Potential of the ATHAM model for use in air traffic safety

Gerald GJ ErnstGeological Institute, University of Ghent, Gent, Belgium

Christiane Textor Lab. des Sciences du Climat et de l’Environnement,

CEA-CNRS, Gif-sur-Yvette, France

Michael HerzogDepartment of Atmospheric, Oceanic, and Space Sciences,

University of Michigan, Ann Arbor, Michigan.

Hans-F GrafDepartment of Geography, University of Cambridge,

Cambridge, UK

Josef M Oberhuber formerly at Deutsches Klima Rechenzentrum, Hamburg,

Germany

Aerosol Interaction of hydrometeors and particlesAsh aggregation (Textor et al. 2003)

Processes simulated by the ATHAM modelDynamics

Advection and thermodynamics of the gas-particle mixture (Oberhuber et al. 1998, Herzog 1998)

TurbulenceEntrainment of ambient air, Prediction of turbulent energy and length scale (Oberhuber et al. 1998, Herzog et al. 2003)

MicrophysicsCloud and precipitation processes, release of latent heat (Graf et al. 1999, Herzog et al. 1998, Textor 2003)

Gas scavengingBy water and ice (Textor et al. 2003)

ATHAM: Active Tracer High Resolution Atmospheric Model

ATHAM 3d Simulation

Max-Planck-Institute for Meteorology

Herzog M, Oberhuber JM, Graf H:A prognostic turbulence scheme for the nonhydrostatic plume model ATHAM, J ATMOS SCI 60 (22): 2783-2796 2003

•Typical plinian eruption conditions in a tropical atmosphere

•Model spin-up of 45 min

•60 min of eruption

•Model domain of 250x200x50 km3, 127x107x127 grid points

•Stretched grid with 100m resolution at the volcano and some kilometers at the model

boundaries

•Cloud microphysics with water and ice, precipitation development

•No ash aggregation

Visualisation:M. Böttinger Deutsches Klima Rechenzentrum

Model Setup

Conditions at the eruption column base

•Mountain height 2500m

•Width of base 300m

•Temperature 1073 K

•Gas mass fraction 6 % by mass

•Water vapor mass fraction of tot. gas 50% by mass

•Bulk density of the gas particle mixture~3.1 kg/m3

•Vertical velocity at eruption column base 250 m/s

•Mass eruption rate ~5.55 107 kg/s

Model Setup

Particle properties

•Particle density 2000 kg/m3

•Three particle classes 1/3 by mass each

•Particle sizes [m] 10 200 4000

•Terminal fall velocity at 1bar [m/sec] 0.024 3.2 15.2

Model Setup

Background AtmosphereVertical profiles for tropical conditions

temperature humidity cross wind

Volcanic ash in a plume of an explosive eruptionA

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Ash sizes 10m 4 mm

Volcanic ash in a plume of an explosive eruption

Ash sizes 10m 200 m 4 mm

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Fine ash and hydrometeors during an explosive eruption

fine ash liquid water ice

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