Rosenbrock Approach to the Treatment of Aqueous Chemistry in CMAQ
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Transcript of Rosenbrock Approach to the Treatment of Aqueous Chemistry in CMAQ
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Sciences Modeling and Analysis Division |Research Triangle Park, NC
April 19, 2023
Annmarie G. Carlton, Gerald Gipson, Shawn Roselle, Rohit Mathur
Rosenbrock Approach to the Treatment of Aqueous Chemistry in CMAQ
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
2
BACKGROUND
•Clouds cover ~60% of the Earth’s surface–Associated convective mixing and aqueous phase processes provide a mechanism for venting atmospheric constituents from the polluted boundary layer to the free troposphere, with substantial implications for long-range pollution transport and climate
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
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INTRODUCTIONEvolving knowledge indicates atmospheric aqueous phase chemistry is more complex than typical model mechanisms Current aqueous mechanism designed to predict sulfate
Current CMAQ aqueous chemistry module does not easily lend itself to expansion
Forward Euler solver for oxidation and bisection method for pH
(note linear convergence for bisection method)Stiffness induced by timescales of different orders of
magnitude (e.g., ●OH reactions)
ROS3 solver is a good candidate for solving atmospheric aqueous chemistry (Sandu et al., 1997; Djouad et al., 2002)
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
4
Multipollutant version of CMAQ
Simulation with update
Max=24.3 µg/m3
original simulation
Max=283.4 µg/m3
Unrealistic sulfate production:
-problem traced to aqueous chemistry solver technique.
-Incorporated the fix into CMAQv4.7.1
Figures courtesy of P. Dolwick
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
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CMAQ Aqueous Chemistry Map (aqchem.F)
Molar conc. = initial amt. – amt. deposited (mol L-1)
bisection for pH, initial guesses between 0.01 – 10
liquid conc. (mol L-1) SO4, HSO4, SO3, HSO3, CO3, HCO3, OH, NH4, HCO2, NO3, ClStart iteration and bisection (3000 iterations)Calc. final gas phase partial pressure of SO2, NH3, HNO3, HCOOH, CO2liquid conc. (mol L-1) SO4, HSO4, SO3, HSO3, CO3, HCO3, OH, NH4, HCO2, NO3, ClCheck for convergence
Compute ionic strength and activity coefficient (Davies Eqn.)
Calculate liquid concentrations and final gas phase concs. of oxdidants
Kinetic calcs
Cal. Min time step – check for large time step SIV oxidized < 0.05 of SIV oxidized since time 0, double DT
Don’t let DT > TAUCLD
Compute wet depositions and phase concentrations for each species
TIME = TAUCLD (OR 100 iterations)
Check for convergence
100 max. iterations
pH
partitioning
oxidation
deposition
partitioning
pH
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
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More Processes Solved Simultaneously with ROS3
1
1 1
)(i
j
i
jjijjijni khJkyhfk
)(')())(,()()( 000000 thytytythftyhty
Rosenbrock Method
s
iiinn kbyy
11Where: J is the Jacobian
Forward Euler Method
ijijib ,, are constants
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
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Enhance Calculation of Aqueous Chemistry in CMAQ
1. Comparison of ROS3 solver with a GEAR solver for atmospheric aqueous chemistry
tested in box model used chemical mechanism described in Barth
et al., 20032. Implemented ROS3 solver in CCTM with same aqueous chemical mechanism currently employed to understand solver-specific effects3. Testing:
- partitioning assumptions- expansion of the chemical mechanism
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
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1.) Comparison with Gear Solver in Box Model Test
ROS3
GEAR
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
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2.) Implementing ROS3 for CMAQ aqueous mechanism
•Gas-to-droplet partitioningCurrent assumption, instantaneous thermodynamic equilibrium according to Henry’s Law
•Oxidation Chemistry5 sulfur “family” reactions: S(IV) S(VI) via O3, H2O2, O2, MHP, PAA
2 organic reactions: GLY, MGLY + ●OH
•Wet Depostion
)()( aqAgA ii
AAi pHaqA )(
Current CMAQ Aqueous Processes
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
10
2.) Implementing ROS3 for CMAQ aqueous mechanism
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
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Accumulation mode SO4 comparisons
Forward Euler Method
ROS3 Method
surface layer < ~ 34 metersμg m-3
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
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Differences in accumulation mode SO4
aloft layer typical of cloud base
Forward Euler Method SO4 – ROS3 Method SO4
surface layer < ~ 34 meters
μg m-3
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
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3.) Enhancing CMAQ Aqueous Processes: More Explicit Chemistry
13) GLY + OH(+O2) GLYAC + HO2
14) GLYAC + OH OXLAC + HO2 + H2O
15) GLYAC- + OH OXLAC- + HO2 + H2O
16) OXLAC + OH 2CO2 + 2H2O
17) OXLAC- + OH CO2 + CO2 - + 2H2O
18) OXLAC2- + OH CO2+CO2 - + OH-
19) GLYAC ↔ H+ + GLYAC-
20) OXLAC ↔ H+ + OXLAC
21) OXLAC- ↔ H+ + OXLAC2-
22) GLYAC + H2O2 HCO2H + CO2 + H2O
23) HCO2H + OH CO2 + HO2 + H2O
24) HCO2- + OH CO2
- + H2O
25) HCO2H ↔ H+ + HCO2-
1) H2O2 + hv 2OH
2) OH+ H2O2 HO2 + H2O
3) HO2 + H2O2 OH + H2O + O2
4) HO2 + HO2 H2O2 + O2
5) OH+ HO2 H2O + O2
6) OH + O2 - OH- + O2
7) HCO3- + OH CO3- +
H2O
8) CO3- + O2
- CO32- + O2
9) CO3- + HCO2
- HCO3- +
CO2-
10) CO3- + H2O2 HCO3
- + HO2
11) CO2 (+H2O) ↔ H+ + HCO3-
12) HCO3- ↔ H+ + CO3
2-
Reactions are taken from Lim et al. (2005); Carlton et al., (2008); Tan et al., (2009) and Refs. Therein.
GLY + OH ORGC
HOx chemistry Glyoxal oxidation chemistry
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
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3.) Enhancing CMAQ Aqueous Processes: Partitioning
HRT
AkGLkSQ
dt
dA imtimtAA
i
HRT
Ak imt
volatilization
aqueous production
sink reactions
accommodation
interfacial processes by Schwartz (1986) 12
)3
4
3(
d
g
dmt
R
D
Rk 2/1)
8(MW
RT
Theoretical maximum
Current CMAQ approachAi(g) Ai (aq)
Ai(aq) Ai (g)
imtGLk
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
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Findings and Implications
•In box model testing ROS3 represents a plausible technique to solve atmospheric aqueous phase chemistry–potentially more robust method than current method
•Successful implementation of the ROS3 solver to solve aqueous system in CMAQ–Beta version run time is slower but still optimizing
Office of Research and Development | National Exposure Research LaboratoryAtmospheric Modeling and Analysis Division | Research Triangle Park, NC
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Future Directions•Put wet deposition back in•Aqchem with ROS3 as an option in FY11 CMAQ release–Test this solver for different seasons, e.g., winter
•Incorporate more explicit chemistry into CMAQ–Find balance between more explicit chemistry and computational efficiency
•Compare with ground-base and aloft observational data –Speciated rain, cloud, deposition measurements