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