.. _Sec Empirical microwave surface emissivity:

Empirical microwave surface emissivity
#######################################

ARTS provides the TESSEM2 and TELSEM2 empirical microwave emissivity models
through the ``Tessem`` and ``Telsem`` options of
:meth:`~pyarts3.Workspace.spectral_surf_refl_agendaSet`.  Load their model data
with :class:`~pyarts3.arts.TessemNN` or
:class:`~pyarts3.arts.TelsemAtlas`, or with the corresponding workspace ASCII
reader methods.

TESSEM2
*******

TESSEM reads the following local values from ``surf_field``:

- ``"t"``: surface skin temperature [K];
- ``"wind speed"``: 10-m wind speed [m/s]; and
- ``"salinity"``: salinity [kg/kg].

Each value can use any normal :class:`~pyarts3.arts.SurfaceData`
representation, including a constant, a latitude/longitude field, or a
function.  Surface Jacobian targets for all three inputs are evaluated by
finite differences using the target perturbation.

TELSEM2
*******

TELSEM obtains its spatial variation from its monthly atlas.  It uses
``surf_field`` only for the local surface geometry and evaluates the atlas for
the ray point and local surface normal.

Surface-boundary behavior
*************************

Both agenda options return polarized specular reflectance.  Thermal emission
is supplied by the closed-surface agenda, which applies Kirchhoff consistency.