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CD-14 Abstract

CO2 Budget Regional Airborne Study (COBRA)-Brazil

Maria Assunção Faus da Silva Dias — IAG/USP (SA-PI)
Steven Charles Wofsy — Harvard University (US-PI)

Motivation. The Amazon Basin is a key component of the

global carbon

cycle, containing one-half of the world's undisturbed tropical forest

and accounting for ~10% of global terrestrial net primary

productivity.  Current estimates of carbon fluxes in Amazonia at the

regional and Basin scales are subject to large uncertainties that

propagate into the global carbon budget.  Regional and Basin scale

carbon exchanges fall into the "missing scale" in carbon cycle


due to a) dearth of CO2 observations over the continent to constrain

inverse models and b) lack of independently validated methodologies to

scale up local measurements. 

The proposed study will conduct in-situ airborne


of CO2 and CO in the lower- and mid-troposphere over the Amazon Basin.

The proposed strategy for observations and analysis will provide

direct estimates of carbon fluxes at the missing regional and Basin

scales.  We plan to conduct this study during both wet and dry seasons

to capture the seasonal variability and to complement LBA airborne

remote-sensing missions. 


directly quantify regional and Basin-scale fluxes in

Amaztnia using

airborne measurements of CO2 and other tracers in and above the

planetary boundary layer (PBL);

  • establish the relationships

    between vertical concentration

    gradients and exchange fluxes observed at the eddy flux towers in LBA

    and over adjacent regions;

  • test hypotheses

    central to LBA that Amazonia is a major net

    source or sink for CO2;

  • characterize

    horizontal and vertical distributions of

    atmospheric CO2 over Amazonia for the purposes of planning remote

    sensing instrumentation


The proposed strategy has been successfully implemented

in a

pilot study (COBRA 2000) conducted over North America and consists of

the following complementary approaches:

  • Lagrangian regional experiments: diurnal airborne

    measurements of

    CO2, CO, and H2O within and above the PBL in an airmass-following

    framework which yields regional fluxes and their variations across

    different disturbance regimes. 

  • Eulerian experiments: vertical profiles at different

    times of the day

    over selected locations yield first-order estimates of carbon fluxes

    and define the diurnal variations for each region  

  • Large-scale surveys: sampling of large-scale CO2

    distribution along

    the synoptic flow pattern, combined with knowledge of diurnal

    variations from the Eulerian experiments, gives Basin-scale fluxes

  • Hemispheric-scale cross-sections: observations during

    transit flights

    between North Dakota and Brazil will enable construction of CO2

    cross-sections that span from the mid- to tropical latitudes


Direct estimates of CO2 fluxes at regional and Basin

scales to test

ideas about net sources or sinks of CO2 in Amazonia, and against which

methods for scaling up local measurements can be evaluated, including:

  • Regional scale (~200-300km) CO2 fluxes in disturbed and


    regions of Amazonia

  • Basin scale flux estimates derived from large-scale

    horizontal and

    vertical gradients

Vertical and horizontal distributions of CO2 in the

troposphere over

Amazonia and between the American Midwest and Brazil that:

  • improve estimates from inverse studies by filling an



  • constrain CO2 fields generated by coupled

    atmosphere-biosphere models

  • assist in the development of space-borne sensors for


    atmospheric CO2

  • evaluation of a simpler method to quantify carbon

    fluxes, using

    routine atmospheric profiling over the same location, which can be

    more widely adopted.

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