MSFC: Moist Surface-Level Modules

    All variables found within the MSFC module are "moist" variables (i.e. explicitly
    affected by water and/or convection), and are considered to be "surface-level"
    variables by ECMWF reanalysis. This means that they are variables defined only over the
    "surface", which is along the surface orography.

    To select this module in erainitialize, use:
        - erainitialize(modID="msfc")

    Examples of MSFC variables are:
        - Precipitation (Total, Convective and Large-Scale Components)
        - Total Column Water (Total, and Vapour Components)
        - Convective Available Potential Energy (CAPE)
        - Surface (2m) Dewpoint Temperature

    In ERA5, MSFC variables are identified as:
        - reanalysis-era5-single-levels

    In ERA-Interim, MSFC variables are identified as:
        - levtype: sfc
        - It is worth noting that in ERA-Interim, precipitation and CAPE are considered to
          be *forecast* components and are thus treated slightly differently compared to
          other variables.  This is transparent to the user in ClimateERA.jl

    Note: If you are interested in collaborating to add other variables this feature,
    please contact me (Nathanael), and/or create a pull request.
