Source code for pycif.plugins.transforms.complex.moist2dry.forward

import xarray as xr




def forward(
        transf,
        inout_datastore,
        controlvect,
        obsvect,
        mapper,
        di,
        df,
        mode,
        runsubdir,
        workdir,
        onlyinit=False,
        **kwargs
):
    r"""Convert a moist-air mixing ratio to a dry-air number concentration.

    Applies the conversion:

    .. math::

        C_{dry} = C_{moist}
        \cdot \underbrace{\left(1 - \beta \frac{q}{1-q}\right)
        \cdot \frac{R}{R_{dry} \cdot M} \cdot 10^{12}}_{\text{dry\_coef}}

    where:

    * :math:`\beta = (R_{vapor} - R_{dry}) / R_{vapor}` (≈ 0.378)
    * :math:`R = 8.314` J mol⁻¹ K⁻¹ (universal gas constant)
    * :math:`R_{dry} = 287.05` J kg⁻¹ K⁻¹ (dry-air gas constant)
    * :math:`M` = ``transf.molmass`` (g mol⁻¹)
    * ``q`` = specific humidity from the ``specific_humidity`` input

    In TL mode the same scalar coefficient is applied to the increment field.

    Args:
        transf (Plugin): moist2dry plugin instance (must carry ``molmass``
            in g mol⁻¹ and ``component``/``parameter`` attributes).
        inout_datastore (dict): mutable datastore; ``'inputs'`` must contain
            both the species field and the ``specific_humidity`` field.
        controlvect: unused.
        obsvect: unused.
        mapper (dict): transform mapper.
        di (datetime): sub-simulation start date.
        df (datetime): sub-simulation end date.
        mode (str): ``'fwd'`` or ``'tl'``.
        runsubdir (str): unused.
        workdir (str): unused.
        onlyinit (bool): unused.
        **kwargs: unused.
    """
    ddi = min(di, df)

    # Constants
    Rdry = 287.05
    Rvapor = 461.5
    R = 8.314462
    beta = (Rvapor - Rdry) / Rvapor

    # Converts to dry
    trid_out = (transf.component[0], transf.parameter[0])
    spec = inout_datastore["inputs"][trid_out][ddi]["spec"]
    q = inout_datastore["inputs"][
        ("specific_humidity", transf.parameter[0])][ddi]["spec"]

    dry_coef = (1 - beta * q / (1 - q)) \
               * R / Rdry / transf.molmass * 1000 * 1e9
    inout_datastore["outputs"][trid_out][ddi] = xr.Dataset(
        {"spec": spec * dry_coef})

    if mode == "tl":
        inout_datastore["outputs"][trid_out][ddi]["incr"] = \
            inout_datastore["inputs"][trid_out][ddi]["incr"] * dry_coef