Current work on methane and tropospheric bromine Daniel J. Jacob with Kevin Wecht, Alex Turner, Melissa Sulprizio, Johan Schmidt

Global methane trend (IPCC AR5) UCI AGAGE NOAA

Building a methane monitoring system for N America EDGAR emission Inventory for methane Can we use satellites together with suborbital observations of methane to monitor methane emissions on the continental scale and test/improve emission inventories?

Methane emission inventories for N. America: EDGAR 4.2 (anthropogenic), LPJ (wetlands) N American totals in Tg a -1 Previous top-down constraints from surface/aircraft observations have suggested factor of 2-3 underestimate in US emissions

AIRS, TES, IASI Methane observing system in North America Satellites Thermal IR SCIAMACHY 6-day GOSAT 3-day, sparse TROPOMI GCIRI 1-day geo Shortwave IR Suborbital CalNex INTEX-A SEAC 4 RS 1/2 o x2/3 o grid of GEOS-Chem chemical transport model (CTM)

High-resolution inverse analysis of methane emissions in North America GEOS-Chem CTM and its adjoint 1/2 o x2/3 o over N. America nested in 4 o x5 o global domain Observations Bayesian inversion Optimized emissions at 1/2 o x2/3 o resolution Validation Verification EDGAR LPJ a priori bottom-up emissions

Testing GEOS-Chem methane background with HIPPO aircraft data across Pacific GEOS-Chem HIPPO Latitude, degrees Jan09 Oct-Nov09Jun-Jul11 Aug-Sep11 Alex Turner and Kevin Wecht, Harvard Time-dependent boundary conditions are optimized iteratively as part of the inversion Methane, ppbv

Optimization of methane emissions using SCIAMACHY data for Jul-Aug 2004 Concurrent INTEX-A aircraft mission allows validation of SCIAMACHY, evaluation of inversion SCIAMACHY column methane mixing ratio X CH4 INTEX-A methane below 850 hPa INTEX-A validation profiles H 2 O correction to SCIAMACHY data Kevin Wecht, Harvard D. Blake (UC Irvine) C. Frankenberg (JPL) SCIAMACHY INTEX-A X CH4

Optimized selection of emission clusters for adjoint inversion of SCIAMACHY data Optimal clustering of 1/2 o x2/3 o gridsquares Correction factor to bottom-up emissions Number of clusters in inversion , Optimized US anthropogenic emissions (Tg a -1 ) posterior cost function Native resolution 1000 clusters SCIAMACHY data cannot constrain emissions at 1/2 o x2/3 o resolution; use 1000 optimally selected clusters Kevin Wecht, Harvard

North American methane emission estimates optimized by SCIAMACHY data (Jul-Aug 2004) ppb SCIAMACHY column methane mixing ratio Correction factors to priori emissions US anthropogenic emissions (Tg a -1 ) EDGAR v EPA 28.3 This work 32.7 Kevin Wecht, Harvard

GOSAT methane column mixing ratios, Oct Retrieval from U. Leicester

Preliminary inversion of GOSAT Oct methane Nested inversion with 1/2 o x2/3 o resolution Correction factors to prior emissions (EDGAR LPJ) Alex Turner, Harvard Next step: clustering of emissions in the inversion

Testing the information content of satellite data with CalNex inversion of methane emissions CalNex observationsGEOS-Chem w/EDGAR v Correction factors to EDGAR (analytical inversion) ppb May-Jun 2010 Emisssions, Tg a -1 Kevin Wecht, Harvard 2x underestimate of livestock emissions S. Wofsy (Harvard)

GOSAT observations are too sparse to spatially resolve California emissions GOSAT data (CalNex period)) Correction factors to methane emissions from inversion GOSAT (CalNex period) GOSAT (1 year) CalNex aircraft data GOSAT (CalNex) GOSAT (1 year) Degrees of Freedom for Signal (DOFS) in inversion of methane emissions Each point = 1-10 observations Kevin Wecht, Harvard

Potential of TROPOMI and GCIRI for constraining methane emissions TROPOMI (global daily coverage) GCIRI (geostationary 1-h return coverage) Correction factors to EDGAR v4.2 a priori emissions from a 1-year OSSE A prioriCalNexTROPOMIGCIRITROPOMI+GCIRI DOFS California emissions (Tg a -1 ) Kevin Wecht, Harvard

Working with stakeholders at the US state level State-by-state analysis of SCIAMACHY correction factors to EDGARv4.2 emissions with Iowa Dept. of Natural Resources State emissions computed w/EPA tools too low by x3.5; now investigating EPA livestock emission factors with New York Attorney General Office State-computed emissions too high by x0.6, reflects overestimate of gas/waste/landfill emissions Melissa Sulprizio and Kevin Wecht, Harvard Hog manure? Large EDGAR source from gas+landfills is just not there correction factor

Now on to bromine…

Bromine chemistry in the atmosphere Tropopause (8-18 km) Troposphere Stratosphere Halons CH 3 Br CHBr 3 CH 2 Br 2 Sea salt BrBrO BrNO 3 HOBrHBr O3O3 hv, NO hv OH Inorganic bromine (Br y ) Br y OH, h debromination deposition industryplankton Stratospheric BrO: 2-10 ppt Tropospheric BrO: ppt Thule GOME-2 BrO columns Satellite residual [Theys et al., 2011] BrO column, cm -2 VSLS

Mean vertical profiles of CHBr 3 and CH 2 Br 2 From NASA aircraft campaigns over Pacific in April-June Vertical profiles steeper for CHBr 3 (mean lifetime 21 days) than for CH 2 Br (91 days), steeper in extratropics than in tropics Parrella et al. [2012]

Model comparison to HIPPO organobromine data No bias for CHBr 3, CH 3 Br; 10% low bias for CH 2 Br 2 Johan Schmidt, Harvard CHBr 3 CH 2 Br 2 CH 3 Br Observed GEOS-Chem

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) Br y 3.2 ppt 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]

Tropospheric Br y cycling in GEOS-Chem Gg Br [ppt] Global annual mean loadings in Gg Br [ppt], rates in Gg Br s -1 Model includes HOBr+HBr in aq aerosols with  = 0.2, ice with  = 0.1 Mean daytime BrO = 0.6 ppt; would be 0.3 ppt without HOBr+HBr reaction Parrella et al. [2012]

Comparison to seasonal satellite data for tropospheric BrO [Theys et al., 2011] model TOMCAT has lower  =0.02 for HOBr+HBr than GEOS-Chem, large polar spring source from blowing snow HOBr+HBr reaction critical for increasing BrO with latitude, winter/spring NH max in GEOS-Chem (9:30 am) Parrella et al. [2012]

Effect of Br chemistry on tropospheric ozone Zonal mean ozone decreases (ppb) in GEOS-Chem Two processes: catalytic ozone loss via HOBr, NO x loss via BrNO 3 Global OH also decreases by 4% due to decreases in ozone and NO x Parrella et al. [2012]

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 Model BrO is similar in pre-industrial and present atmosphere (canceling effects) Parrella et al. [2012]

Atmospheric lifetime of Hg(0) against oxidation to Hg(II) by Br Hg(0) + Br ↔ Hg(I) → Hg(II) Br,OH 2-step Hg(0) oxidation (Goodsite et al., 2004; Donohoue et al., 2006) Emission Deposition GEOS-Chem Br yields Hg(0) global mean tropospheric lifetime of 4 months, consistent with observational constraints Br in pre-industrial atmosphere was 40% higher than in present-day (less ozone), implying a pre-industrial Hg(0) lifetime of only 2 months  Hg could have been more efficiently deposited to northern mid-latitude oceans in the past Parrella et al. [2012]

More recent model comparisons to BrO observations TORERO - CU AMAX-DOAS over the SE Pacific (R. Volkamer, CU Boulder) OMI tropospheric BrO from cloud slicing (S. Choi, SSAI/NASA GSFC) Johan Schmidt, Harvard Upper tropospheric BrO is severely underestimated by GEOS-Chem: major implications for tropospheric ozone, Hg Observations GEOS-Chem MAM DJF

Model vs. observed ozone in upper troposphere TORERO HIPPO Model doesn’t underestimate ozone transport from stratosphere -but stratospheric Br y /O 3 ratio could still conceivably be too low Johan Schmidt, Harvard

Model vertical profiles over SE Pacific Altitude, km HBr, BrNO 3 are major reservoirs in upper troposphere; should they cycle more efficiently to radicals? Johan Schmidt, Harvard

Heterogeneous bromine chemistry currently in GEOS-Chem to be included in GEOS-Chem Johan Schmidt, Harvard Can heterogeneous chemistry correct the model underestimate of BrO in UT? Stay tuned! Any other ideas?