ARTS built-in documentation server

Workspace Method surfaceLambertianSimple

Description

Creates variables to mimic a Lambertian surface.

A Lambertian surface can be characterised solely by its
reflectivity, here taken from surface_scalar_reflectivity.

The down-welling radiation field is estimated by making calculations
for *lambertian_nza* directions. The range of zenith angles ([0,90])
is divided in an equidistant manner for 1D. For 2D and 3D see below.
The values for surface_rmatrix are assuming a constant radiance
over each zenith angle range. See AUG.

Default is to select the zenith angles for sensor_los to be placed
centrally in the grid ranges. For example, if *lambertian_nza* is set
to 9, down-welling radiation will be calculated for zenith angles = 
5, 15, ..., 85. The position of these angles can be shifted by
*za_pos*. This variable specifies the fractional distance inside the
ranges. For example, a *za_pos* of 0.7 (np still 9) gives the angles
7, 17, ..., 87.

Only upper-left diagonal element of the surface_rmatrix is
non-zero. That is, the upwelling radiation is always unpolarised.

Local thermodynamic equilibrium is assumed, which corresponds to
that the reflection and emission coefficients "add up to 1".

For 2D and 3D, the down-welling directions are placed along the
the viewing direction, e.g. for 3D the azimuth angle is kept constant.
In 2D and 3D surface topography can exist, and to avoid getting views
going directly into the surface, angels are not distributed over 90 deg,
but 90-abs(surface_normal[0]).

Authors: Patrick Eriksson

Synopsis

Variables