Effects of Tropical Deforestation on Tropospheric Chemistry:A 10-year Study using GEOS-Chem

Prasad Kasibhatla, Duke University

James Randerson and Yang Chen, University of California Irvine

Guido van der Werf, Vrije University

Louis Giglio, Science Systems and Applications, Inc.

Jim Collatz, NASA Goddard Space Flight Center

Ruth DeFries, Columbia University

Doug Morton, University of Maryland

4th GEOS-Chem Users’ MeetingApril 9, 2009

Figure 7.3

Global C Budget for 1990s

Source: IPCC AR4 WG1 Report

black – steady-state preindustrialred – anthropogenic perturbation

+3.2 Gt C/yr

• LUC 0.5-2.7 Gt C/yr (large uncertainty) - primarily tropical deforestation model vs satellite measurements of CO in regions of intense deforestation model simulations with and without fire emissions in deforestation regions

Model Simulations

Model GEOS-CHEM v8-01-02 driven by GEOS-4 4x5 met fields

Emissions

• Fossil fuel combustion: EDGAR with regional inventories for North America (NEI), Europe (EMEP), Asia (Streets), and Mexico(BRAVO) - representative of year ~2000

• Biofuel combustion: Yevich and Logan

• Biogenic VOCs: MEGAN

• Biomass burning: Annually-varying, monthly GFED2 emissions

Runs

• Run 1: 1997-2007 full chemistry simulation (2005 met fields for 2007)• Run 2: 1997-2007 tagged CO simulation using monthly-mean OH fields from Run 1• Run 3: 1997-2007 full chemistry simulation without biomass burning emissions in grid cells with detected humid tropical forest deforestation between 2000-2005 (Hansen et al., PNAS, 2008)

BONA

TENA

EQAS

BOAS-eastEURO

SHSA

NHSA

CEAM

MIDENHAF SHAF

SEAS

CEAS

AUST

Tagged CO Biomass Burning Regions

BOAS-west

• For this talk, focus on SHSA Total fire emissions = 314 Tg C/yr; deforest. fire emissions = 209 Tg C/yr EQAS Total fire emissions = 255 Tg C/yr; deforest. fire emissions = 255 Tg C/yr(Global fire emissions = 2415 Tg C/yr; deforest. fire emissions = 813 Tg C/yr)

MOPITTModel TotalIn-region firesOut-of-region firesFossil fuel/biofuelMethane oxidationBiogenic HC oxidation

700 mb CO

CO

(p

pb)

year

Model vs MOPITT Regional Average CO over EQAS

• Large interannual variability – generally well simulated by model

Model vs MOPITT Regional Average CO over SHSA

MOPITTModel TotalIn-region firesOut-of-region firesFossil fuel/biofuelMethane oxidationBiogenic HC oxidation

CO

(p

pb)

700 mb CO

year

• Seasonal fire season peak reasonably well simulated, but but modeled interannual variability is higher than observed

• Significant overestimate in non-fire season suggesting biogenic hydrocarbon oxidation source of CO is too high

700 mb CO (ppb): Model vs MOPITTJU

LA

UG

SE

PO

CT

MOPITT Model Model - MOPITT

2005

September Surface O3 (ppb): With – Without Deforestation

SEP 1997

SEP 2000

SEP 2005

SEP 2006

September Surface PM2.5 (µg m-3): With – Without Deforestation

SEP 1997

SEP 2000

SEP 2005

SEP 2006

Annual N Deposition: With/Without Deforestation

1997

2000

2005

2006

October 1997 OH % Change: 100*(With – Without Def.)/(With Def) Surface 500 mb

300 mb 700 mb

• Variability of regional average modeled CO in general agreement with

MOPITT CO over EQAS and SHSA lends confidence to GFED2 C

emissions from tropical deforestation since these are major deforestation

regions, BUT interannual variations over SHSA seems to be overestimated.

and MORE IMPORTANTLY, poor simulations of spatial patterns over SHSA.

GFED2 2000-2005 pan-tropical deforestation fire C emissions ~0.8 P C yr-1

best estimate of committed C flux ~ 0.8-1.3 Pg C yr-1

• Significant effect of tropical deforestation on local/regional air quality

parameters next steps will involve analysis of human health/ecological

effects (Miriam Marlier), in concert with next generation of GFED product

and regional atmospheric chemistry modeling over SHSA and EQAS.

Summary

NASA (funding) Bob Yantosca, Philippe Le Sager, Claire Carouge (model)

Louisa Emmons, Merritt Deeter, and MOPITT team (MOPITT data)

Jennifer Logan (discussions)

Jesse Kenyon (programmer)

Acknowledgements