Linear Chemistry Module

The Linear Chemistry Module (LCM) is based on the initial work of Henne et al. who developed the FLEXPART-CTM model from FLEXPART 8, and was first described in Groot Zwaaftink et al.. This model was an extension of the domain-filling capability of FLEXPART and added the possibility to initialise particles’ mixing ratio from pre-defined fields, account for the influence of surface fluxes and simple linear chemistry on the particles’ mass, and sample the particle mixing ratios at user-defined receptor locations.

How to run LCM

To run the LCM the following OPTIONS files are used and need to be edited (see also the Appendix for example OPTIONS files):

  1. COMMAND: choose the following options:

    • LDIRECT= 1 (forward simulation)
    • MDOMAINFILL = 1 (domain-filling mode)
    • IND_SOURCE = 1 (releases units of mass)
    • IND_RECEPTOR = 1 (receptor units of mass)
    • LCMOUTPUT = 1 (uses the LCM initialization and output formats)

  2. RELEASES: specify the following:

    • NSPEC: number of species including the mandatory species AIRTRACER
    • SPECNUM_REL: species number in the directory SPECIES (note AIRTRACER must be the first species)
    • LON1: left longitude of release box for global domain
    • LON2: right longitude of release box for global domain
    • LAT1: lower latitude of release box for global domain
    • LAT2: upper latitude of release box for global domain
    • PARTS: total number of particles to be used

  3. INITCONC: specifies input for initializing the mixing ratios

  4. OUTGRID: specifies the domain and vertical levels for the gridded output

  5. REAGENTS (optional): specifies chemical reagents for reactions (the corresponding rate constants are given in the SPECIES files)

  6. RECEPTORS (optional): specifies the locations and times of receptors where mixing ratios should be output.

  7. SATELLITES (optional): specifies paths and input file names of satellite retrievals for which mixing ratios should be output. Input files need to be generated from a satellite pre-processor, prep_satellite, and can be created using software obtainable from flexinvertplus.