Revision as of 10:02, 12 February 2025

As of February 2025, we have now implemented a new continuum database in the Generic PCM. The continuum files are provided here (please contact Martin if you have any suggestion, question, new additions you want to make): https://web.lmd.jussieu.fr/~lmdz/planets/LMDZ.GENERIC/datagcm/continuum_data/

File format and location

The files are stored here: https://web.lmd.jussieu.fr/~lmdz/planets/LMDZ.GENERIC/datagcm/continuum_data/

The first line of the file (header) list the grid of temperatures. For the next lines, the first column corresponds to the wavenumber (in cm-1), then the absorption coefficient at the first temperature, etc.

Note : We have stored all the ancient continuum files (e.g., HITRAN format) in the https://web.lmd.jussieu.fr/~lmdz/planets/LMDZ.GENERIC/datagcm/continuum_data/pre-2025_continua/ directory.

Units

The continuum absorption a_normXY units of the tables is cm-1 amagat-2. This is a standard units for continuum absorption.

The absorption coefficient a_XY (m-1) </math> for molecules X and Y can then be computed from the following equation:

 a_XY = 100.0 * a_normXY * amagat_X * amagat_Y ! 

 with amagat_X = (273.15/T)*(P_X/101325.0)
 with amagat_Y = (273.15/T)*(P_Y/101325.0)

with T the temperature (in K), P_X and P_Y the partial pressure of the molecules X and Y (in Pascal units).

Note : The HITRAN continuum files are in cm^5 molecule-2 units. You can convert HITRAN continuum data into cm-1 amagat-2 by dividing them by \(1.385 \times 10^{-39}\)

List of continua in the database

Below we provide the list of continua included in the database, with some details on how they were computed.

CO2-CO2

CO2-CO2 CIA new database fev2025.png

The CO2-CO2 continuum file combines:

• the COA CIA band at 0-250cm-1 (Gruszka and Borysow, 1997), extrapolated down to 100K.
• All CIA and dimer bands listed in Tran et al. 2024 (see Table), using the functional formula for the shape and band intensity (as a function of temperature). Temperature dependency is extended from 100 to 800K.

N2-N2

The N2-N2 continuum file combines all data (roto-translational, fundamental and first overtone bands) from Karman+2019: https://hitran.org/cia/ (N2-N2_2021.cia file).

N2-N2 CIA new database fev2025.png

O2-O2

The O2-O2 continuum file combines all data from Karman+2019: https://hitran.org/cia/ (O2-O2_2018b.cia and O2-O2_theory_temp_2018.cia files).

O2-O2 CIA new database fev2025.png

CH4-CH4

The CH4-CH4 continuum file combines all data from Karman+2019: https://hitran.org/cia/ (CH4-CH4_2011.cia file). Only a single CH4 CIA band has been characterized so far (see Borysow & Frommhold 1987).

CH4-CH4 CIA new database fev2025.png

H2O-H2O

The H2O-H2O continuum is taken and interpolated from the MT_CKD continuum v_4.0.1 (https://github.com/AER-RC/MT_CKD_H2O). The H2O-H2O MT_CKD continuum is frequently updated, but most of the time the changes are very minor.

Note that the H2O-H2O MT_CKD continuum includes CIA and dimer bands, but also the absorption from the far wing (anything that absorbs beyond +/- 25cm-1 of each H2O line) and the plinth (the absorption at +/- 25cm-1) of H2O monomers (broadened by H2O).

Note that give the assumption of the MT_CKD continuum (continuum above 25cm-1), it is required that a 25cm-1 cutoff is applied to the absorption by the H2O monomers, and that the plinth is removed.

H2O-H2O CIA new database fev2025.png

H2-H2

The H2-H2 continuum file combines the H2-H2 file previously used for temperate-to-hot gas giants (H2-H2_2011_extended.cia.txt extended to wavelengths > 10,000cm-1 and temperatures up to 10,000K ; work done by Lucas Teinturier using codes provided by Bruno Bézard) and the (low-temperature) H2-H2 file used for solar system giant planets (provided by Gwenael Milcareck). The first file is used for T>400K and the second file for T<=400K.

We took the "equilibrium" files which is the most accurate choice in general for most of our giant planet (H2-rich atmospheres) applications. Differences between "equilibrium" and "norm" appear at temperatures << 100K.

H2-H2 CIA new database fev2025.png

CO2-H2

The CO2-H2 continuum file combines all data from Turbet+20, Mondelain+21 and Fakhardji+21.

CO2-H2 CIA new database fev2025.png

CO2-CH4

The CO2-H2 continuum file is built from Turbet+20.

CO2-CH4 new database fev2025.png

CO2-O2

The CO2-O2 continuum file combines all data from Karman+2019: https://hitran.org/cia/ (O2-CO2_2011.cia file) and data from Baranov et al. 2004 (digitized from Fig. 7).

CO2-O2 new database fev2025.png

O2-N2

The O2-N2 continuum file combines all data from Karman+2019: https://hitran.org/cia/ (O2-N2_2021.cia and O2-N2_theory_temp_2018.cia).

O2-N2 new database fev2025.png

H2O-AIR (H2O-O2 / H2O-N2)

The H2O-AIR continuum is taken and interpolated from the MT_CKD continuum v_4.0.1 (https://github.com/AER-RC/MT_CKD_H2O)

Note that the H2O-AIR MT_CKD continuum includes CIA and dimer bands, but also the absorption from the far wing (anything that absorbs beyond +/- 25cm-1 of each H2O line) and the plinth (the absorption at +/- 25cm-1) of H2O monomers (broadened by "air").

Note that "AIR" here corresponds to the present-day Earth mixture of O2 and N2. In practice in the model, we will use the H2O-AIR continuum for both H2O-O2 and H2O-N2 continuum.

Note that give the assumption of the MT_CKD continuum (continuum above 25cm-1), it is required that a 25cm-1 cutoff is applied to the absorption by the H2O monomers, and that the plinth is removed.

In practice, we take the H2O-O2 continuum equal to the MT_CKD H2O-AIR continuum. The H2O-N2 continuum is taken equal to the H2O-AIR MT_CKD continuum + the CIA band of Baranov+2012/Hartmann+2017 near 2400cm-1.

H2O-AIR/H2O-O2 new database fev2025.png

H2O-N2 new database fev2025.png

H2O-CO2

The H2O-CO2 continuum file was recalculated following the procedure described in Tran, Turbet et al. 2018 (using HITRAN 2016 line list modified with CO2-broadening coefficient) and extended up to 20,000cm-1. The temperature dependency was calculated using Ma & Tipping 1992 results (only from 0-10000cm-1, because we have no data above).

We also added the H2O-CO2 CIA band from Fleurbaey et al. 2022 (but the temperature dependency is not known).

Note that we followed the MT_CKD framework (continuum above 25cm-1), so it is required that a 25cm-1 cutoff is applied to the absorption by the H2O monomers, and that the plinth is removed.

H2O-CO2 new database fev2025.png

CH4-N2

The CH4-N2 continuum file combines all data from Karman+2019: https://hitran.org/cia/ (N2-CH4_2011.cia file).

CH4-N2 new database fev2025.png

H2-N2

The H2-N2 continuum file combines all data from Karman+2019: https://hitran.org/cia/ (N2-H2_2011.cia).

H2-N2 new database fev2025.png

H2-He

The H2-He continuum file combines the H2-He file previously used for temperate-to-hot gas giants (H2-He_2011.cia file provided in HITRAN) and the (low-temperature) H2-He file used for solar system giant planets (provided by Gwenael Milcareck ; file name was H2-He_eq_0-15000cm-1_40-400K.cia) and that we extended up to 20,000cm-1. The first file is used for T>400K and the second file for T<=400K.

We took the "equilibrium" file which is the most accurate choice in general for most of our giant planet (H2-rich atmospheres) applications. Differences between "equilibrium" and "norm" appear at temperatures << 100K.

H2-He new database fev2025.png

H2-CH4

The H2-CH4 continuum file combines all data from Karman+2019: https://hitran.org/cia/ (H2-CH4_eq_2011.cia). We took the "equilibrium" file which is the most accurate choice in general for most of our giant planet (H2-rich atmospheres) applications. Differences between "equilibrium" and "norm" appear at temperatures << 100K.

H2-CH4 new database fev2025.png