  Ralf Gertisser,et al.  Eyjafjallajökull volcano causes widespread disruption to European air traffic , 2010 .

[32]  F. S. Marvin.  Out of the Ashes , 1942, Nature.

[33]  V. Freudenthaler,et al.  Characterization of the Eyjafjallajökull ash-plume: Potential of lidar remote sensing , 2012 .

[34]  U. Schumann,et al.  Airborne observations of the Eyjafjalla volcano ash cloud over Europe during air space closure in April and May 2010 , 2010 .

[35]  Valery Adzhiev,et al.  HyperFun project: a framework for collaborative multidimensional F-rep modeling , 2000 .

[36]  A. Tarantola.  Popper, Bayes and the inverse problem , 2006 .

[37]  E. Patterson,et al.  Optical properties of the ash from El Chichon volcano , 1983 .

[38]  P. Koepke,et al.  Optical Properties of Aerosols and Clouds: The Software Package OPAC , 1998 .

[39]  Josef Gasteiger,et al.  Characterization of the Eyjafjallajökull ash-plume by means of lidar measurements over the Munich EARLINET-site , 2010, Remote Sensing.

[40]  T. Nakajima,et al.  Retrieval of the optical properties of aerosols from aureole and extinction data. , 1983, Applied optics.

[41]  H. Quenzel,et al.  Information content of multispectral lidar measurements with respect to the aerosol size distribution. , 1985, Applied optics.

[42]  Jean-François Léon,et al.  Application of spheroid models to account for aerosol particle nonsphericity in remote sensing of desert dust , 2006 .