PAN

Emily Fischer has updated the PAN simulation. The code has been merged with v9.02.h at this point, and a publication (Fischer et al., 2013) has been submitted to ACP.

Updates to Chemistry

1. I replaced the isoprene chemical mechanism with the Paulot scheme. This scheme has already been implemented into the standard code.

2. I added nighttime chemistry from reactions of organic peroxy radicals with NO3 following Stone et al. (2013). This may not be incorporated into the standard chemistry, and needs to be discussed by the GEOS-Chem Steering Committee.

3. I updated the rate coefficients for the reactions of HO2 with the >C2 peroxy radicals to Equation (iv) in Saunders et al. (2003). These changes have been incorporated into the standard code.

4. I added several new NMVOCs. The extended mechanism includes ethanol, benzene, toluene and ethylbenzene (lumped), xylenes and trimethyl benzenes(lumped), and monoterpenes (lumped). Hydroxyacetone and methylglyoxal, which are species in past versions, are treated as tracers in this simulation. Hydroxyacetone has a 1-2 day lifetime. Methylglyoxal is treated as a tracer so that it can be emitted from biomass burning plumes and so I could track PAN production via this pathway.

- The ethanol code was provided by Dylan Millet.

- The inclusion and treatment of aromatics was motivated by Liu et al. (2010). I calculated the associated yield of methylglyoxal using recommended values for the individual aromatic species(toluene, o-xylene, m-xylene, p-xylene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, and 1,3,5-trimethylbenzene) from Nishino et al. (2010) and the observed mean aromatic speciation for Chinese cities from Barletta et al. (2006). Thus the treatment is particular to the limited observations of aromatic speciation in China. It would be good to determine how different these ratios would be for the US, Europe or other developed/developing regions.

- We adopted the treatment of monoterpene oxidation from theRACM2 chemical mechanism (Goliff et al., 2013), lumping terpenes with one double bond (alpha-pinene, beta-pinene, sabinene and delta-3-carene) into one proxy. Unlike Ito et al. (2007), hydroxyacetone is not a product of terpene oxidation in the revised RACM2 mechanism used here. So I expect that the mechanism used here will make less PAN than that in Ito et al., 2007. This code was provided by Jingqiu Mao.

- I also added emissions of acetaldehyde from the ocean. This code was also provided by Dylan Millet.

5. I increased the deposition flux of PAN by assuming PAN reactivity with surfaces is more similar to O3 than NO2.