1. Constraining methane emissions in North America
Towards a Global Carbon Observing System: Progresses and Challenges
Geneva, 1-2 October 2013
Constraining methane emissions in North America
by high-resolution inversion of satellite data:
from SCIAMACHY to GOSAT and beyond
Daniel Jacob, Kevin Wecht, AlexTurner, Melissa Sulprizio

2. Methane emission inventories for N. America:
EDGAR 4.2 (anthropogenic), Kaplan (wetlands)
N American totals in Tg a-1
Surface/aircraft observations in US suggest 2-3x underestimate of emissions

3. Methane observing system in North America
Satellites
Thermal IR
AIRS, TES, IASI
SCIAMACHY
6-day
GOSAT
3-day, sparse
TROPOMI GCIRI (?)
1-day geo
Shortwave IR
Suborbital
1/2ox2/3o grid of GEOS-Chem chemical transport model (CTM)
INTEX-A
SEAC4RS
CalNex

4. GEOS-Chem CTM and its adjoint nested in 4ox5o global domain
Use GEOS-Chem CTM with observing system
for optimized estimate of methane emissions
EDGAR Kaplan
a priori bottom-up emissions
Observations
GEOS-Chem CTM and its adjoint
1/2ox2/3o over N. America
nested in 4ox5o global domain
Bayesian
inversion
Validation
Verification
Optimized emissions
at 1/2ox2/3o resolution

5. Testing GEOS-Chem methane background
with HIPPO aircraft data across Pacific
Aug-Sep11
Jan09
Oct-Nov09
Jun-Jul11
GEOS-Chem
HIPPO
Methane, ppbv
Latitude, degrees
Boundary conditions for N. American window
are optimized as part of the inversion
Alex Turner and Kevin Wecht, Harvard

6. 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 XCH4
INTEX-A methane below 850 hPa
C. Frankenberg
(JPL)
D. Blake
(UC Irvine)
XCH4
INTEX-A validation profiles
H2O correction to SCIAMACHY data
SCIAMACHY
Kevin Wecht, Harvard
INTEX-A

7. Optimization of state vector for adjoint inversion of SCIAMACHY data
Optimal clustering of 1/2ox2/3o gridsquares
Native resolution clusters
Correction factor to bottom-up emissions
Number of clusters in inversion
,000 34 28
Optimized US anthropogenic emissions (Tg a-1)
posterior cost function
SCIAMACHY data cannot constrain
emissions at 1/2ox2/3o resolution;
use 1000 optimally selected clusters
Kevin Wecht, Harvard

8. N. American methane emission estimates
optimized by SCIAMACHY data (Jul-Aug 2004)
SCIAMACHY column methane mixing ratio
Correction factors to priori emissions
1700
1800
ppb
US anthropogenic emissions (Tg a-1)
EDGAR v
EPA
This work
Kevin Wecht, Harvard

9. GOSAT methane column mixing ratios, Oct 2009-2010
Retrieval from U. Leicester

10. Preliminary global adjoint inversion
of GOSAT Oct methane data
Correction factors to prior emissions (EDGAR Kaplan)
Nested adjoint inversion
with 1/2ox2/3o resolution
Alex Turner, Harvard

11. Testing information content of satellite data
with CalNex inversion of methane emissions
CalNex observations
with GEOS-Chem prior
Correction factors to EDGAR v4.2
May-Jun
2010
1800
2000
ppb
2x underestimate
of livestock emissions
Emisssions, Tg a-1
Kevin Wecht, Harvard

12. GOSAT observations are too sparse
for spatial resolution of California emissions
Correction factors to methane emissions from inversion
GOSAT data (CalNex period))
GOSAT (CalNex period) GOSAT (1 year)
Each point =
1-10 observations
0.5
1.5
CalNex
aircraft data
GOSAT
(CalNex)
(1 year)
Degrees of Freedom for Signal (DOFS)
in inversion of methane emissions
14.7
0.55
1.41
Kevin Wecht, Harvard

13. Potential of TROPOMI and GCIRI for constraining methane emissions
Correction factors to EDGAR v4.2 a priori emissions from a 1-year OSSE
TROPOMI (global daily coverage) GCIRI (geostationary 1-h return coverage)
A priori
CalNex
TROPOMI
GCIRI
TROPOMI+GCIRI
DOFS
14.7
9.5
14.1
16.7
California emissions (Tg a-1)
1.9
3.2
2.9
3.0
3.1
Kevin Wecht, Harvard

14. Working with stakeholders at the US state level
State-by-state analysis of SCIAMACHY correction factors to bottom-up 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

15. Policy-relevant recommendations
for monitoring N American methane emissions
Need better understanding of methane emissions from livestock; these seem to be seriously underestimated in US EPA emission inventory
No apparent underestimate of methane emissions from oil/gas production, but careful monitoring is needed in view of industry expansion
TROPOMI (2015 launch) holds considerable promise for monitoring methane emissions; need to prepare inverse methods for exploiting the data
GCIRI (proposed geostationary launch in 2018/2019) would greatly augment capability for methane monitoring
Ground measurement sites play a critical role in evaluating satellite data; targeted aircraft campaigns can provide verification and better understanding of source regions