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Two puzzles of atmospheric chemistry over the Southeast US

Two puzzles of atmospheric chemistry over the Southeast US. Jingqiu Mao (AOS/GFDL) , Larry Horowitz (GFDL), Vaishali Naik (GFDL), Fabien Paulot (Harvard), Paul Ginoux (GFDL), Meiyun Lin (GFDL), Arlene Fiore (Columbia U) and the SENEX science team. Funding from NOAA CPO.

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Two puzzles of atmospheric chemistry over the Southeast US

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  1. Two puzzles of atmospheric chemistry over the Southeast US Jingqiu Mao (AOS/GFDL), Larry Horowitz (GFDL), VaishaliNaik (GFDL), Fabien Paulot (Harvard), Paul Ginoux(GFDL), Meiyun Lin (GFDL), Arlene Fiore (Columbia U) and the SENEX science team Funding from NOAA CPO

  2. What is so unique for Southeast US? Anthropogenic + Natural HCHO is mainly produced from biogenic emissions (isoprene in particular) Surface NOx is mainly produced from anthropogenic activities (Martin et al., 2008, AE) (Millet et al., 2008, JGR)

  3. Volatile organic compounds (VOCs) in the atmosphere:carbon oxidation chain Importance of NOx • sources of organic aerosol • sources/sinks of oxidants (ozone, OH) Increasing functionality & cleavage h O3 OH + products NO2 h OH R’O2 carbonyls NO organic aerosol OH VOC RO2 HO2 organic peroxy radicals OH,h ROOH products organic peroxides biosphere combustion industry OVOCs deposition EARTH SURFACE

  4. Global Budget of Organic Aerosols Global sources in Tg C y-1 20 K OH, O3,NO3 SOG SOA VOC Two-product ? POA Aqueous reactions isoprene terpenes oxygenates… ? 50 Uptake on cloud droplets or aerosols 20 100 700 alkenes aromatics oxygenates… 30 vegetation fuel/industry open fires fuel/industry open fires VOC EMISSION PRIMARY EMISSION SOA ≡ secondary organic aerosol POA ≡ primary organic aerosol Current AM3 treats SOA production as yield of terpene emissions.

  5. Puzzle 1: Overestimate of ozone

  6. 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)

  7. Similar bias was found for the maximum daily 8-hour average ozone comparison. Overestimate of ozone is likely a chemistry problem Previous models with assimilated meteorology field (CTM) show similar overestimate. Models with higher resolution also show similar overestimate. Fiore et al. (2005) attributed this bias to the treatment of isoprene chemistry in the model. (Rasmussen et al., 2012, AE)

  8. Puzzle 2 : Aerosols and regional cooling

  9. Temperature trend over past century 1950-2006 for May-June (Unit: K/Decade) 1930-1990 change in Annual Mean Surface Temperature (Leibensperger et al., 2012, ACP) This temperature trend cannot be explained by the change in precipitation or dynamic patterns (El Niňo, NAO) (Portmann et al., 2009). (Portmannet al., 2009, PNAS)

  10. The cooling can be partially due to secondary organic aerosols MISR aerosol optical thickness (diff. between JJA and DJF) MODIS aerosol optical thickness (diff. between JJA and DJF) (Ford et al., 2013, ACPD) Current hypothesis is that large amount of organic aerosols are produced above the surface layer. (Goldstein et al., PNAS, 2009)

  11. Similar problem was found in GFDL models Optical properties from aircraft data (left) and the model (right) over Oklahoma, US CM 2.1 CM 3 Model cannot reproduce high loading of aerosols above the surface layer! (Courtesy of Paul Ginoux and Ilissa Ocko)

  12. Surface Air Temperature Years (1961-2000) minus (1881-1920) OBS (GISS) CM2.1 CM3 K (Courtesy of Larry Horowitz) Stronger cooling at northern mid-latitudes in CM3, 3x less warming globally  examine forcings

  13. Underestimate of organic aerosol is also a chemistry problem (Ford et al., 2013, ACPD) Current models cannot reproduce such amount of aerosols above the surface layer. This cannot be explained by PBL height, SO2 emissions.

  14. New development of chemistry in AM3: (1) heterogeneous chemistry

  15. A new framework for heterogeneous chemistry Standard AM3 N2O5, HO2 SO4 Hygroscopic growth factor Updated AM3 N2O5, HO2, NO3, NO2 SO4 OC BC dust SeaSalt (Mao et al., 2013a, ACP; 2013b, GRL)

  16. Impact of heterogeneous chemistry (AM3 C48 2001-2005) Simulation (het chem on) – Simulation (het chem off) (Mao et al., 2013a, ACP; 2013b, GRL)

  17. Improvement on CO at 500 hPa Improvement on OH ratio (NH/SH) MOPITT AM3 with het chem off obs AM3 with het chem on (Naiket al., 2013, JGR, in press) MOPITT (2000-2004) AM3(2001-2005)

  18. The impact of biomass burning emissions on global OH/ozone: Implications for radiative forcing IPCC AR4 only estimates the direct forcing from biomass burning aerosols (+0.03 ±0.12 W m-2)

  19. Aerosol uptake has large impact on ozone production efficiency Observations ΔO3/ΔCO is a measure of ozone production efficiency.

  20. Sensitivity of tropospheric oxidants to biomass burning emissions Global OH decreases with larger bb emissions. Global ozone increases with larger bb emissions.

  21. Nonlinearity of total radiative forcing on biomass burning strength Chemical indirect forcing from CH4and CH4-induced changes in O3 and stratospheric H2O, is comparable to the cooling from biomass burning aerosols with direct and indirect effect taken into account. Steady state CH4 CH4-induced O3 and H2O How about chemical indirect forcing from anthropogenic emissions? (Mao et al., 2013b, GRL)

  22. New development of chemistry in AM3: (2) a new isoprene chemistry scheme

  23. A new isoprene oxidation mechanism for global models OH recycling from isoprene oxidation has been a hot topic in atmospheric chemistry community in last 5 years! (Mao et al., submitted to JGR)

  24. 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 biogenic VOC oxidation products!

  25. 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. Second generation isoprene nitrates (C3-C4) (Paulot et al., 2009a,b)

  26. NOy budget in eastern U.S. boundary layer for July 2004 Export of ∑ANs > Export of PANs Organic compounds may have much larger impact on global nitrogen cycling than previously thought! Funded by NOAA CPO program, titled “Impact of organic nitrate chemistry on air quality and climate: past, present and future atmospheres” for 2013-2016.

  27. Surface ozone response to isoprene emissions: Implications for future air quality NOx emissions↓ Sensitivity of ozone to isoprene emissions ↓ New chemistry Isoprene↑ NOx ↓ OH ↓ O3 ↓ due to O3+ISOP Previous studies without NOx recycling AnthroNOx emissions in 2004 Reduce anthroNOx emissions of 2004 by 50% (Mao et al., submitted to JGR)

  28. NOx emissions has been reduced by 34% from 2005 to 2011 OMI NO2 column in 2005 (summer) OMI NO2 column in 2011 (summer) difference (Russell et al. 2012, ACP)

  29. AM3 with updated chemistry

  30. Updated chemistry Standard AM3 Observations CASTNET sites

  31. Improvement on ozone over SE US Standard AM3 New chemistry in AM3 (Naik et al., 2013, JGR, in press) (C48 2001-2005) • 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.

  32. Field studies over Southeast US in this summer SENEX (NOAA) Two aircrafts based at Smyrna, TN and a tower located at Centerville, Alabama. Measurements include VOC, NOx, ozone, aerosols, CCN etc. GFDL will submit C180 nudge simulations to SENEX data archive. A modeling workshop to be held in Rutgers U. NOMADSS (NCAR) SOAS (NSF & EPA)

  33. 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 (process-based emission) • Anthropogenic emissions use RCP 8.5 scenario (0.5 x 0.5 degree) • New heterogeneous chemistry (Mao et al., 2013a, ACP; 2013b, GRL) • New isoprene chemistry (Mao et al., submitted to JGR) C180 (50 x 50km) C48 (200 x 200km) Monthly mean ozone for July of 2012

  34. Model of Emission of Gases and Aerosols from Nature (MEGAN) • Process-based emission inventory Leaf age Leaf Area Index Temperature dependence Light dependence Fractional coverage Emission factor

  35. Preliminary results from aircraft observations and AM3 C180 nudging simulation HCHO measurements in boundary layer for all flights in June Monthly mean surface HCHO concentrations for June of 2012

  36. Model does not show ozone bias. Model shows good agreement with HCHO. One flight on June 03, 2013 Flight altitude HCHO (obs vs. model) Ozone (obs vs. model) Time Time

  37. AM3 simulations on SENEX campaign Question: What are the formation mechanisms of secondary species (ozone, sulfate and organics) in the SE U.S.? Evaluate anthropogenic and biogenic emissions in AM3 over southeast US (aircraft, model and satellite). Evaluate model simulation of ozone, SOA precursors from aircraft and ground measurements. Implement a new module of in-cloud SOA processing from Liu et al. (2012). Evaluate organic aerosol simulations (organic aerosols in particular) and its implications for future and past atmosphere. A new module of in-cloud SOA production developed in AM3 (Liu et al., 2012, JGR) The “role of aerosols in regional climate” was recently identified as an important crosscutting research challenge for NOAA in the report “Toward Understanding and Predicting Regional Climate Variations and Change”.

  38. Conclusions We implemented a new set of chemistry in AM3, which significantly improves model simulation of ozone over SE US. This updated chemistry show significant impact on global OH, CO, O3, nitrogen cycling, and have important implications on predicting future climate change and air quality. GFDL is participating NOAA SENEX campaign with C180 nudging model. Overestimate of ozone (puzzle 1) may be significantly improved from this study Underestimate of organic aerosols (puzzle 2) can be at least partly improved in the model.

  39. 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).

  40. 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!

  41. Two new pathways for SOA formation Cloud evaporates Aqueous reactions in cloud droplets SOA Direct uptake of organic compounds by aerosols SO4 SOA precursors (Glyoxal, methyl glyoxal etc.) OC SOA BC BVOCs NOx Current limitation: We have no constraints on these SOA precursors.

  42. Tropospheric ozone chemistry Air Quality O2 hn O3 STRATOSPHERE Climate 8-18 km TROPOSPHERE hn NO2 NO O3 hn, H2O OH HO2 CH4,CO, VOCs Deposition

  43. Annual average aerosol loading from IMPROVE site Ammonium sulfate Organic aerosols Surface measurements show low fraction of organic aerosols

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

  45. 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)

  46. 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)

  47. 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.

  48. SENEX 2013 field campaign Southeast Nexus Studying the Interactions Between Natural and Anthropogenic Emissions at the Nexus of Climate Change and Air Quality Where: Southeast U.S. When: Summer 2013 What: The focus of NOAA's field study includes GFDL modeling and ESRL CSD measurements using the NOAA WP-3D aircraft. Who: Investigators in this project include researchers from several universities, industries, and governmental agencies.

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