Atmosphere-based top-down emission estimates of HFC-134a and - - PowerPoint PPT Presentation

atmosphere based top down emission estimates of hfc 134a
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Atmosphere-based top-down emission estimates of HFC-134a and - - PowerPoint PPT Presentation

Atmosphere-based top-down emission estimates of HFC-134a and HCFC-22 from the U.S. over multiple years L. Hu 1,2 , S.A. Montzka 1 , J. Miller 1,3 , A.E. Andrews 1 , B.R. Miller 1,3 , S. Lehman 4 , K. Thoning 1 , C. Sweeney 1,3 , H. Chen 5,3


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SLIDE 1

Atmosphere-based “top-down” emission estimates of HFC-134a and HCFC-22 from the U.S.

  • ver multiple years
  • L. Hu1,2, S.A. Montzka1, J. Miller1,3, A.E. Andrews 1, B.R. Miller1,3, S.

Lehman4, K. Thoning1, C. Sweeney1,3, H. Chen5,3, K. Masarie1, L. Bruhwiler1, M.L. Fischer6, S.C. Biraud6, M.S. Torn6, E. Saikawa7, S. Miller8,

  • M. Mountain9, T. Nehrkorn9, J. Eluszkiewicz9, J.W. Elkins1, and P. Tans1

1 NOAA/ESRL/GMD, Boulder, Colorado, USA 2 NAS/NRC, Washington D.C., USA. 3 CIRES, U of Colorado, Boulder, Colorado, USA 4 INSTARR, U of Colorado, Boulder, Colorado, USA 5 CIO, University of Groningen, Groningen, The Netherlands 6 Lawrence Berkeley National Laboratory, California, USA 7 Environmental Sciences, Rollins School of Public Health, Emory University, Atlanta, GA, USA 8 Harvard University, Cambridge, MA, USA 9 AER, Lexington, MA, USA

Thanks to: A. Jacobson and S. Basu for inversion discussion, D. Godwin for providing EPA estimates and C. Siso, B. Hall and others involved with sampling, analysis, logistics, and program management. Funding in part from: NOAA’s Climate Program Office and its Atmospheric Chemistry, Carbon Cycle, and Climate Program, National Research Council.

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SLIDE 2

Goal:

  • To derive reliable “atmosphere-based” national emission estimates of
  • zone-depleting substances (ODSs) and greenhouse gases (GHGs)
  • To assess inventory-based “bottom-up” estimates

US Emission magnitudes? Seasonality & Inter-annual variability? Emission trends?

Key Questions:

HFC-134a: • A potent GHG

  • Mainly used in mobile air conditioning to replace CFC-12

HCFC-22: • An ODS and potent GHG

  • Mainly used in commercial and residential air conditioning
  • US production and consumption currently declining

Today, regional inverse modeling of HFC-134a and HCFC-22.

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SLIDE 3

Study Period: 2008 – 2012 Network change:

  • Fewer sites in 2008
  • Reduced sampling

frequency in 2012

North American Halocarbon Flask Sampling Network

Model Domain Surface sites

(daily flasks)

Surface sites

(weekly flasks)

Biweekly aircraft profiling sites

x x

Aircraft campaigns Total : ~20000 measurements Data in inversion : ~10000 independent observations Surface and aircraft (< 1 km a.g.l.) data collected at day-time Daily-flask site (WGC) Biweekly aircraft profiling site (CMA) Weekly-flask site (HFM)

enhance

  • ments

KUM BRW

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SLIDE 4

Inversion Method

Observed enhancement Footprint (sensitivity

  • f observed

enhancement to upstream fluxes ) Flux

= x +

Model-data mismatch errors

Solve for: monthly 1o × 1o scaling factors for a prior emission field using a Bayesian inversion

HYSPLIT- NAM12 (2008 – 2012) STILT-WRF (2010)

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SLIDE 5

Synthetic-data inversion

Objective: Design:

“True” emission x Footprints Pseudo observations (pseudo enhancements) Prior emissions

+

Pseudo

  • bservations

Footprints

+

Posterior emissions

To test the credibility of our inversion system to derive national fluxes, given our sampling network A forward calculation: An inverse calculation:

Actual sampling times and locations as real measurements

Posterior emissions = “True” emissions

?

Gaussian Noise

+

Different emission magnitudes and distributions than “true” emission

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SLIDE 6

“Truth” & Priors “Truth” & Priors & Posteriors

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SLIDE 7

20 40 60 80 100 2008 2009 2010 2011 2012 2013

HCFC-22(Gg/y)

20 40 60 80 100 2008 2009 2010 2011 2012 2013

HCFC-22(Gg/y)

20 40 60 80 100 2008 2009 2010 2011 2012 2013 20 40 60 80 100 2008 2009 2010 2011 2012 2013

HFC-134A (Gg/y)

20 40 60 80 100 2008 2009 2010 2011 2012 2013

HFC-134A (Gg/y)

20 40 60 80 100 2008 2009 2010 2011 2012 2013

HFC-134A (Gg/y)

20 40 60 80 100 2008 2009 2010 2011 2012 2013

HFC-134A (Gg/y)

Real-Data Inversion: HFC-134a and HCFC-22 (Multiple Priors)

Prior = EDGARv4.2 Prior = EDGARv4.1 Prior = Population-Based Prior = Population-Based Prior = Saikawa et al (2012)

HFC-134A HCFC-22

Real-Data Inversion: HFC-134a and HCFC-22 (Multiple Priors & Backgrounds)

bkg = 10th prtile,

HYSPLIT-NAM12

bkg = “Curtain” + Air back-trajectory

HYSPLIT-NAM12

* Multiple a-seasonal priors * Inversion results: bkg = 10th prtile,

STILT-WRF

Real-Data Inversion: HFC-134a and HCFC-22 (Multiple Priors & Backgrounds & Transports)

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SLIDE 8

Evaluating derived fluxes

HFC-134a

Independent Data

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SLIDE 9

20 40 60 80 100 2000 2002 2004 2006 2008 2010 2012 HCFC-22 (Gg/y) 20 40 60 80 100 2000 2002 2004 2006 2008 2010 2012 HCFC-22 (Gg/y)

400 450 500 550 600 650 700

20 40 60 80 100 2000 2002 2004 2006 2008 2010 2012 HCFC-22 (Gg/y) 20 40 60 80 100 2000 2002 2004 2006 2008 2010 2012 HFC-134A (Gg/y) 20 40 60 80 100 2000 2002 2004 2006 2008 2010 2012 HFC-134A (Gg/y)

400 450 500 550 600 650 700

20 40 60 80 100 2000 2002 2004 2006 2008 2010 2012 HFC-134A (Gg/y)

Comparison with other national estimates

“Bottom-up”:

U.S. EPA ( ) EDGARv4.2 ( )

“Top-down”: This study ( )

Millet 2009 ( ) Stohl 2009 ( x ) Saikawa 2012 ( ) Miller 2012 ( ) Montzka 2013 ( )

HFC-134a HCFC-22

Barletta 2011 ( ) Transportation (Tg C yr-1) Residential and Commercial (Tg C yr-1) Fossil Fuel CO2 Emission (US EIA)

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SLIDE 10

Conclusions

  • Synthetic-data inversion: Given our sampling network, derived fluxes

using our inversion system are fairly insensitive to priors on a national scale.

  • Real-data inversion:
  • Derived national emissions of HFC-134a and HCFC-22 are fairly

insensitive to priors, backgrounds and transports (within 1sd = ±20%).

  • Seasonally varying emissions: winter emissions are 20 – 50 % lower

than summer emissions for both gases.

  • Comparing to US EPA national emission estimates:
  • HFC-134a: comparable.
  • HCFC-22: ~10 – 50% lower; a relatively more rapid decline.
  • Future work: apply to other gases (e.g. other HFCs, HCFCs, N2O, CH4)
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SLIDE 11

Evaluating derived fluxes

AMT AMT

HFC-134a

Prior (RMSE = 11.8) Posterior (RMSE = 3.5)

Simulation (post)

1:1 line Best Fit 1:1 line Best Fit

Simulation (prior) Simulation (post)