Contrail Module

This webpage describes how to run the contrail module. More information about the scientific background can be found here.

Configuration File

Warning

It is currently not possible to calculate the contrail climate impact for multiple different aircraft within the same emission inventory. This is the subject of ongoing work.

In the species section, the following need to be selected:

[species]
inv = ["...", "distance"]
out = ["...", "cont"]

This tells OpenAirClim that the “distance” variable in the input emission inventories is to be used and that the contrail climate impact should be calculated.

The emission inventories should of course be defined as normal. In addition, the variable rel_to_base need to be defined: if false, then only the emission inventories in files are considered; if true, then the base emission inventories are also used. The base emission inventories can be used to simulate background air traffic. For example, if the contrail climate impact of a single aircraft design is to be calculated, then the base emission inventories could be the remaining air traffic. This is important because the contrail climate impact is highly non-linear.

So, for example, the following would be the setup if the contrail climate impact of an A320 with background air traffic were to be simulated:

[inventories]
dir = "path/to/inventories"
files = [
    "a320_inv_2020.nc",
    "...",
    "a320_inv_2045.nc",
    "a320_inv_2050.nc",
]
rel_to_base = true
base.dir = "path/to/inventories"
base.files = [
    "bg_inv_2020.nc",
    "bg_inv_2050.nc",
]

The requirement is that the emission inventories and base emission inventories must align at the first and last year, in this case in 2020 and 2050. OpenAirClim features a built-in interpolator for base emission inventories. The above configuration will thus work without issue - OpenAirClim will interpolate the base emission inventories onto the years defined by the A320 emission inventories.

In the response options, the following values are relevant for the contrail module:

[responses]
dir = "path/to/responses"
cont.response_grid = "cont"  # should not be changed
cont.resp.file = "resp_cont_lf.nc"
# cont.method = "Megill_2025"  # this method is chosen by default

A conventional OpenAirClim configuration uses the above values. The file resp_cont.nc can be used in conjuction with cont.method="AirClim" to simulate the AirClim contrail module for testing. However, this is not generally recommended outside of unit testing, because 1) the simulated AirClim module is restrictive in its input and 2) the OpenAirClim contrail module includes many improvements.

The contrail efficacy can be adapted using:

[temperature]
cont.efficacy = 0.59

Finally, the aircraft and three variables G_250, eff_fac and PMrel must be defined. From OpenAirClim v0.11.0 onwards, the aircraft types are active. In principle, any aircraft identifier (except "TOTAL") can be selected, except that the first character must be a letter to comply with python. These identifiers must match with those present in the input emission inventories (see the next section). If no identifiers are present in the emission inventories, please use types = ["DEFAULT"].

Warning

It is currently not possible to calculate the contrail climate impact of multiple different aircraft within the same emission inventory. If multiple different types are given whilst simultaneously including species.out = ["...", "cont"], OpenAirClim will produce an error.

[aircraft]
types = ["A320", "B737"]
A320.G_250 = 1.90
A320.eff_fac = 1.1
A320.PMrel = 1.0
B737.G_250 = 1.85
B737.eff_fac = 1.05
B737.PMrel = 0.8

Note

In the future, it will be possible to define these values in a separate csv file.

Emission Inventories

To calculate a contrail climate impact, the input emission inventories must include a distance (float) variable. This corresponds with the total yearly flown distance (km).

Optionally, the emission inventories can have a variable ac (str), corresponding to the aircraft identifiers defined in the configuration file. If this variable is defined, all identifiers (also in the base emission inventories) must be included in the configuration file. If this variable is not present, OpenAirClim will use the identifier DEFAULT, which must be defined in the configuration file.