SuperFast
SuperFast gas-phase atmospheric chemistry mechanism from GasChem.jl. 12 active species + 3 quasi-constant reservoirs (O2/CH4/H2O; constant=true per ESS gt-ertm), 27 reactions covering tropospheric ozone chemistry. Regenerated from the upstream MTK ReactionSystem via mtk2esm (ESS gt-dod2). Fractional stoichiometries preserved directly (ESS gt-1e96); rate-law wrappers (arrhenius, third-body falloff, JPL 15-10 OH+CO, H2O-dependent HO2+HO2) inlined as Expression trees.
Description
SuperFast gas-phase atmospheric chemistry mechanism from GasChem.jl. 12 active species + 3 quasi-constant reservoirs (O2/CH4/H2O; constant=true per ESS gt-ertm), 27 reactions covering tropospheric ozone chemistry. Regenerated from the upstream MTK ReactionSystem via mtk2esm (ESS gt-dod2). Fractional stoichiometries preserved directly (ESS gt-1e96); rate-law wrappers (arrhenius, third-body falloff, JPL 15-10 OH+CO, H2O-dependent HO2+HO2) inlined as Expression trees.
Reference
Brown-Steiner, B., Selin, N. E., Prinn, R. G., Tilmes, S., Emmons, L., Lamarque, J.-F., and Cameron-Smith, P.: Evaluating simplified chemical mechanisms within present-day simulations of the Community Earth System Model version 1.2 with CAM4 (CESM1.2 CAM-chem): MOZART-4 vs. Reduced Hydrocarbon vs. Super-Fast chemistry, Geoscientific Model Development, 11, 4155-4174, 2018.
_Source: GasChem.jl src/SuperFast.jl @ 8c12c048482b515fb8eb2110bf8ab4b4f4e71309. Regenerated via mtk2esm (ESS gt-dod2) during mdl-xa2; previously hand-written in mdl-dkw. Fractional stoichiometries (CH3O2+CH3O2 -> 2.0 CH2O + 0.8 HO2; ISOP+O3 -> 0.87 CH2O + 1.86 CH3O2 + 0.06 HO2 + 0.05 CO; H2O+NO2 -> 0.5 HNO3; ISOP+OH -> ISOP + 0.5 OH) are preserved directly (gt-1e96). O2, CH4, H2O travel as isconstantspecies parameters in the upstream MTK model and are serialized as ESM species with constant=true (gt-ertm). Rate-law wrappers (arrh, arr_3rd, rate_2HO2, rate_OH_CO, rate_toppb) are inlined as closed-form expressions in T, P, and the H2O reservoir species, rather than preserved as composed sub-systems — the composed form yielded unresolved <subsys>.k(t) references in the reaction rates.
HO2 + HO2 (R4) water-vapour enhancement: upstream SuperFast.jl writes the factor as 1 + 1.4e-21H2OH2O_ppb_molec_cm3exp(2200/T), multiplying by the water mixing ratio twice, and the inlined rate here carried the same H2O^2. The JPL form is 1 + 1.4e-21[H2O]exp(2200/T) with [H2O] the water number density (molec/cm^3), which is what R4 now uses (the 8.428e-7P/(8314000*T) prefactor converts H2O from ppb to molec/cm^3 once). At the defaults the factor drops from ~3.2e7 to 2.74; with the squared term HO2 + HO2 was the dominant HO2 sink by seven orders of magnitude and held HO2/OH near 0.003, against ~7 now. The test expected values were regenerated after the fix: the Python and Rust bindings agree on every assertion to <=1e-8 relative, except the near-zero ISOP values (<=6e-4, inside their 5e-3 tolerance). See also superfast_ratelaws.esm, rate_2HO2._
- DOI: 10.5194/gmd-11-4155-2018
- URL: https://gmd.copernicus.org/articles/11/4155/2018/
Parameters
| Name | Units | Default | Description |
|---|---|---|---|
jNO2 | 1/s | 0.0149 | Photolysis NO2 |
T | K | 280 | Temperature |
P | Pa | 101325 | Pressure |
jH2COb | 1/s | 0.00014 | Photolysis CH2O (molecular channel) |
jH2COa | 1/s | 0.00014 | Photolysis CH2O (radical channel) |
jH2O2 | 1/s | 1.0097e-05 | Photolysis H2O2 |
jCH3OOH | 1/s | 8.9573e-06 | Photolysis CH3OOH |
jO32OH | 1/s | 0.000227 | Photolysis O3 + hv -> 2 OH (simplified, incl O1D+H2O) |
Species
| Species | Units | Default | Constant | Description |
|---|---|---|---|---|
O2 | ppb | 209500000 | yes | Molecular oxygen (constant reservoir) |
NO | ppb | 0.0004 | Nitric oxide | |
CO | ppb | 100 | Carbon monoxide | |
ISOP | ppb | 1e-11 | Isoprene | |
HNO3 | ppb | 4e-06 | Nitric acid | |
NO2 | ppb | 0.0004 | Nitrogen dioxide | |
HO2 | ppb | 4e-06 | Hydroperoxyl radical | |
CH3OOH | ppb | 4e-06 | Methyl hydroperoxide | |
OH | ppb | 4e-06 | Hydroxyl radical | |
O3 | ppb | 40 | Ozone | |
CH4 | ppb | 1700 | yes | Methane (constant reservoir) |
H2O | ppb | 18390000 | yes | Water vapor (constant reservoir) |
H2O2 | ppb | 4e-06 | Hydrogen peroxide | |
CH3O2 | ppb | 4e-06 | Methyl peroxy radical | |
CH2O | ppb | 4e-06 | Formaldehyde |
Expression Templates
arrh_per_molecule
Parameters: A, B
Reactions
| ID | Substrates | Products | Rate | |
|---|---|---|---|---|
R1 | O3 + OH | → | HO2 + O2 | $$\mathrm{arrh_per_molecule}\left(A=1023.4, B=-940\right)$$ |
R2 | O3 + HO2 | → | OH + 2 O2 | $$\mathrm{arrh_per_molecule}\left(A=6.02, B=-490\right)$$ |
R3 | HO2 + OH | → | H2O + O2 | $$\mathrm{arrh_per_molecule}\left(A=28896, B=250\right)$$ |
R4 | 2 HO2 | → | H2O2 + O2 | $$\left(\frac{180.6 \cdot P \cdot e^{\frac{460}{T}}}{8314000 \cdot T} + \frac{761048.4 \cdot P^{2} \cdot e^{\frac{920}{T}}}{69122596000000 \cdot T^{2}}\right) \cdot \left(1 + \frac{8.428 \times 10^{-7} \cdot P \cdot H2O \cdot e^{\frac{2200}{T}}}{8314000 \cdot T}\right)$$ |
R5 | H2O2 + OH | → | H2O + HO2 | $$\frac{1083.6 \cdot e^{0} \cdot P}{8314000 \cdot T}$$ |
R6 | NO + O3 | → | NO2 + O2 | $$\mathrm{arrh_per_molecule}\left(A=1806, B=-1500\right)$$ |
R7 | NO + HO2 | → | NO2 + OH | $$\mathrm{arrh_per_molecule}\left(A=1986.6000000000001, B=270\right)$$ |
R8 | NO2 + OH | → | HNO3 | $$\frac{652327200 \cdot e^{0} \cdot P^{2} \cdot 0.6^{\frac{1}{1 + \log_{10}\left(\frac{5423448340800000 \cdot P \cdot \frac{300}{T}^{3}}{1165130478176000000 \cdot T}\right)^{2}}} \cdot \frac{300}{T}^{3}}{69122596000000 \cdot T^{2} \cdot \left(1 + \frac{5423448340800000 \cdot P \cdot \frac{300}{T}^{3}}{1165130478176000000 \cdot T}\right)}$$ |
R9 | CH4 + OH | → | H2O + CH3O2 | $$\mathrm{arrh_per_molecule}\left(A=1474.8999999999999, B=-1775\right)$$ |
R10 | CO + OH | → | HO2 | $$\frac{641455080 \cdot P^{2} \cdot 0.6^{\frac{1}{1 + \log_{10}\left(\frac{5333057535120000 \cdot P \cdot \frac{300}{T}^{1.3}}{45772983071199992 \cdot T^{2}}\right)^{2}}} \cdot e^{0}}{69122596000000 \cdot T^{3} \cdot \left(1 + \frac{5333057535120000 \cdot P \cdot \frac{300}{T}^{1.3}}{45772983071199992 \cdot T^{2}}\right)} + \frac{90.3 \cdot P \cdot e^{0} \cdot 0.6^{\frac{1}{1 + \log_{10}\left(\frac{4.5195402839999995 \times 10^{32} \cdot P \cdot \frac{300}{T}^{6.1}}{8.738478586320001 \times 10^{37} \cdot T}\right)^{2}}}}{8314000 \cdot T \cdot \left(1 + \frac{4.5195402839999995 \times 10^{32} \cdot P \cdot \frac{300}{T}^{6.1}}{8.738478586320001 \times 10^{37} \cdot T}\right)}$$ |
R11 | OH + CH2O | → | CO + H2O + HO2 | $$\mathrm{arrh_per_molecule}\left(A=3311.0000000000005, B=125\right)$$ |
R12 | HO2 + CH3O2 | → | CH3OOH + O2 | $$\mathrm{arrh_per_molecule}\left(A=246.82000000000002, B=750\right)$$ |
R13 | CH3OOH + OH | → | H2O + CH3O2 | $$\mathrm{arrh_per_molecule}\left(A=1601.32, B=200\right)$$ |
R14 | CH3OOH + OH | → | H2O + OH + CH2O | $$\mathrm{arrh_per_molecule}\left(A=686.28, B=200\right)$$ |
R15 | NO + CH3O2 | → | NO2 + HO2 + CH2O | $$\mathrm{arrh_per_molecule}\left(A=1685.6000000000001, B=300\right)$$ |
R16 | 2 CH3O2 | → | 0.8 HO2 + 2 CH2O | $$\mathrm{arrh_per_molecule}\left(A=57.19, B=390\right)$$ |
R17 | H2O + NO2 | → | 0.5 HNO3 | $$\frac{2.408 \times 10^{-9} \cdot P}{8314000 \cdot T}$$ |
R18 | ISOP + OH | → | 2 CH3O2 | $$\mathrm{arrh_per_molecule}\left(A=16254, B=390\right)$$ |
R19 | ISOP + OH | → | ISOP | $$\mathrm{arrh_per_molecule}\left(A=16254, B=390\right)$$ |
R20 | ISOP + OH | → | ISOP + 0.5 OH | $$\mathrm{arrh_per_molecule}\left(A=16254, B=390\right)$$ |
R21 | O3 + ISOP | → | 0.05 CO + 0.06 HO2 + 0.87 CH2O + 1.86 CH3O2 | $$\mathrm{arrh_per_molecule}\left(A=3.3651799999999996, B=-1814\right)$$ |
R22 | O3 | → | 2 OH | $$jO32OH$$ |
R23 | H2O2 | → | 2 OH | $$jH2O2$$ |
R24 | NO2 | → | NO + O3 | $$jNO2$$ |
R25 | CH2O | → | CO + 2 HO2 | $$jH2COa$$ |
R26 | CH2O | → | CO | $$jH2COb$$ |
R27 | CH3OOH | → | HO2 + OH + CH2O | $$jCH3OOH$$ |
Analyses
jNO2_photolysis_sweep
NO2-photolysis sensitivity. Sweeps the NO2 photolysis rate jNO2 from dark (0 s^-1) to bright-noon (~0.02 s^-1) at default T, P, and initial composition. Higher jNO2 drives faster NO/NO2/O3 photostationary cycling and feeds OH via the secondary O3+hv channel; the lower bound (jNO2=0) is the overnight limit where the photochemical OH source shuts down. Useful for inspecting the dark-to-noon transition without running a full diurnal cycle.
Time span: 0 → 1
Swept over: jNO2
temperature_sweep
Tropospheric-temperature sensitivity. Sweeps T from 240 K (cold upper troposphere) to 320 K (warm boundary layer) at default P=101325 Pa. The bimolecular Arrhenius rates (NO+O3, OH+CO, OH+CH4, ISOP+OH, ISOP+O3) and the termolecular falloff rates (NO2+OH+M, OH+CO+M) all carry strong T dependence — this sweep makes the net effect on tropospheric ozone visible in a single curve. Useful for sanity-checking the T-dependence of the inlined Arrhenius/falloff rate-law expressions.
Time span: 0 → 1
Swept over: T
pressure_altitude_sweep
Vertical (pressure) sensitivity. Sweeps P from 30000 Pa (~9 km, upper troposphere) to 101325 Pa (surface) at fixed T=280 K. All inlined rate-law expressions divide by 8.314e6 * T (the per-molecule conversion factor) and scale with P^1 (bimolecular) or P^2 (third-body falloff for NO2+OH+M, OH+CO+M). This sweep illustrates the pressure dependence of the third-body channels relative to the bimolecular channels, and how chemical regime shifts with altitude.
Time span: 0 → 1
Swept over: P
default_run_24h
Illustrative 24-hour integration under default initial conditions and constant-day photolysis rates. Plots O3 vs. time. Initial conditions are the per-species reservoir defaults declared on the reaction system (O3=40 ppb, NO=NO2=0.4 ppt, etc.); photolysis-rate parameters (jNO2, jH2O2, …) hold at their declared bright-noon values for the full integration window.
Time span: 0 → 86400
Raw .esm
Raw .esm JSON (this component)
{
"tests": [
{
"time_span": {
"start": 0,
"end": 360
},
"id": "base_defaults_multi_species_multi_time",
"assertions": [
{
"expected": 39.39320259139222,
"time": 60,
"variable": "O3"
},
{
"expected": 38.21102425553218,
"time": 180,
"variable": "O3"
},
{
"expected": 36.515318706423145,
"time": 360,
"variable": "O3"
},
{
"expected": 0.014973954645431609,
"time": 60,
"variable": "OH"
},
{
"expected": 0.014220800015359584,
"time": 180,
"variable": "OH"
},
{
"expected": 0.01300187434251459,
"time": 360,
"variable": "OH",
"tolerance": {
"rel": 0.0005
}
},
{
"expected": 0.09898356849572909,
"time": 60,
"variable": "HO2"
},
{
"expected": 0.09301492196584987,
"time": 180,
"variable": "HO2"
},
{
"expected": 0.09035848137289122,
"time": 360,
"variable": "HO2"
},
{
"expected": 0.0005131039816090788,
"time": 60,
"variable": "NO2"
},
{
"expected": 0.00034910864362813033,
"time": 180,
"variable": "NO2"
},
{
"expected": 0.00018819921981223239,
"time": 360,
"variable": "NO2",
"tolerance": {
"rel": 0.0005
}
}
],
"description": "Run from the upstream GasChem.jl defaults. Integrates 0..360 s and samples 4 active species at 4 times each. The expected values are this document's own (Python and Rust bindings agree to <=1e-8 relative); they no longer match upstream SuperFast, whose HO2 + HO2 water term squares H2O (see the reaction system notes).\n\nTolerance rationale (test-level rel=1e-4): default band — absorbs integrator differences between the bindings (the expected values are no longer compared against the upstream Rosenbrock23 run); set per mdl-1k5 after the Python runner exposed CSE-reorder noise on radical pathways. Per-assertion overrides: OH @360s and NO2 @360s use rel=5e-4 (5× looser) — stiff radicals near steady state at end-of-window, where step-size adaptation between integrators diverges and CSE-reorder noise amplifies relative-comparison drift on small-magnitude values.",
"tolerance": {
"rel": 0.0001
}
},
{
"time_span": {
"start": 0,
"end": 360
},
"id": "base_defaults_radical_pool",
"assertions": [
{
"expected": 0.19097455276829742,
"time": 360,
"variable": "CH3O2",
"tolerance": {
"rel": 0.0005
}
},
{
"expected": 0.5345601149850574,
"time": 360,
"variable": "CH3OOH",
"tolerance": {
"rel": 0.0005
}
},
{
"expected": 0.1751750058974256,
"time": 360,
"variable": "CH2O",
"tolerance": {
"rel": 0.001
}
},
{
"expected": 0.6004902099062742,
"time": 360,
"variable": "H2O2"
},
{
"expected": 0.000576442168892365,
"time": 360,
"variable": "HNO3"
},
{
"expected": 96.87255926148784,
"time": 360,
"variable": "CO"
},
{
"expected": 4.591947726881975e-18,
"time": 360,
"variable": "ISOP",
"tolerance": {
"rel": 0.005
}
}
],
"description": "Radical pool values (CH3O2, CH3OOH, CH2O, H2O2, HNO3, CO, ISOP) at t=360 s under default initial conditions. Guards against structural drift in the CH3O2 and HxOy pathways.\n\nTolerance rationale (test-level rel=1e-4): default band per mdl-1k5 (Rosenbrock23 ↔ lambdify cse=True drift). Per-assertion overrides reflect species-specific stiffness: CH3O2 / CH3OOH @360s use rel=5e-4 (5× looser, near-steady-state radicals); CH2O uses rel=1e-3 (10× looser — fractional-stoichiometry products from CH3O2+CH3O2 R16 [stoich 2.0] and ISOP+O3 R21 [stoich 0.87] compound truncation, and the multi-channel CH2O budget magnifies CSE-reorder drift); ISOP uses rel=5e-3 (50× looser — ISOP @360s has decayed to ~4.6e-18 ppb, so relative comparison amplifies LSODA truncation noise on near-numerical-zero values).",
"tolerance": {
"rel": 0.0001
}
},
{
"tolerance": {
"rel": 0.0001
},
"time_span": {
"start": 0,
"end": 3600
},
"id": "high_nox_photostationary_1h",
"assertions": [
{
"expected": 54.25591030539415,
"time": 600,
"variable": "O3"
},
{
"expected": 28.76735693348619,
"time": 3600,
"variable": "O3",
"tolerance": {
"rel": 0.0005
}
},
{
"expected": 2.050416934615542,
"time": 600,
"variable": "NO"
},
{
"expected": 3.697440554409655e-05,
"time": 3600,
"variable": "NO",
"tolerance": {
"rel": 0.002
}
},
{
"expected": 3.5207702158826177,
"time": 600,
"variable": "NO2"
},
{
"expected": 0.00017675559018342056,
"time": 3600,
"variable": "NO2",
"tolerance": {
"rel": 0.002
}
},
{
"expected": 14.424478363703374,
"time": 600,
"variable": "HNO3"
},
{
"expected": 19.994537057035767,
"time": 3600,
"variable": "HNO3"
}
],
"description": "High-NOx photochemical-smog-ish regime: initial NO=10, NO2=10, O3=60, ISOP=0.5 ppb. Integrated 0..3600 s. Checks photostationary state of the NO/NO2/O3 triad and build-up of HNO3 via NO2+OH. Failure here indicates the NO2 photolysis / NO+O3 / HO2+NO / NO2+OH+M loop has drifted.\n\nTolerance rationale (test-level rel=1e-4): default band per mdl-1k5. Per-assertion overrides at t=3600 s reflect the photostationary turnover: O3 uses rel=5e-4 (5× looser, near-steady-state); NO and NO2 use rel=2e-3 (20× looser) — both species swing 2 orders of magnitude as O3+NO drains NO and NO2+OH+M produces HNO3, and Rosenbrock23 ↔ LSODA step-size adaptation diverges sharply across the photostationary turnover.",
"initial_conditions": {
"NO": 10,
"O3": 60,
"ISOP": 0.5,
"NO2": 10
}
},
{
"parameter_overrides": {
"jNO2": 0,
"jH2COb": 0,
"jH2COa": 0,
"jH2O2": 0,
"jCH3OOH": 0,
"jO32OH": 0
},
"time_span": {
"start": 0,
"end": 1800
},
"id": "dark_all_photolysis_zero_30min",
"assertions": [
{
"expected": 39.99959974182895,
"time": 1800,
"variable": "O3"
},
{
"expected": 1.0314305852209193e-15,
"time": 1800,
"variable": "NO",
"tolerance": {
"rel": 0.001,
"abs": 1e-12
}
},
{
"expected": 0.0007972805261944212,
"time": 1800,
"variable": "NO2"
},
{
"expected": 7.148207937741515e-09,
"time": 1800,
"variable": "OH"
},
{
"expected": 3.5015467552483854e-06,
"time": 1800,
"variable": "HO2"
}
],
"description": "Overnight / dark chemistry: all photolysis rates (jO32OH, jH2O2, jNO2, jH2COa, jH2COb, jCH3OOH) forced to 0. Integrated 0..1800 s. Without photolysis, OH/HO2 should relax toward zero while O3 and NO2 decay slowly. This exercises the parameter-override path and guards against runaway radical production without a radical source.\n\nTolerance rationale (test-level rel=1e-4 / abs=1e-14): default rel band; abs=1e-14 floors per-species comparisons for the active radicals that decay to near-numerical-zero in the absence of photolytic radical sources. NO @1800s is the one per-assertion override, rel=1e-3 / abs=1e-12: NO ≈ 1e-15 ppb, so abs is the operative floor there, and without it a rel comparison alone diverges as NO → 0. OH (≈ 7.1e-9 ppb) and HO2 (≈ 3.5e-6 ppb) sit orders of magnitude above abs and take the default rel=1e-4; they carried looser overrides (OH rel=1e-3, HO2 rel=1e-2) from when the squared R4 water term held them near the abs floor, and since the R4 fix this test is a check on it.",
"tolerance": {
"rel": 0.0001,
"abs": 1e-14
}
},
{
"time_span": {
"start": 0,
"end": 1
},
"id": "initial_conditions_t0",
"assertions": [
{
"expected": 40,
"time": 0,
"variable": "O3"
},
{
"expected": 4e-06,
"time": 0,
"variable": "OH"
},
{
"expected": 4e-06,
"time": 0,
"variable": "HO2"
},
{
"expected": 0.0004,
"time": 0,
"variable": "NO"
},
{
"expected": 0.0004,
"time": 0,
"variable": "NO2"
},
{
"expected": 4e-06,
"time": 0,
"variable": "CH3O2"
},
{
"expected": 4e-06,
"time": 0,
"variable": "CH2O"
},
{
"expected": 100,
"time": 0,
"variable": "CO"
},
{
"expected": 4e-06,
"time": 0,
"variable": "CH3OOH"
},
{
"expected": 1e-11,
"time": 0,
"variable": "ISOP"
},
{
"expected": 4e-06,
"time": 0,
"variable": "H2O2"
},
{
"expected": 4e-06,
"time": 0,
"variable": "HNO3"
}
],
"description": "At t=0, the solver must return the declared defaults for every active species.\n\nTolerance rationale (test-level rel=1e-10 / abs=1e-14): initial-condition assertion at t=0 — solver must return declared species defaults exact-to-roundoff; rel=1e-10 / abs=1e-14 covers only parser → MTK/lambdify float conversion and the first solver step's identity-evaluation of initial state. Tighter than every other test in this file because no integration drift has accumulated.",
"tolerance": {
"rel": 1e-10,
"abs": 1e-14
}
},
{
"tolerance": {
"rel": 0.0001
},
"time_span": {
"start": 0,
"end": 1800
},
"id": "isoprene_chemistry_elevated",
"assertions": [
{
"expected": 32.53151311885282,
"time": 1800,
"variable": "O3"
},
{
"expected": 3.052111630339415e-11,
"time": 1800,
"variable": "ISOP",
"tolerance": {
"rel": 0.005
}
},
{
"expected": 0.21274207744793766,
"time": 1800,
"variable": "CH3O2",
"tolerance": {
"rel": 0.002
}
},
{
"expected": 1.6187708662241425,
"time": 1800,
"variable": "CH2O",
"tolerance": {
"rel": 0.002
}
},
{
"expected": 101.51034047146955,
"time": 1800,
"variable": "CO"
}
],
"description": "Elevated isoprene (ISOP=5 ppb, O3=50 ppb) for 1800 s. Exercises the fractional-stoichiometry products of ISOP+O3 (0.87 CH2O + 1.86 CH3O2 + 0.06 HO2 + 0.05 CO) and of the ISOP+OH channels (two of which carry fractional product stoich).\n\nTolerance rationale (test-level rel=1e-4): default band per mdl-1k5. Per-assertion overrides reflect species behaviour: ISOP @1800s uses rel=5e-3 (50× looser — ISOP has decayed to ~3.1e-11 ppb, near numerical zero); CH3O2 and CH2O @1800s use rel=2e-3 (20× looser — both are downstream products of fractional-stoichiometry channels that compound truncation, and CH3O2 in particular has Rosenbrock23↔LSODA step-size-adaptation drift in the active-radical regime).",
"initial_conditions": {
"O3": 50,
"ISOP": 5
}
}
],
"parameters": {
"jNO2": {
"units": "1/s",
"default": 0.0149,
"description": "Photolysis NO2"
},
"T": {
"units": "K",
"default": 280,
"description": "Temperature"
},
"P": {
"units": "Pa",
"default": 101325,
"description": "Pressure"
},
"jH2COb": {
"units": "1/s",
"default": 0.00014,
"description": "Photolysis CH2O (molecular channel)"
},
"jH2COa": {
"units": "1/s",
"default": 0.00014,
"description": "Photolysis CH2O (radical channel)"
},
"jH2O2": {
"units": "1/s",
"default": 1.0097e-05,
"description": "Photolysis H2O2"
},
"jCH3OOH": {
"units": "1/s",
"default": 8.9573e-06,
"description": "Photolysis CH3OOH"
},
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},
"reference": {
"doi": "10.5194/gmd-11-4155-2018",
"citation": "Brown-Steiner, B., Selin, N. E., Prinn, R. G., Tilmes, S., Emmons, L., Lamarque, J.-F., and Cameron-Smith, P.: Evaluating simplified chemical mechanisms within present-day simulations of the Community Earth System Model version 1.2 with CAM4 (CESM1.2 CAM-chem): MOZART-4 vs. Reduced Hydrocarbon vs. Super-Fast chemistry, Geoscientific Model Development, 11, 4155-4174, 2018.",
"notes": "Source: GasChem.jl src/SuperFast.jl @ 8c12c048482b515fb8eb2110bf8ab4b4f4e71309. Regenerated via mtk2esm (ESS gt-dod2) during mdl-xa2; previously hand-written in mdl-dkw. Fractional stoichiometries (CH3O2+CH3O2 -> 2.0 CH2O + 0.8 HO2; ISOP+O3 -> 0.87 CH2O + 1.86 CH3O2 + 0.06 HO2 + 0.05 CO; H2O+NO2 -> 0.5 HNO3; ISOP+OH -> ISOP + 0.5 OH) are preserved directly (gt-1e96). O2, CH4, H2O travel as isconstantspecies parameters in the upstream MTK model and are serialized as ESM species with constant=true (gt-ertm). Rate-law wrappers (arrh, arr_3rd, rate_2HO2, rate_OH_CO, rate_toppb) are inlined as closed-form expressions in T, P, and the H2O reservoir species, rather than preserved as composed sub-systems — the composed form yielded unresolved `<subsys>.k(t)` references in the reaction rates.\n\nHO2 + HO2 (R4) water-vapour enhancement: upstream SuperFast.jl writes the factor as 1 + 1.4e-21*H2O*H2O_ppb_molec_cm3*exp(2200/T), multiplying by the water mixing ratio twice, and the inlined rate here carried the same H2O^2. The JPL form is 1 + 1.4e-21*[H2O]*exp(2200/T) with [H2O] the water number density (molec/cm^3), which is what R4 now uses (the 8.428e-7*P/(8314000*T) prefactor converts H2O from ppb to molec/cm^3 once). At the defaults the factor drops from ~3.2e7 to 2.74; with the squared term HO2 + HO2 was the dominant HO2 sink by seven orders of magnitude and held HO2/OH near 0.003, against ~7 now. The test expected values were regenerated after the fix: the Python and Rust bindings agree on every assertion to <=1e-8 relative, except the near-zero ISOP values (<=6e-4, inside their 5e-3 tolerance). See also superfast_ratelaws.esm, rate_2HO2.",
"url": "https://gmd.copernicus.org/articles/11/4155/2018/"
},
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"default": 0.0004,
"description": "Nitric oxide"
},
"CO": {
"units": "ppb",
"default": 100,
"description": "Carbon monoxide"
},
"ISOP": {
"units": "ppb",
"default": 1e-11,
"description": "Isoprene"
},
"HNO3": {
"units": "ppb",
"default": 4e-06,
"description": "Nitric acid"
},
"NO2": {
"units": "ppb",
"default": 0.0004,
"description": "Nitrogen dioxide"
},
"HO2": {
"units": "ppb",
"default": 4e-06,
"description": "Hydroperoxyl radical"
},
"CH3OOH": {
"units": "ppb",
"default": 4e-06,
"description": "Methyl hydroperoxide"
},
"OH": {
"units": "ppb",
"default": 4e-06,
"description": "Hydroxyl radical"
},
"O3": {
"units": "ppb",
"default": 40,
"description": "Ozone"
},
"CH4": {
"constant": true,
"units": "ppb",
"default": 1700,
"description": "Methane (constant reservoir)"
},
"H2O": {
"constant": true,
"units": "ppb",
"default": 18390000,
"description": "Water vapor (constant reservoir)"
},
"H2O2": {
"units": "ppb",
"default": 4e-06,
"description": "Hydrogen peroxide"
},
"CH3O2": {
"units": "ppb",
"default": 4e-06,
"description": "Methyl peroxy radical"
},
"CH2O": {
"units": "ppb",
"default": 4e-06,
"description": "Formaldehyde"
}
},
"expression_templates": {
"arrh_per_molecule": {
"params": [
"A",
"B"
],
"body": {
"op": "/",
"args": [
{
"op": "*",
"args": [
"A",
"P",
{
"op": "exp",
"args": [
{
"op": "/",
"args": [
"B",
"T"
]
}
]
}
]
},
{
"op": "*",
"args": [
8314000,
"T"
]
}
]
}
}
},
"analyses": [
{
"id": "jNO2_photolysis_sweep",
"description": "NO2-photolysis sensitivity. Sweeps the NO2 photolysis rate jNO2 from dark (0 s^-1) to bright-noon (~0.02 s^-1) at default T, P, and initial composition. Higher jNO2 drives faster NO/NO2/O3 photostationary cycling and feeds OH via the secondary O3+hv channel; the lower bound (jNO2=0) is the overnight limit where the photochemical OH source shuts down. Useful for inspecting the dark-to-noon transition without running a full diurnal cycle.",
"time_span": {
"start": 0,
"end": 1
},
"parameter_sweep": {
"type": "cartesian",
"dimensions": [
{
"parameter": "jNO2",
"values": [
0.0,
0.001,
0.0025,
0.005,
0.0075,
0.01,
0.0149,
0.02
]
}
]
},
"plots": [
{
"id": "O3_vs_jNO2",
"type": "line",
"description": "Steady-state O3 vs NO2 photolysis rate jNO2.",
"x": {
"variable": "jNO2",
"label": "jNO2 (1/s)"
},
"y": {
"variable": "O3",
"label": "O3 (ppb)"
}
}
]
},
{
"id": "temperature_sweep",
"description": "Tropospheric-temperature sensitivity. Sweeps T from 240 K (cold upper troposphere) to 320 K (warm boundary layer) at default P=101325 Pa. The bimolecular Arrhenius rates (NO+O3, OH+CO, OH+CH4, ISOP+OH, ISOP+O3) and the termolecular falloff rates (NO2+OH+M, OH+CO+M) all carry strong T dependence — this sweep makes the net effect on tropospheric ozone visible in a single curve. Useful for sanity-checking the T-dependence of the inlined Arrhenius/falloff rate-law expressions.",
"time_span": {
"start": 0,
"end": 1
},
"parameter_sweep": {
"type": "cartesian",
"dimensions": [
{
"parameter": "T",
"values": [
240,
250,
260,
270,
280,
290,
300,
310,
320
]
}
]
},
"plots": [
{
"id": "O3_vs_T",
"type": "line",
"description": "Steady-state O3 vs temperature T.",
"x": {
"variable": "T",
"label": "Temperature (K)"
},
"y": {
"variable": "O3",
"label": "O3 (ppb)"
}
}
]
},
{
"id": "pressure_altitude_sweep",
"description": "Vertical (pressure) sensitivity. Sweeps P from 30000 Pa (~9 km, upper troposphere) to 101325 Pa (surface) at fixed T=280 K. All inlined rate-law expressions divide by 8.314e6 * T (the per-molecule conversion factor) and scale with P^1 (bimolecular) or P^2 (third-body falloff for NO2+OH+M, OH+CO+M). This sweep illustrates the pressure dependence of the third-body channels relative to the bimolecular channels, and how chemical regime shifts with altitude.",
"time_span": {
"start": 0,
"end": 1
},
"parameter_sweep": {
"type": "cartesian",
"dimensions": [
{
"parameter": "P",
"values": [
30000,
40000,
50000,
60000,
70000,
80000,
90000,
101325
]
}
]
},
"plots": [
{
"id": "O3_vs_P",
"type": "line",
"description": "Steady-state O3 vs ambient pressure P.",
"x": {
"variable": "P",
"label": "Pressure (Pa)"
},
"y": {
"variable": "O3",
"label": "O3 (ppb)"
}
}
]
},
{
"id": "default_run_24h",
"description": "Illustrative 24-hour integration under default initial conditions and constant-day photolysis rates. Plots O3 vs. time. Initial conditions are the per-species reservoir defaults declared on the reaction system (O3=40 ppb, NO=NO2=0.4 ppt, etc.); photolysis-rate parameters (jNO2, jH2O2, ...) hold at their declared bright-noon values for the full integration window.",
"time_span": {
"start": 0,
"end": 86400
},
"plots": [
{
"id": "O3_vs_time",
"type": "line",
"description": "Ozone concentration over 24 h.",
"x": {
"variable": "t",
"label": "time (s)"
},
"y": {
"variable": "O3",
"label": "O3 (ppb)"
}
}
]
}
]
}