Havala O. T. Pye, U.S. Environmental Protection Agency
Aero7 and aero7i build on the aero6 module. Scientific improvements in aero7/7i include:
- improved consistency in terms of secondary organic aerosol (SOA) between carbon bond and SAPRC-based mechanisms
- updated monoterpene SOA from photooxidation (OH and ozone)
- uptake of water onto hydrophillic organics
- reorganization of anthropogenic SOA species
- inorganic sulfate is consumed when IEPOX organosulfates are formed
Fewer species are required for aero7/7i, so more robust predictions require less computation time than aero6.
Figure 1: Organic aerosol treatment in CMAQv5.3-aero7. Note that the primary organic aerosol system is unchanged from CMAQv5.2 (Murphy et al. 2017) and abbreviated in this schematic. Species in red are new to aero7.
New species introduced in aero7 compared to aero6:
| Species | Phase | Description | Scientific Basis | Model Implementation | |
|---|---|---|---|---|---|
| 1 | AMT1J | particle | low volatility particulate matter from monoterpene photoxidation (OH and O3 reaction), C*=0.01 μg m‑3 | dark α‑pinene ozonolysis (Saha and Grieshop, 2016, ES&T) | Xu et al., 2018, ACP |
| 2 | AMT2J | particle | low volatility particulate matter from monoterpene photoxidation (OH and O3 reaction), C*=0.1 μg m‑3 | dark α‑pinene ozonolysis (Saha and Grieshop, 2016, ES&T) | Xu et al., 2018, ACP |
| 3 | AMT3J | particle | semivolatile particulate matter from monoterpene photoxidation (OH and O3 reaction), C*=1 μg m‑3 | dark α‑pinene ozonolysis (Saha and Grieshop, 2016, ES&T) | Xu et al., 2018, ACP |
| 4 | AMT4J | particle | semivolatile particulate matter from monoterpene photoxidation (OH and O3 reaction), C*=10 μg m‑3 | dark α‑pinene ozonolysis (Saha and Grieshop, 2016, ES&T) | Xu et al., 2018, ACP |
| 5 | AMT5J | particle | semivolatile particulate matter from monoterpene photoxidation (OH and O3 reaction), C*=100 μg m‑3 | dark α‑pinene ozonolysis (Saha and Grieshop, 2016, ES&T) | Xu et al., 2018, ACP |
| 6 | AMT6J | particle | semivolatile particulate matter from monoterpene photoxidation (OH and O3 reaction), C*=1000 μg m‑3 | dark α‑pinene ozonolysis (Saha and Grieshop, 2016, ES&T) | Xu et al., 2018, ACP |
| 7 | SVMT1 | gas | low volatility gas from monoterpene photoxidation (OH and O3 reaction), C*=0.01 μg m‑3 | dark α‑pinene ozonolysis (Saha and Grieshop, 2016, ES&T) | Xu et al., 2018, ACP |
| 8 | SVMT2 | gas | low volatility gas from monoterpene photoxidation (OH and O3 reaction), C*=0.1 μg m‑3 | dark α‑pinene ozonolysis (Saha and Grieshop, 2016, ES&T) | Xu et al., 2018, ACP |
| 9 | SVMT3 | gas | semivolatile gas from monoterpene photoxidation (OH and O3 reaction), C*=1 μg m‑3 | dark α‑pinene ozonolysis (Saha and Grieshop, 2016, ES&T) | Xu et al., 2018, ACP |
| 10 | SVMT4 | gas | semivolatile gas from monoterpene photoxidation (OH and O3 reaction), C*=10 μg m‑3 | dark α‑pinene ozonolysis (Saha and Grieshop, 2016, ES&T) | Xu et al., 2018, ACP |
| 11 | SVMT5 | gas | semivolatile gas from monoterpene photoxidation (OH and O3 reaction), C*=100 μg m‑3 | dark α‑pinene ozonolysis (Saha and Grieshop, 2016, ES&T) | Xu et al., 2018, ACP |
| 12 | SVMT6 | gas | semivolatile gas from monoterpene photoxidation (OH and O3 reaction), C*=1000 μg m‑3 | dark α‑pinene ozonolysis (Saha and Grieshop, 2016, ES&T) | Xu et al., 2018, ACP |
| 13 | AORGH2OJ | particle | water associated with organic species of particulate matter | hygroscopicity parameters (Petters and Kreidenweis, 2007, ACP) as a function of degree of oxygenation (Lambe et al., 2011, ACP) | Pye et al., 2017, ACP |
| 14 | AAVB1J | particle | low volatility organic particulate matter from oxidation of anthropogenic VOCs (benzene, toluene, xylene, PAHs, alkanes) | GEOS-Chem VBS parameterization (Pye et al., 2010, ACP) for aromatics and PAHs with long-chain alkanes following Pye and Pouliot (2012, ES&T) but with Presto et al. (2010, ES&T) VBS fits; all underlying experimental datasets are the same as in aero6 | Qin et al., in prep. |
| 15 | AAVB2J | particle | semivolatile organic particulate matter from oxidation of anthropogenic VOCs (benzene, toluene, xylene, PAHs, alkanes) | see AAVB1J | Qin et al., in prep. |
| 16 | AAVB3J | particle | semivolatile organic particulate matter from oxidation of anthropogenic VOCs (benzene, toluene, xylene, PAHs, alkanes) | see AAVB1J | Qin et al., in prep. |
| 17 | AAVB4J | particle | semivolatile organic particulate matter from oxidation of anthropogenic VOCs (benzene, toluene, xylene, PAHs, alkanes) | see AAVB1J | Qin et al., in prep. |
| 18 | SVAVB1 | gas | low volatility organic gas from oxidation of anthropogenic VOCs (benzene, toluene, xylene, PAHs, alkanes) | see AAVB1J | Qin et al., in prep. |
| 19 | SVAVB2 | gas | semivolatile organic gas from oxidation of anthropogenic VOCs (benzene, toluene, xylene, PAHs, alkanes) | see AAVB1J | Qin et al., in prep. |
| 20 | SVAVB3 | gas | semivolatile organic gas from oxidation of anthropogenic VOCs (benzene, toluene, xylene, PAHs, alkanes) | see AAVB1J | Qin et al., in prep. |
| 21 | SVAVB4 | gas | semivolatile organic gas from oxidation of anthropogenic VOCs (benzene, toluene, xylene, PAHs, alkanes) | see AAVB1J | Qin et al., in prep. |
| 22 | MTNO3 | gas | organic nitrates from monoterpene oxidation | gas-phase SAPRC yields (should not be counted as gas-phase organic nitrate for evaluation purposes in CB6r3 mechanisms) | Pye et al., 2015, ES&T |
| 23 | AMTNO3J | particle | semivolatile organic nitrates from monoterpene oxidation | Fry et al. (2009, ACP) for vapor pressure of monoterpene organic nitrates | Pye et al., 2015, ES&T |
| 24 | AMTHYDJ | particle | organic pseudo-hydrolysis accretion product from monoterpene organic nitrates (AMTNO3J) | Boyd et al. (2015, ACP) for hydrolysis timescale for tertiary nitrates, but applied to all MTNO3 following Pye et al. (2015, ES&T) | Pye et al., 2015, ES&T |
Species new to aero7i: species 1-21 of the above table. Other species in aero7i (including species 22-24 from above) previously existed in aero6i.
Species in aero6/6i that are deprecated in aero7/7i (these species should NOT appear in an aero7/7i namelist):
ATRP1J, ATRP2J, SV_TRP1, SV_TRP2, ABNZ1J, ABNZ2J, ABNZ3J, SV_BNZ1, SV_BNZ2, AXYL1J, AXYL2J, AXYL3J, SV_XYL1, SV_XYL2, ATOL1J, ATOL2J, ATOL3J, SV_TOL1, SV_TOL2, APAH1J, APAH2J, APAH3J, SV_PAH1, SV_PAH2, AALK1J, AALK2J, SV_ALK1, SV_ALK2
All gas-phase semivolatiles use species-specific wet and dry deposition surrogates.
Note that underscores are no longer used in species names in any aerosol or nonreactives namelist. For example, SV_ISO1 is now SVISO1 in the non-reactives namelist (NR*.nml).
The explicit monoterpene organic nitrate SOA from Pye et al. (2015) originally implemented in saprc07tic, has been ported to cb6r3-aero7 using the same assumptions as the saprc07tic-aero6i and aero7i implementation.
Aero7 and aero7i differ in terms of the degree of speciation of isoprene SOA. Specifically, isoprene epoxydiol (IEPOX) SOA (Pye et al. 2013, 2017) is represented using species AISO3J in aero7. In aero7i, AISO3J is approximately zero and IEPOX SOA is represented explicitly as organosulfates (AIEOSJ), 2-methyltetrols (AIETETJ), and dimers (AIDIMJ). In addition, aero7i includes explicit methylglyceric acid (AIMGAJ) and its analogous organosulfate (AIMOSJ), both of which are minor. Aero7i also includes a particle-phase isoprene dinitrate (Pye et al. 2015) that was not ported to aero7. Users may want to use aero7i if they require additional isoprene SOA speciation (for example, to evaluate with measurements).
Aero7 and aero7i require that α‑pinene (usually denoted APIN) is separate from all other monoterpenes (TERP) in the model. This is to avoid making SOA from α‑pinene + nitrate radical reactions as that pathway has been shown to produce negligible SOA. SAPRC07-based mechanisms, including the aero6 ones, already treat APIN as separate and mutally exclusive of TERP; saprc07tc aero6 emissions will work with aero7 without any adjustment. CB6r3 with aero6 continues to include APIN in TERP as it did in CMAQ v5.2.1.
If you have CB6r3-aero6 emissions and want to run CB6r3-aero7, options are:
- Reprocess your emissions to separate APIN from all other monoterpenes.
- Use the emission control file and assign 30% of emitted TERP to APIN and 70% of emitted TERP to TERP.
- If you are using inline biogenic emissions, do nothing and let CMAQ determine the correct biogenic speciation for your simulation.
Approach 1 is the most thorough and the only way to properly map anthropogenic monoterpene emissions (which are currently relatively minor in the inventory). It may not be necessary if your biogenic emissions are calculated inline within CMAQ. Approach 2 is an approxmimation based on assuming 30% of global monoterpene emissions are α‑pinene (Pye et al. 2010) and could be used if your biogenic emissions are preprocessed in input files. Approach 3 makes use of separate biogenic emission mapping profiles for CB6r3-aero6 and CB6r3-aero7 available within CMAQ (see biogenic emission update). Approach 3 is not an option if your biogenic emissions were pre-processed.
- Monoterpene SOA
- Reorganization of anthropogenic SOA species
- Uptake of water onto hydrophilic organic aerosol
Increased dry PM2.5 mass primarily in summer in vegetation-rich locations such as the southeast U.S. (Xu et al. 2018). Ambient PM2.5 is further increased due to water uptake with implications for metrics such as AOD that represent in situ (vs. dry) conditions.
CCTM/src/aero/aero7 (links to aero6)
hlconst.f
dry deposition files
Lambe, A. T., Onasch, T. B., Massoli, P., Croasdale, D. R., Wright, J. P., Ahern, A. T., Williams, L. R., Worsnop, D. R., Brune, W. H., and Davidovits, P.: Laboratory studies of the chemical composition and cloud condensation nuclei (CCN) activity of secondary organic aerosol (SOA) and oxidized primary organic aerosol (OPOA), Atmospheric Chemistry and Physics, 11, 8913-8928, https://doi.org/10.5194/acp-11-8913-2011, 2011.
Murphy, B. N., Woody, M. C., Jimenez, J. L., Carlton, A. M. G., Hayes, P. L., Liu, S., Ng, N. L., Russell, L. M., Setyan, A., Xu, L., Young, J., Zaveri, R. A., Zhang, Q., and Pye, H. O. T.: Semivolatile POA and parameterized total combustion SOA in CMAQv5.2: impacts on source strength and partitioning, Atmospheric Chemistry and Physics, 17, 11107-11133, https://doi.org/10.5194/acp-17-11107-2017, 2017.
Petters, M. D. and Kreidenweis, S. M.: A single parameter representation of hygroscopic growth and cloud condensation nucleus activity, Atmospheric Chemistry and Physics, 7, 1961-1971, https://doi.org/10.5194/acp-7-1961-2007, 2007.
Pye, H. O. T., Murphy, B. N., Xu, L., Ng, N. L., Carlton, A. G., Guo, H., Weber, R., Vasilakos, P., Appel, K. W., Budisulistiorini, S. H., Surratt, J. D., Nenes, A., Hu, W., Jimenez, J. L., Isaacman-VanWertz, G., Misztal, P. K., and Goldstein, A. H.: On the implications of aerosol liquid water and phase separation for organic aerosol mass, Atmospheric Chemistry and Physics, 17, 343-369, https://doi.org/10.5194/acp-17-343-2017, 2017.
Pye, H. O. T., D. J. Luecken, L. Xu, C. M. Boyd, N. L. Ng, K. Baker, B. A. Ayres, J. O. Bash, K. Baumann, W. P. L. Carter, E. Edgerton, J. L. Fry, W. T. Hutzell, D. Schwede, P. B. Shepson, Modeling the current and future roles of particulate organic nitrates in the southeastern United States, https://doi.org/10.1021/acs.est.5b03738, Environmental Science & Technology, 2015.
Pye, H. O. T., R. W. Pinder, I. Piletic, Y. Xie, S. L. Capps, Y.-H. Lin, J. D. Surratt, Z. Zhang, A. Gold, D. J. Luecken, W. T. Hutzell, M. Jaoui, J. H. Offenberg, T. E. Kleindienst, M. Lewandowski, and E. O. Edney, Epoxide pathways improve model predictions of isoprene markers and reveal key role of acidity in aerosol formation, Environmental Science & Technology, https://doi.org/10.1021/es402106h, 2013.
Pye, H. O. T., Chan, A. W. H., Barkley, M. P., and Seinfeld, J. H.: Global modeling of organic aerosol: the importance of reactive nitrogen (NOx and NO3), Atmospheric Chemistry and Physics, 10, 11261-11276, https://doi.org/10.5194/acp-10-11261-2010, 2010.
Qin, M., Murphy, B. N., McDonald, B. C., McKeen, S. A., Koval, L., Isaacs, K., Lu, Q., Robinson, A. L., Strum, M., Snyder, J., Efstathious, C., Allen, C., and Pye, H. O. T.: The estimated impacts of volatile chemical products on particulate matter and ozone criteria pollutants in an urban atmosphere, in preparation.
Xu, L., Pye, H. O. T., He, J., Chen, Y., Murphy, B. N., and Ng, N. L.: Experimental and model estimates of the contributions from biogenic monoterpenes and sesquiterpenes to secondary organic aerosol in the southeastern United States, Atmospheric Chemistry and Physics, 18, 12613-12637, https://doi.org/10.5194/acp-18-12613-2018, 2018.
[PR #346, 341, 353, 335]