Future directions in tropospheric chemistry – what else besides climate change Daniel J. Jacob Group photo (2013)

Range of tropospheric chemistry problems LOCAL < 100 km REGIONAL km GLOBAL > 1000 km Urban smog Plume dispersion Disasters Visibility Regional smog Acid rain Ozone layer Climate Biogeochemical cycles CLIMATE!

Range of tropospheric chemistry problems LOCAL < 100 km REGIONAL km GLOBAL > 1000 km Urban smog Plume dispersion Disasters Visibility Regional smog Acid rain Ozone layer Biogeochemical cycles

Jennifer’s foray into ozone smog Nitrogen oxides in the troposphere: global and regional budgets (Logan, 1983) – 508 citations The sensitivity of ozone to nitrogen oxides and hydrocarbons in regional ozone episodes (Sillman, Logan, Wofsy, 1990) -283 citations Ozone in rural areas of the United States (Logan, 1989) citations Factors regulating ozone over the United States and its export to the global atmosphere (Jacob, Logan, et al. 1993) – 150 citations This report paved the way for NO x controls! (1991)

Trend in 95 th percentile daytime ozone, Spring Summer Cooper et al. [2012] Decrease in eastern US driven by NO x emission controls; Increase or flat in Intermountain West

4 th -highest annual maximum for daily 8-h average ozone, Intermountain West: The next ozone frontier! Current standard: 75 ppb Proposed standard: ppb

Surface ozone at Gothic, Colorado Most ozone originates from outside N America Peak events of stratospheric influence cannot be reproduced by model Zhang et al., in prep. Numerical decay of a free tropospheric plume In GEOS-Chem Eulerian models have difficulty preserving gradients (layers) in divergent free tropospheric flow, in a way that cannot be readily fixed by increasing grid resolution or the accuracy of numerical scheme Rastigeyev et al. [2010]

Ammonia emission and air pollution Observed NH 4 + wet deposition fluxes can constrain NH 3 emission estimates NADP data (circles) and GEOS-Chem model after adjoint inversion April: fertilizer July: livestock kgN ha -1 month -1 Contribution of food export to annual PM 2.5 (ammonium nitrate) GEOS-Chem sensitivity simulation Fabien Paulot (in prep.)

Critical load exceedances for N deposition at US national parks Ellis et al. [2013] More deposition is expected to originate from ammonia in future Critical loads are 3-5 kg N ha -1 a -1 depending on ecosystem NO x NH 3 Present and future (RCP) US emissions Future exceedances driven by ammonia emissions Ellis et al. [2013] RCP2.6

Next frontier for air pollution: Nigeria OMI formaldehyde MISR SCIA aerosol (AOD) NO 2 HCHO glyoxal methane Population: 270 million (+2.6% a -1 ) GDP: $273 billion (+7% a -1 ) – oil! Most natural gas is flared >80% of domestic energy from biofuel, waste Lagos Port Harcourt An unusual mix of very high VOCs, low NO x – What will happen as infrastructure develops? Eloise Marais [Harvard] gas flaring!

Biogeochemical cycle of mercury Hg(0) Hg(II) particulate Hg burial SEDIMENTS uplift volcanoes erosion oxidation Hg(0)Hg(II) reduction biological uptake ANTHROPOGENIC PERTURBATION: fuel combustion mining ATMOSPHERE OCEAN/SOIL VOLATILE WATER-SOLUBLE (months)lifetime ~6 months

History of global anthropogenic Hg emissions Large past (legacy) contribution from N. American and European emissions; Asian dominance is a recent phenomenon Streets et al., 2011

Global source contributions to Hg in present-day surface ocean Human activity has increased 7x the Hg content of the surface ocean Half of this human influence is from pre-1950 emissions N America, Europe and Asia share similar responsibilities for anthropogenic Hg in present-day surface ocean Amos et al., in press Europe Asia N America S America former USSR ROW pre-1850 natural emissions from biogeochemical box model constrained with GEOS-Chem fluxes

Disposal of Hg in commercial products: a missing component of the Hg biogeochemical cycle? Global production of commercial Hg peaked in 1970 Hannah Horowitz (Harvard)

Global tropospheric Br y budget in GEOS-Chem (Gg Br a -1 ) SURFACE CHBr CH 2 Br 2 57 CH 3 Br Marine biosphere Sea-salt debromination (50% of 1-10 µm particles) STRATOSPHERE TROPOSPHERE 7-9 ppt Liang et al. [2010] stratospheric Bry model (upper boundary conditions) Volcanoes (5-15) Deposition lifetime 7 days 1420 Sea salt is the dominant global source but is released in marine boundary layer where lifetime against deposition is short; CHBr 3 is major source in the free troposphere Parrella et al. [2012] Br y 3.2 ppt BrO 0.32 ppt

Bromine chemistry improves simulation of 19 th century surface ozone Standard models without bromine are too high, peak in winter-spring; bromine chemistry corrects these biases Implies that anthropogenic perturbation to global tropospheric ozone is larger than currently assumed Parrella et al. [2012]

Elusive understanding of what controls tropospheric OH GEOS-Chem with climatological lightning GEOS-Chem with interannual lightning (LIS) Lightning seems to be a major driver of OH variability (Murray, Logan, Jacob, 2013) LIS+OTD (satellite) lightning, Tropical lightning interannual variability

TEMPO geostationary UV/Vis satellite instrument selected in November 2012 for 2018 launch PI: Kelly Chance, Harvard-Smithsonian Monitoring of tropospheric ozone (2 levels), aerosols, NO 2, SO 2, formaldehyde, glyoxal with 1-hour temporal resolution, 2-km spatial resoution To be part of a geostationary constellation with other sensors observing Europe and East Asia TEMPO Sentinel-4 GEMS Next frontier in satellite observations of atmospheric composition!