RRTMGP: gas concentrations

Class ty_gas_concs from module mo_gas_concentrations in the RRTMGP library is the means for specifying gas concentrations to ty_gas_optics%gas_optics. The class has four user-facing procedures. The following examples assume the declaration type(ty_gas_concs) :: gas_concs

Specifying gas concentrations

  function set_vmr(name, value) result(error_msg)
    character(len=*),    intent(in   ) :: name
    real(wp), ...        intent(in   ) :: value
    character(len=128)                 :: error_msg

specifies the absolute volume mixing ratio for the named gas. The routine is invoked as e.g.err_msg = gas_concs%set_vmr("co2", 280._wpE-6). Gas names are normally the chemical formula.

Values may be specified as scalars, one-dimensional profiles assumed to apply layer-by-layer to all columns, or as a 2D field dimensioned (columns, layers). The number of columns is set the first time a 1D or 2D field is supplied; the number columns is determined from the first 2D field.

Extracting a subset of columns

  function get_subset(start, n, subset) result(error_msg)
    integer,                  intent(in   ) :: start, n
    class(ty_gas_concs),      intent(inout) :: subset
    character(len=128)                      :: error_msg

extracts columns start to start+n-1 from the class. Example: err_msg = gas_concs%get_subset(2, n, gas_conc_subset)

Misc.

call gas_concs%reset() will return variable gas_concs to an un-initialized state. This is useful if, for example, the problem size has changed since concentrations were last specified.

gas_concs%get_vmr() is used within ty_gas_optics%gas_optics() to extract the gas concentrations.