ARTS built-in documentation server
Workspace Method FastemStandAlone
Description
Stand-alone usage of FASTEM.
FASTEM is a parameterisation of the emissivity of water surfaces
including the impact of waves, salinity and non-specular effects.
This is more or less direct interface to FASTEM, but slightly
adopted to fit with ARTS. The unit of frequency and salinity
differ, and this version is "vectorised" in frequency.
The output is four emissivity and reflectivity values for each
frequency. These values are defined in Eq. 13 of "An Improved
Fast Microwave Water Emissivity Model" by Liu, Weng and English,
I3TRGS, 2011. Note that emissivity and reflectivity do not add up
to 1, which is the way FASTEM compensates for non-specular effects.
There is an error if any frequency is above 250 GHz, or if the skin
temperature is below 260 K. If the skin temperature is below 270 K,
it is adjusted to 270 K.
FASTEM returns unphysical values for propagation close to the
horizon, here emissivity and reflectivity can be outside [0,1].
If either emissivity or reflectivity is below/above 0/1, it is
set to 0/1, and the other value is set to 1/0. That is, e+r=1
is enforced. These problems start about 15 degrees from the horizon.
Authors: Oliver Lemke, Patrick Eriksson
Synopsis
| FastemStandAlone( | emissivity, reflectivity, f_grid, surface_skin_t, za, salinity, wind_speed, rel_aa, transmittance, fastem_version ) |
Variables
| GOUT | emissivity | (Matrix) | Emission values. One row for each frequency. See above. |
| GOUT | reflectivity | (Matrix) | Reflectivity values. One row for each frequency. See above. |
| IN | f_grid | (Vector) | The frequency grid for monochromatic pencil beam calculations. |
| IN | surface_skin_t | (Numeric) | Surface skin temperature. |
| GIN | za | (Numeric) | Zenith angle of line-of-sigh, 90 to 180 deg. |
| GIN | salinity | (Numeric, Default: 0.035) | Salinity, 0-1. That is, 3% is given as 0.03. |
| GIN | wind_speed | (Numeric) | Wind speed. |
| GIN | rel_aa | (Numeric) | Azimuth angle between wind direction and line-of-sight. This angle is measured clockwise from north, i.e. E=90deg. |
| GIN | transmittance | (Vector) | The transmission of the atmosphere, along the propagation path of the downwelling radiation. One value per frequency. |
| GIN | fastem_version | (Index, Default: 6) | The version of FASTEM to use. |