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Kaitlyn Steele
Bryan Duncan, NASA-GSFC
Juying Warner, UMBC-JCET
Eric Nielsen, NASA-GSFC
Research and Discover 2010
Surface [CH4] in NASA GEOS-5 CCM
Wang et al. 2004
Sources:*Bacterial methanogenesis:
CH3COOH CH4 + CO2
CO2 +4 H2 CH4 +2 H2OThermogenic productionIncomplete combustion
Sinks: Methane oxidation in soil & water:
CH4 + 2 O2 CO2 + 2 H2O
Oxidation by OH radical: OH + CH4 H2O + CH3
Stratospheric reaction with Cl:CH4 + Cl CH3 + HCl
Tropospheric lifetime: τ ~ 8-9 years
* ~80% from methanogenesis
Annual Methane Source Distribution
Longitude
Coal, municipal waste
Swamps, biomass burning, biofuel Rice, animals, biofuel
Dlugokencky 2009. http://www.esrl.noaa.gov/gmd/ccgg
No definitive explanation regarding slowdown in CH4 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
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 CH4, of which 71 used to retrieve CH4
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
Global Monitoring Division Surface Stations
Canada
Hungary
Hawaii
Guam
Antarctica
CH4 energy CH4 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
CH4 biomass burning CH4 rice production
October
GEOS-5 CCM: Seasonal Variability in UT: Wetland Source
Strong wetland source
CH4 from other sources
January April
July October
Seasonal Variability Observed by AIRS ~ 350 mb
Feb
July
(ppbv)
NASA Global Precip. Climatology Project Rainfall
Feb
CH4 “poor” air at surface lofted to UT
July
All methods for monitoring CH4 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 CH4 at surface influenced by location of site
with respect to sources of CH4
Variability in CH4 in UT caused by seasonal variation in sources convolved with seasonal variation in deep convection
Bryan DuncanJuying WarnerEric Nielsen
Yasuko YoshidaXiaohua PanZigang WeiResearch &
Discover
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
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