# Presentation: 531441

## 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

## Processes simulated by the ATHAM model

**Aerosol**
- Interaction of  hydrometeors and particles
- Ash aggregation (Textor et al. 2003)

**Processes simulated by the ATHAM model**

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

**Turbulence**
- Entrainment of ambient air, Prediction of turbulent energy and length scale (Oberhuber et al. 1998, Herzog et al. 2003)

**Microphysics**
- Cloud and precipitation processes, release of latent heat (Graf et al. 1999, Herzog et al. 1998, Textor 2003)

**Gas** **scavenging**
- By water and ice** **(Textor et al. 2003)

**ATHAM****: ****A****ctive ****T****racer ****H****igh Resolution ****A****tmospheric**** ****M****odel**

## 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   

**Model Setup  **** **
**Background Atmosphere**
- Vertical profiles for tropical conditions
-   		    temperature         humidity        cross wind

## ATHAM 3d simulation

- Volcanic ash in a plume of an explosive eruption

- Max-Planck-Institute for Meteorology

**Ash sizes  **                   10m                      4 mm

## ATHAM 3d simulation

- Volcanic ash in a plume of an explosive eruption

**Ash sizes  **              10m                   200 m              4 mm

- Max-Planck-Institute for Meteorology

**Notes:**
Total eruption  time was 75 minutes. Each 30 sec a picture

## ATHAM 3d simulation

- Fine ash and hydrometeors during an explosive eruption

-          fine ash                          liquid water                 ice

- Max-Planck-Institute for Meteorology