1. Kaitlyn Steele Bryan Duncan, NASA-GSFC Juying Warner, UMBC-JCET Eric Nielsen, NASA-GSFC Research and Discover 2010 Surface [CH 4 ] in NASA GEOS-5 CCM

2. Methane Sources Wang et al. 2004 Sources: *Bacterial methanogenesis: CH 3 COOH  CH 4 + CO 2 CO 2 +4 H 2  CH 4 +2 H 2 O Thermogenic production Incomplete combustion Sinks: Methane oxidation in soil & water: CH 4 + 2 O 2  CO 2 + 2 H 2 O Oxidation by OH radical: OH + CH 4  H 2 O + CH 3 Stratospheric reaction with Cl: CH 4 + Cl  CH 3 + HCl Tropospheric lifetime: τ ~ 8-9 years * ~80% from methanogenesis

3. Annual Methane Source Distribution Longitude Latitude Coal, municipal waste Swamps, biomass burning, biofuel Rice, animals, biofuel

4. Dlugokencky 2009. http://www.esrl.noaa.gov/gmd/ccgg

5.  No definitive explanation regarding slowdown in CH 4 growth rate  Several hypotheses  Increase in OH  Reduced emissions, especially from Soviet Union  Renewed growth  Decrease in OH influenced by solar cycle  Economic growth of developing countries

6. Methods of Monitoring Methane  In situ  NOAA ESRL Global Monitoring Division (GMD)  Surface level  Japanese Airline Data (JAL)  Troposphere  Satellite  Atmospheric Infrared Sounder (AIRS) on EOS/Aqua  Hyperspectral scan with 200 channels in 7.66 μm absorption band of CH 4, of which 71 used to retrieve CH 4  Most sensitive in middle and upper troposphere (~300 mb) (Xiong et al. 2008)  Modeling  GEOS-5 Chemistry-climate model (CCM) http://aqua.nasa.gov/about/instrument_airs.php

7. Global Monitoring Division Surface Stations

9. GEOS-5 CCM: Source Contributions to Total Methane Canada Hungary Hawaii Guam Antarctica

10. CH 4 energy CH 4 animals July GEOS-5 CCM: Methane in Upper Troposphere (UT): Surface Sources in Relation to Areas of Deep Convection CCM rainfall as a proxy for deep convection

11. CH 4 biomass burning CH 4 rice production October

12. GEOS-5 CCM: Seasonal Variability in UT: Wetland Source Strong wetland source CH 4 from other sources January April July October

13. Seasonal Variability Observed by AIRS ~ 350 mb Feb July (ppbv) NASA Global Precip. Climatology Project Rainfall Feb CH 4 “poor” air at surface lofted to UT July

14. Conclusions  All methods for monitoring CH 4 have strengths and limitations, so we used a suite of observations (i.e., GMD, JAL, AIRS) in conjunction with the GEOS-5 CCM  Can AIRS (UT ~ 300 mb) help us identify variation in methane sources? It is difficult to constrain methane’s sources, particularly from space, because: 1) methane’s long lifetime results in a large background concentration 2) there are many methane sources that are often overlapping in their distribution  Using the GEOS-5 CCM, we found:  Variability in CH 4 at surface influenced by location of site with respect to sources of CH 4  Variability in CH 4 in UT caused by seasonal variation in sources convolved with seasonal variation in deep convection

15. Acknowledgements Bryan Duncan Juying Warner Eric Nielsen Yasuko Yoshida Xiaohua Pan Zigang Wei Research & Discover

16.  Wang, J.S., J.A. Logan, M.B. McElroy, B.N. Duncan, I.A. Megretskaia, and R.M. Yantosca. 2004. A 3-D model analysis of the slowdown and interannual variability in the methane growth rate from 1988 to 1997. Global Biogeochemical Cycles. 18: GB3011, doi:10.1029/2003GB2180  Xiong, X., C. Barnet, E. Maddy, C. Sweeney, X. Liu, L. Zhou, and M. Goldberg. 2008. Characterization and validation of methane products from the Atmospheric Infrared Sounder (AIRS). J. Geophys. Res. 113: G00A01, doi:10.1029/2007JG000500 http://aqua.nasa.gov/science/formation_flying.php