The gases.def Input File

Note: the gases.def file is used by the Generic PCM.

A typical gases.def file for the Earth case:

# gases
3
N2_
CO2
H2O
0.999611900E+00
0.375999962E-03
-1


# First line is number of gases
# Followed by gas names (always 3 characters)
# and then mixing ratios.
# mixing ratio -1 means the gas is variable.

• Note that the first line of the file is actually not read
• The second line must contain the number of gases (here 3) accounted for
• Then come the gas names (always 3 characters!), one per line. Here N2_, CO2 and H2O
• Followed by the gas volume mixing ratios (mol/mol_of_atm), if the gas concentration is assumed to be constant, or -1 if it is variable. In the example given above N2 and CO2 will be taken as having "constant" mixing ratios of respectively 0.9996119 and 0.375999962E-03, whereas H2O will be variable. By "constant" is mean the proportion wrt to 1.0 (the normalized amount of the sum of all tracers) i.e. in the example above, since 0.9996119+0.375999962E-03=0.999987899962 these exact values are for when the volume mixing ratio of H2O is 1.21e-5 mol/mol.

Another example of a gases.def file, from the Early Mars case, where only two gases are considered, CO2 and H2O, with only H2O as variable:

# gases
2
CO2
H2O
1.0
-1

# First line is number of gases
# Followed by gas names (always 3 characters)
# and then mixing ratios.
# mixing ratio -1 means the gas is variable.

Technical aspects

In the code this file is read by the su_gases routine, which handles only preset possibilities (gas names).