Simulating isoprene oxidation in GFDL AM3 model

1. Simulating isoprene oxidation in GFDL AM3 model Jingqiu Mao (NOAA GFDL), Larry Horowitz (GFDL), VaishaliNaik (GFDL), Meiyun Lin (GFDL), Arlene Fiore (Columbia U) Funding from NOAA CPO

2. Summertime ozone over eastern US is a problem for most models Northeast US Standard AM3 Multimodel mean Obs from CASTNET surface sites Southeast US Multimodel mean Obs from CASTNET surface sites (Naik et al., 2013, JGR, in press) (Fiore et al., 2009, JGR)

3. A new isoprene chemistry for global models ISOPO2 + NO is based on Paulot et al. (2009, ACP). ISOPO2 + HO2 is based on Paulot et al. (2009, Science). Isomerization of ISOPO2 is based on Peeters et al. (2009, PCCP) and Crounse et al. (2011, PCCP) . How fast is the isomerization? (Mao et al., submitted to JGR)

4. Was OH really that high over SE US during ICARTT? A new method of measuring OH was deployed in Blodgett Forest OH measured by traditional method during ICARTT 2004 (Ren et al., 2008, JGR) (Mao et al., 2012, ACP) Part of OH signal could be due to interference, probably from Criegee Intermediate!

5. First generation of isoprene nitrates degraded to second generation nitrates! First generation isoprene nitrates (C5) C5 alkyl nitrate is short-lived due to oxidation by OH and ozone, with photochemical lifetime of 2-3 hrs. Consistent with measurements from Thornton’s group, C5<< C4. Second generation isoprene nitrates (C3-C4)

6. Nighttime chemistry Based on Rollins et al. (2009) and Xie et al. (2012) Nighttime yield of organic nitrates is 70%>> daytime yield (11.7%)

7. This chemistry was implemented in GEOS-Chem Ozone in the boundary layer during ICARTT 2004 Model Observations Obs vs. Model Improved O3-CO correlations due to: Recycling of NOx from isoprene nitrates HO2 uptake (lower OH and increase NOx lifetime). (Mao et al., submitted to JGR)

8. Observations Model (GEOS-Chem) Mean vertical profiles during ICARTT O3 has no bias in boundary layer and free troposphere. HCHO provides good constraint on isoprene emissions. (Mao et al., submitted to JGR)

9. Total organic nitrates excluding peroxyacylnitrates (∑ANs) Vertical profiles Speciation of ∑ANs Model well reproduced ∑ANs. ∑ ANs is dominated by secondary organic nitrates (C3-C4). ∑ANs vs. HCHO ∑ANs vs. O3 Model well reproduced ∑ANs vs. HCHO and ∑ANs vs. O3 correlations. These correlations cannot be reproduced by a fast isomerization channel of ISOPO2.

10. NOy budget in eastern U.S. boundary layer for July 2004 Export of ∑ANs > Export of PANs

11. Surface ozone response to isoprene emissions NOx emissions↓ Sensitivity of ozone to isoprene emissions ↓ New chemistry Isoprene↑ NOx ↓ OH ↓ O3 ↓ due to O3+ISOP Previous studies without NOx recycling Reduce current anthroNOx emissions by 50% Current anthroNOxemissions (2004)

12. GFDL AM3 configuration for SENEX • Fully coupled chemistry-climate model • Parameterizes aerosol activation into liquid cloud droplets • solves both tropospheric and stratospheric chemistry over the full domain • Nudging wind with GFS meteorological field • High resolution (50 x 50 km) and coarse resolution (200 x 200 km) • MEGAN biogenic emissions • Anthropogenic emissions use RCP 8.5 scenario (0.5 x 0.5 degree) • New isoprene chemistry (Mao et al., submitted to JGR) • New heterogeneous chemistry (Mao et al., 2013a, ACP; 2013b, GRL) C180 (50 x 50km) C48 (200 x 200km) Monthly mean ozone for July of 2012

13. Updated chemistry Standard AM3 Observations CASTNET sites

14. Improvement on ozone over SE US Standard AM3 New chemistry in AM3 (Naik et al., 2013, JGR, in press) • Bias is reduced from 12.9 ppbv to 3.3 ppbv. • This should be reexamined by MDA8 ozone. Model tends to overestimate monthly mean ozone.

15. Does nighttime chemistry affect global nitrogen/ozone budget? Sunset Sunrise Model shows large amount of VOCs and OVOCs in the residual layer. Is it possible to do a early morning flight to see the entrainment zone? Entrainment zone Boundary layer structure by Stull (1988).

16. HCHO yield at different NOx conditions Computed in a photochemical box model. Initialized with 1ppb isoprene. O3 (40ppb), CO (100ppb), and NOx are held constant. Prompt HCHO formation, important for deriving isoprene emission from satellite observations. Yield of HCHO is lower at lower NOx concentrations, according to the model. But the model could be wrong!

17. Next step: merging in-cloud SOA module with new isoprene chemistry A new module of in-cloud SOA production developed in AM3 (Liu et al., 2012, JGR) (Ford et al., 2013, ACPD)

18. Surface NOxventilation will be critical for NOx/ozone in free trop (Lamsal et al., 2010) Surface NOx emissions >> other emissions above the surface. 10% leak of surface NOx will double the effect of lightning.

19. Observed ventilation from LIDAR (aerosol profiles Jul. 3, 2001, Barcelona, Campus Nord, UPC)!