Aerosol model SALSA

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Overview

The aerosol module SALSA (Kokkola et al., 2008) embedded in PALM can be used to simulate the aerosol particle concentrations, size distributions and chemical compositions. In SALSA, the aerosol size distribution is represented as a discrete set of size bins (by default 10 bins). The number n_i (m^-3) and mass concentration m_c,i (kg m^-3) of each size bin i and chemical component c are the model prognostic variables. Currently, the following chemical components can be included: sulphuric acid (H2SO4), organic carbon (OC), black carbon (BC), nitric acid (HNO3), ammonium (NH3), sea salt, dust and water (H2O). Furthermore, the gaseous concentrations of H2SO4, HNO3, NH3 and semi- and non-volatile organics (OCNV and OCSV) are also default prognostic variables. The aerosol dynamic processes included are coagulation, condensation of H2SO4, organics and water vapour, dissolutional growth by HNO3 and NH3, nucleation and dry deposition on horizontal and vertical surfaces and resolved vegetation.

SALSA can be coupled with the chemistry module. In that case, the five gaseous compounds (H2SO4, HNO3, NH3, OCNV and OCSV) will be imported to SALSA from the chemistry module and should thus be included in the chemical mechanism applied.

SALSA is enabled by adding the NAMELIST salsa_parameters with appropriate parameters to the INPUT parameter file (<run_identifier>_p3d). Available parameters are listed below.

SALSA runs with the default parameter values. By default, the aerosol particle and gaseous concentrations are initially constant everywhere (isdtyp = 0 and igctyp = 0). A minimum set of input parameters to be applied when this initialisation type is used, is:

• dpg, n_lognorm and sigmag to describe the initial aerosol size distribution plus

• listspec, mass_fracs_a to include chemical compounds plus

• H2SO4_init, HNO3_init, NH3_init, OCNV_init, OCSV_init to set the initial concentrations of gaseous compounds plus

• nlcnd, nlcndgas, nlcndgash2oae, nlcoag, nldepo, nldepo_topo, nldepo_vege, nsnucl to switch on aerosol dynamic processes.

Alternatively, the initial aerosol particle concentrations, size distributions and chemical compositions and gaseous concentrations as well as emission/source information of aerosol particles and gases can be provided in NetCDF input files <run_identifier>_salsa (for aerosol particles) and <run_identifier>_chemistry (for gaseous compounds). Aerosol particle emissions can be provided applying three levels of detail (LOD): parametrised (LOD1, units kg m^-2 s^-1) or detailed (LOD2, units m^-2 s^-1) 2-dimensional surface fluxes, or 3-dimensional sources (LOD3, units m^-3 s^-1). Gaseous emissions, instead, should currently be specified as gas-specific surface fluxes (LOD2) if the chemistry module is not applied. The time dependency of the aerosol emissions has not yet been implemented. Example files for each LOD is provided in the attached test_salsa example set-up.

The attached test_salsa example includes:

• test_salsa_p3d: ASCII parameter file
• test_salsa_static: NetCDF static-information file with topography information (so-called static driver)
• test_salsa_chemistry: a NetCDF information file including the initial vertical profiles and surface emissions of gaseous compounds (H2SO4, HNO3, NH3, OCNV and OCSV)
• LODX_test_salsa_salsa: a NetCDF information including the initial vertical profiles and emissions of aerosol particles for each level of detail X = 1, 2, 3. NOTE! Copy the chosen file to test_salsa_salsa

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SALSA Parameters