TOP-DOWN CONSTRAINTS ON REGIONAL CARBON FLUXES USING CO2:CO

CORRELATIONS FROM AIRCRAFT DATA

P. Suntharalingam, D. J. Jacob, Q. Li, P. Palmer, J. A. Logan, C. Gerbig, R.

Yantosca

Harvard University

S. A. Vay, G. Sachse

NASA Langley

D. Streets

Argonne National Laboratory

TRACE-P March-April,

2001

COBRA-2000 August 2000

Regional CO2/CO Emissions Ratios March 2001 (from a priori inventories) Observed CO2:CO Correlations

(TRACE-P Flight DC8 #16, March 29, 2001)

CO

2 (m

ol)

CO (mol)

ATMOSPHERIC MEASUREMENTS OF CO2:CO CORRELATIONS CAN PROVIDE UNIQUE INFORMATION ON SOURCE REGION AND

SOURCE TYPE

CHINA

JAPAN

- The emissions ratio varies with combustion efficiency

- Range in regional emissions ratios reflects mix of sources and variation in fossil fuel combustion ratio

Boundary layer, off China (slope = 12)

Ascent out of Japan (slope = 65)

Measurements above 500hPa (slope = 60)

The NASA/GTE TRACE-P Aircraft MissionSampled Asian outflow over the Western Pacific in the spring of 2001 (Feb.

28th – April 10, 2001)

CO2 measurements : S. Vay; CO measurements: G. Sachse

NASA, Langley

GEOS-CHEM CO2 Simulation Boundary Layer, March 10-20, 2001

MOTIVATIONTo identify constraints on CO2 sources using analysis of observed

CO2/CO correlations

Combine analysis of aircraft data with model simulations

to evaluate bottom-up inventories

GEOS-CHEM Model

Bottom-up Inventories

APPROACH

Aircraft Data

Improved CO2 Fluxes

ASIAN EMISSIONS INVENTORIES

FOSSIL FUEL

MODELGEOS-CHEM (global)

2ox2.5o; 48 levels

BIOFUEL

BIOMASS BURNING BIOSPHERE

Heald et al. (2003) Duncan et al. (2003)

Streets et al. (2003)

CASA, Randerson et al.(1997)

Streets et al. (2003)

Consistent combustion inventories for CO2 and

CO

Shown: March, 2001

ASIAN CO2 SOURCESSeasonal Cycle : CO2

TRACE-P

TRACE-P at seasonal CO2 maximum

Biospheric emissions are 65% of Chinese total, according to bottom-up inventories

Average over TRACE-P period

REGIONAL ANALYSIS OF TRACE-P MEASUREMENTS

Offshore ChinaOver Japan

Slope (> 840 mb) = 51

R2 = 0.76

Slope (> 840 mb) = 22

R2 = 0.45• Analysis conducted on a regional basis

• Factor of 2 difference in boundary layer CO2:CO correlations between the two regions

Japan

China

CO2 Simulation Based on A Priori Inventories

• Model overestimate of CO2 in boundary layer

• Discrepancy greatest off China

JAPANALL FLIGHTS

MODEL

GEOS-CHEM CO2 simulation sampled along TRACE-P flight tracks

OBSERVATIONS

CHINA

CO2:CO CorrelationsRegion : Offshore China

Simulation : Bottom-up inventories for CO2 and CO

Modeled BL slope close to bottom-up emissions ratio for China (58)

• Modeled boundary layer CO2:CO slope higher than observations.

• This is due to underestimate of CO and overestimate of CO2 in the boundary layer

CO CO2

MODEL

OBS

CO simulation : Palmer et al. [2003]

TRACE-P Observations GEOS-CHEM Model

Slope = 22

Slope = 57

Which CO2 Emissions Source is too High ?

•Modeled CO2:CO ratios higher than observations

• Modeled boundary layer CO2 is higher than observations

• Reconciliation of modeled CO2 with observed CO2 and CO2:CO ratios requires a reduction in a source with a high CO2:CO emissions ratio

Region : Offshore China

Mean BL slope = 22

MODEL

OBS

Mean BL slope = 57

GEOS-CHEM ModelTRACE-P Observations GEOS-CHEM Model

IMPROVED CO2 and CO SIMULATIONS

•Better match to observed boundary layer concentrations and correlations

•Obtaining CO2 fuel emission changes consistent with CO depends on cause of a priori CO underestimate (activity rate vs. emissions factor error)

CO2 : 45% reduction in Chinese biospheric flux

CO : 54% increase in Chinese fuel emissions (Palmer et al. 2003)

Slope = 18

R2 = 0.52

Slope = 55

R2 = 0.66

Slope = 29

R2 = 0.67

Mean Vertical Profiles in Chinese Outflow Region

COCO2

Observations

A Priori

Best-case

TRACE-P

A Priori

Best-Case

The COBRA-2000 Aircraft MissionTropospheric measurements over North America in August 2000.

CO2 and CO Measurements : C. Gerbig, S. Wofsy, B. Daube, J. Lin, A. Andrews, Harvard University

Measurements sampled summer

CO2 drawdown and intense biomass

burning

SEASONAL CYCLE

CO2

CO

COBRA-2000

CO2/CO Emissions ratio (mol/mol)

CO2:CO Correlations Selected Flights (2-8 km)

CO

2 (

pp

mv)

CO (ppbv)

Positive : mix of combustion and biospheric

respiration

Negative : Biospheric uptake

FLIGHT TRACKS

-400 2000-200

A PRIORI EMISSIONS : North America

CO2 and CO INVENTORIES

Fossil : Marland et al. 2001, Logan et al.

Biomass Burning : Duncan et al. 2003

Biosphere : CASA (Olsen and Randerson. 2003)

FOSSIL

BIOMASS BURN

BIOSPHERE (CASA)

31%12%

57%

37%

63%

CO2 CO

Fossil

Biosphere

Biomass Burning

Fossil (43)

Biomass Burning (12)

Shown : August 2000

TOTAL (-27)

Biosphere

CO

CO2

Regional CO2/CO Flux Ratio

IDAHAO-MONTANA FOREST FIRES (August 2000)

Biomass Burning Plumes from COBRA-2000

Aug 19

Aug 24

Alt

(km

)

-Forest fire emissions had significant impact on tropospheric CO over North America

-Estimated contribution : 9 Tg CO for August, 2000 (Lamarque et al. 2003)

GEOS-CHEM CO Simulation August, 2000; Alt : 2.8 km

MOPITT CO Column shows enhancements downwind of fire

location

COMPARISON OF GEOS-CHEM SIMULATION WITH COBRA-2000 MEASUREMENTS

GEOS-CHEM CO2 and CO simulations sampled along COBRA-2000 flight tracks

CO2 Altitude Profiles : All Flights

- Modeled CO and CO2

overestimate observations

- Diurnal cycle in CO2 fluxes improves model simulation in boundary layer

- To use CO2:CO correlations as constraints on CO2 fluxes, we must first identify source of CO overestimate

CO

All Flights

MODEL

OBS

MODEL without diurnal cycle in

biospheric fluxes

COMPARISON OF GEOSCHEM CO WITH MOPITT COLUMNS

Modeled CO columns higher than MOPITT

especially in and downstream of

high fire regions

GEOS-CHEM CO Simulation

Li et al. [2003]

MOPITT CO Column, August 2000

GEOS-CHEM CO Column, August 2000

CO2:CO CORRELATION ANALYSIS OF BIOMASS BURNING SIGNAL IN COBRA-2000 MEASUREMENTS

- Modeled correlations underestimate observed slope

- Reduction in biomass burning source improves simulation of correlations and absolute concentrations

- A likely source of error in biomass burning inventory is from omission of day to day variability in modeled fire emissions

CO2CO

OBS

REDUCE BIOMASS BURNING

A PRIORI

COBRA-2000 GEOS-CHEM

S = 36

R2 = 0.42

S = 14

R2 = 0.64

S = 25

R2 = 0.64

Analysis in Depicted Region at 2-4 km

SUMMARY

• Observed CO2:CO correlations from aircraft data display distinct slopes reflecting regional and source type signatures, and provide top-down constraints to evaluate regional emissions inventories

• Asian outflow : CO2:CO constraints indicate an overestimate in bottom-up Chinese biospheric CO2 emissions for March 2001.

• North America : Success in constraining CO2 fluxes using CO2:CO constraints requires accurate characterization of fire influences. CO and correlation constraints indicate an overestimate in the biomass burning inventory for August 2000.

• An optimal set of emissions adjustments requires a formal inverse analysis of the coupled CO2:CO system

POSTERS : Top-down Constraints from Multiple-Species Correlations

A52B-0797: P. Palmer et al.

Exploiting observed CO:CO2 correlations in Asian outflow to invert simultaneously for emissions of CO and CO2

A52B-0796 : Y. Xiao et al.

Constraints on Asian and European Sources of Methane from CH4 - C2H6 - CO Correlations in Asian Outflow

ACKNOWLEDGEMENTS

NOAA OGP Global Carbon Cycle Program

NASA Carbon Cycle Program