Computing atmospheric absorption with AATM

Abstract

This is also a very simple program (sharing some code with dispersive) to compute the atmospheric absorption due to dry and wet components of the atmosphere.

This program will be a part of AATM-0.06 examples when this version is released. AATM is freely available here under the GPL licence (see file COPYING).

Notes on usage

There is an option to pass both the altitude of the site (–altitude) and the pressure at the ground level (–gpress) to the program. The altitude value is however only used to determine the temperature structure of the atmosphere at the site and you must also adjust the ground pressure to the correct value of the site to get sensible results.

Example usage

Example of use:

./absorption --freq 50 --ghum 1
Freq        Dry Opac                Wet Opac
50  0.119802                0.000145611

Invoking the help option:

./absorption --help
Compute absorption by the atmosphere

This program is part of AATM version 0.09
GPL license -- you have the right to the source code. See COPYING

Allowed options:
  --help                 Produce this help message
  --freq arg             Frequency at which to compute the absorption (GHz)
  --fmin arg             The starting frequency (GHz) of a frequency grid
                         (incompatible with --freq)
  --fmax arg             The end frequency (GHz) of a frequency grid
                         (incompatible with --freq)
  --fstep arg            The frequency step (GHz) of a frequency grid
                         (incompatible with --freq)
  --ghum arg             Relative humidity at ground level (percent) (currently
                         incompatible with --freq)
  --pwv arg              Precipitable water vapour in mm (incompatible with
                         --ghum)
  --altitude arg (=5000) Altitude of the site (m)
  --gpress arg (=560)    Ground level pressure (mBar)
  --gtemp arg (=270)     Ground level temperature (K)
  --wvl arg (=2)         Water vapour scale height (km)
  --tlr arg (=-5.6)      Tropospheric lapse rate (K/km)