Havala O. T. Pye, U.S. Environmental Protection Agency
Monoterpene oxidation accounts for half the organic aerosol in the southeastern U.S. in summer, yet it is significantly underestimated in CMAQv5.2 with aero6 (Zhang et al. 2018). This update replaces the Odum 2-product monoterpene SOA in aero6 with updated yields based on more recent experiments by Saha and Greishop (2016). The new yields are represented using a volatility basis set (VBS) fit and applied to both OH and ozone oxidation of monoterpenes. The fit allows for prompt formation of low-volatility material, which is more consistent with recent observations. No additional chemistry, such as oligomerization, is applied to the prompt yields. This update was implemented in Xu et al. (2018) and additional information is available in their supporting information. Note that 7 VBS bins were used in the implementation of Xu et al. The highest volatility bin was not included in the CMAQ v5.3 implementation as it had very minor contributions to the SOA even under cold conditions with high loadings.
New Species: AMT1-6J, SVMT1-6
Deprecated species: ATRP1-2J, SV_TRP1-2
Significantly increases organic aerosol and dry PM2.5 mass, particularly in summer in the southeast U.S. Minor increases in mass occur at other times of year, including winter.
CCTM/src/aero/aero7 (linked to aero6)
deposition files
aero7 and aero7i mechanisms
Griffin, R. J., Cocker, D. R., Flagan, R. C., and Seinfeld, J. H.: Organic aerosol formation from the oxidation of biogenic hydrocarbons, Journal of Geophysical Research-Atmospheres, 104, 3555-3567, https://doi.org/10.1029/1998jd100049, 1999.
Saha, P. K. and Grieshop, A. P.: Exploring Divergent Volatility Properties from Yield and Thermodenuder Measurements of Secondary Organic Aerosol from α-Pinene Ozonolysis, Environmental Science & Technology, 50, 5740-5749, https://doi.org/10.1021/acs.est.6b00303, 2016.
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.
Zhang, H, et al.: Monoterpenes are the largest source of summertime organic aerosol in the southeastern United States, Proceedings of the National Academy of Sciences, 115, 2038-2043, https://doi.org/10.1073/pnas.1717513115, 2018
See aero7 overview