Simplified Prognostic Aerosol Module Prog2DAero#

ICON contains a simplified, computationally cheap aerosol module Prog2DAero. The additional cost in a global simulation is typically below 1%. The idea is to account for the main causes of variability in atmospheric aerosol concentrations not reflected in climatological values. It is based on the Tegen climatological aerosol which is used for operational numerical weather prediction with ICON. Severeal design choices for Prog2DAero were made based on characteristics of this climatology (see here). Prog2DAero makes use of the vertically integrated optical depth of the five species Sea Salt, Soil Dust, Sulfate, Organic Carbon and Black Carbon as prognostic variable and adds the following process descriptions:

  • Horizontal transport using vertically averaged wind fields

  • Artificial diffusion to account for vertical wind shear

  • Emissions based on physical parameterizations for natural aerosol species (sea salt, soil dust)

  • Emissions based on datasets for anthropogenic and wildfire emissions

  • Source term for Sulfate to account for nucleation from the gas phase

  • Wet deposition due to grid-scale and convective processes

  • Relaxation approach to account for other sink terms (sedimentation, dry deposition)

The prognostic equation for aerosol species j can be written as

\[\frac{\partial \psi_j}{\partial t} = \overline{v_{H,j}}\nabla\psi_j + c_{diff,j} \nabla^2 \psi_j + S_{e,j} + S_{w,j} +\frac{\psi_{clim,j}-\psi_j}{\tau_{clim,j}}\]

where the right hand side terms are advection, artificial diffusion, source terms, sink terms and relaxation. \(\psi_j\) denotes the vertically integrated optical depth, \(\overline{v_{H,j}}\) the vertically averaged horizontal wind, \(c_{diff,j}\) a diffusion coefficient, \(S_{e,j}\) source terms (emission), \(S_{w,j}\) sink terms (washout), \(\psi_{clim,j}\) the climatological value of vertically integrated optical depth and \(\tau_{clim,j}\) a relaxation time scale.

Parts of Prog2DAero can be activated individually. By chosing the namelist parameter i2daero_dust =1, the simplified prognostic description for soil dust can be activated. Likewise, i2daero_seas =1 activates sea salt. The three species Sulfate, Organic Carbon and Black Carbon can be activated by i2daero_anthro =1. In addition, emissions from wild fires can be added to these species using the namelist option i2daero_fire.

Combination with ICON-ART#

Since the more sophisticated aerosol from ICON-ART uses Tegen climatological aerosol complementary for species that are not considered by the ICON-ART setup, Prog2DAero can be used complementary to ICON-ART in a similar way. For example by using natural aerosol (Mineral Dust, Sea Salt) from ICON-ART and anthropogenic and wildfire species (Sulfate, Organic Carbon, Black Carbon) from Prog2DAero.

Glossary of Namelist Parameters#

Operational NWP setting marked by

i2daero_dust#

(nwp_phy_nml) Activate soil dust from Prog2DAero 0: deactivated, 1: activated

i2daero_seas#

(nwp_phy_nml) Activate sea salt from Prog2DAero 0: deactivated, 1: activated

i2daero_anthro#

(nwp_phy_nml) Activate anthropogenic aerosol (Sulfate, Organic Carbon and Black Carbon) from Prog2DAero 0: deactivated, 1: activated requires enable_edgar during ExtPar dataset generation with Zonda

i2daero_fire#

(nwp_phy_nml) Activate wild fire aerosol (Sulfate, Organic Carbon and Black Carbon) from Prog2DAero 0: deactivated, 1: Read from file 2: Seasonal climatology

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