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Workspace Method surfaceTelsem

Description

Compute surface emissivities using the TELSEM 2 model.

This method uses second version of the TELSEM model for calculating
land surface emissivities (F. Aires et al, "A Tool to Estimate 
 Land‐Surface Emissivities at Microwave frequencies (TELSEM) for use
 in numerical weather prediction" Quarterly Journal of the Royal
Meteorological Society, vol. 137, (656), pp. 690-699, 2011.)
This methods computes land surface emissivities for a given pencil beam
using a given TELSEM2 atlas.
The input must satisfy the following conditions, otherwise an error is thrown:
 - The input frequencies (f_grid) must be within the range [5 GHz, 900 GHz]
 - The skin temperature (surface_skin_t) must be within the range
   [180 K, 360 K]

A TELSEM atlas contains only suface emissivities for locations that are
classified as land. By default this WSM will throw an error if the
pencil beam hits the surface at a position that is not contained in the
given atlas.

The above behavior can be avoided by setting *d_max* to a positive value.
This enables nearest neighbor interpolation, which assigns the emissivities
of the nearest found cell in the atlas to the given position. In this case,
an error is only thrown if the distance of the found neighbor is higher
than the provided value of *d_max.

You can limit the final reflectivity applied by setting *r_min* and *r_max*.

To extract a land-sea mask from a given telsem atlas see the WSM
telsemSurfaceTypeLandSea.

Authors: Simon Pfreundschuh

Synopsis

surfaceTelsem(

surface_los, surface_rmatrix, surface_emission, atmosphere_dim, stokes_dim, f_grid, lat_grid, lat_true, lon_true, rtp_pos, rtp_los, surface_skin_t, atlas, r_min, r_max, d_max )

Variables

OUT	surface_los	(Matrix)	Downwelling radiation directions to consider in surface reflection.
OUT	surface_rmatrix	(Tensor4)	The reflection coefficients for the directions given by surface_los to the direction of interest.
OUT	surface_emission	(Matrix)	The emission from the surface.
IN	atmosphere_dim	(Index)	The atmospheric dimensionality (1-3).
IN	stokes_dim	(Index)	The dimensionality of the Stokes vector (1-4).
IN	f_grid	(Vector)	The frequency grid for monochromatic pencil beam calculations.
IN	lat_grid	(Vector)	The latitude grid.
IN	lat_true	(Vector)	Latitudinal geolocation for 1D and 2D data.
IN	lon_true	(Vector)	Longitudinal geolocation for 1D and 2D data.
IN	rtp_pos	(Vector)	Position of a radiative transfer point.
IN	rtp_los	(Vector)	Line-of-sight at a radiative transfer point.
IN	surface_skin_t	(Numeric)	Surface skin temperature.
GIN	atlas	(TelsemAtlas)	The Telsem atlas to use for the emissivity calculation.
GIN	r_min	(Numeric, Default: 0)	Minimum allowed value for reflectivity to apply.
GIN	r_max	(Numeric, Default: 1)	Maximum allowed value for reflectivity to apply.
GIN	d_max	(Numeric, Default: -1.0)	Maximum allowed distance in meters for nearest neighbor interpolation in meters. Set to a negative value or zero to disable interpolation.