J/A+A/664/A82 3D GCMs mini-chemical scheme with net reactions (Tsai+, 2022)
A mini-chemical scheme with net Reactions for 3D general circulation models..
I. Thermochemical kinetics.
Tsai S.-M., Lee E.K.H., Pierrehumbert R.
<Astron. Astrophys. 664, A82 (2022)>
=2022A&A...664A..82T 2022A&A...664A..82T (SIMBAD/NED BibCode)
ADC_Keywords: Models, atmosphere
Keywords: planets and satellites: atmospheres -
planets and satellites: composition - methods: numerical
Abstract:
Growing evidence has indicated that the global composition
distribution plays an indisputable role in interpreting observational
data. Three-dimensional general circulation models (GCMs) with a
reliable treatment of chemistry and clouds are particularly crucial in
preparing for upcoming observations. In attempts to achieve 3D
chemistry-climate modeling, the challenge mainly lies in the expensive
computing power required for treating a large number of chemical
species and reactions.
Motivated by the need for a robust and computationally efficient
chemical scheme, we devise a mini-chemical network with a minimal
number of species and reactions for H2-dominated atmospheres.
We apply a novel technique to simplify the chemical network from a
full kinetics model, VULCAN, by replacing a large number of
intermediate reactions with net reactions. The number of chemical
species is cut down from 67 to 12, with the major species of thermal
and observational importance retained, including H2O, CH4, CO,
CO2, C2H2, NH3, and HCN. The size of the total reactions is
also greatly reduced, from ∼800 to 20. We validated the mini-chemical
scheme by verifying the temporal evolution and benchmarking the
predicted compositions in four exoplanet atmospheres (GJ 1214b,
GJ 436b, HD 189733b, and HD 209458b) against the full kinetics of
VULCAN.
The mini-network reproduces the chemical timescales and composition
distributions of the full kinetics well within an order of magnitude
for the major species in the pressure range of 1bar-0.1mbar across
various metallicities and carbon-to-oxygen (C/O) ratios.
We have developed and validated a mini-chemical scheme using net
reactions to significantly simplify a large chemical network. The
small scale of the mini-chemical scheme permits simple use and fast
computation, which is optimal for implementation in a 3D GCM or a
retrieval framework. We focus on the thermochemical kinetics of net
reactions in this paper and address photochemistry in a follow-up
paper.
Description:
We provide the numerical rates of the six net reactions employed in
the mini-chemical scheme. The rate constants are tabulated for
temperatures and pressure in the range of 300-3000K and
103-10-6bar, for a grid of metallicities (0.1xsolar, solar,
10xsolar, 100xsolar, 500xsolar) and C/O ratios (C/O=0.25, solar,
C/O=1, C/O=2).
File Summary: Six tables of the same metallicity and C/O ratio are
grouped into 20 folders, named after _<C/O>. For example,
the folder "10Xsolar_CtoO025" contains the net reaction rates for 10
times solar metallicity and C/O=0.25. Each file in the folder
provides the rates of the corresponding net reactions. The first row
describes the net reaction and the second row shows the names of the
four columns: temperature (K), pressure (bar) , rate constant
(cm3/s), and the rate-limiting step used to compute the rate.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 131 120 List of files
01Xsolar/* . 6 Individual files for metallicity 0.1 x solar
01XsolarCtoO025/* . 6 Individual files for metallicity 0.1 x solar
01XsolarCtoO1/* . 6 Individual files for metallicity 0.1 x solar
01XsolarCtoO2/* . 6 Individual files for metallicity 0.1 x solar
solar/* . 6 Individual files for metallicity solar
solarCtoO025/* . 6 Individual files for metallicity solar
solarCtoO1/* . 6 Individual files for metallicity solar
solarCtoO2/* . 6 Individual files for metallicity solar
10Xsolar/* . 6 Individual files for metallicity 10 x solar
10XsolarCtoO025/* . 6 Individual files for metallicity 10 x solar
10XsolarCtoO1/* . 6 Individual files for metallicity 10 x solar
10XsolarCtoO2/* . 6 Individual files for metallicity 10 x solar
100Xsolar/* . 6 Individual files for metallicity 100 x solar
100XsolarCtoO025/* . 6 Individual files for metallicity 100 x solar
100XsolarCtoO1/* . 6 Individual files for metallicity 100 x solar
100XsolarCtoO2/* . 6 Individual files for metallicity 100 x solar
500Xsolar/* . 6 Individual files for metallicity 500 x solar
500XsolarCtoO025/* . 6 Individual files for metallicity 500 x solar
500XsolarCtoO1/* . 6 Individual files for metallicity 500 x solar
500XsolarCtoO2/* . 6 Individual files for metallicity 500 x solar
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 51 A51 --- FileName Name of the file
53-131 A79 --- Title Title of the file
--------------------------------------------------------------------------------
Byte-by-byte Description of file (#): [015s]*/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 F6.1 K T Temperature
9- 18 E10.4 bar Pbar Pressure
20- 30 E11.4 cm3/s RateCst Rate constant
34- 53 A20 --- Reaction rate-limiting step used to compute the rate
--------------------------------------------------------------------------------
Acknowledgements:
Shang-Min Tsai, shang-min.tsai(at)physics.ox.ac.uk
(End) Patricia Vannier [CDS] 12-Apr-2022