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CD-03 Abstract

Periodic, Transient, and Spatially Inhomogeneous Influences on Carbon Exchange in Amazonia

David Roy Fitzjarrald — State University of New York, Albany (US-PI)
Osvaldo Luiz Leal de Moraes — UFSM - Universidade Federal de Santa Maria (SA-PI)

Motivation





We propose observations and analyses to infer transports of CO2, water

vapor, and energy from the natural and the disturbed rain forest by making direct and

inferential flux measurements. A major focus is to determine how Amazonian carbon exchange

is affected by natural and human-induced temporal and spatial variability in the

ecosystem.





Objectives







  1. To describe the radiation environment of the upper and lower canopy in natural and

    logged regions, to understand how the intensity and quality of incoming radiation are

    altered by cloudiness, and to determine what is the resulting effect on net ecosystem

    exchange of C (NEE).


  2. To describe and model the mechanisms of turbulent canopy-atmosphere exchange in regions

    of closed-canopy primary forest, near natural gaps, and in the cut-over mosaic of a

    selectively


  3. Logged site.


  4. To relate canopy layer and boundary layer concentrations of potential temperature, CO2,

    and H2O, and use this information to estimate their partition into surface and

    canopy source components.


  5. To determine what limits the accuracy of long-term tower flux observations of net

    ecosystem exchange (NEE) in the rain forest.






Work Plan -- Detecting the Importance of Inhomogeneities on Observed Carbon Fluxes







  • To describe the ecosystem light environment, we plan to locate radiation booms on the 60

    m Rohn towers at the primary forest (PF) and selective logged (SL) sites. These booms are

    self-contained units that provide long-wave, short-wave, PAR, and net radiation in each

    vertical direction, and include an electronic level readout. A rotating shadowband

    radiometer in a clearing will measure diffuse and direct radiation components.


  • To make estimates of the respiration rate from tower CO2 concentration

    observations, continuous acoustic wind profiler measurements will be maintained. By

    monitoring the backscatter signal, the thickness of the stable boundary layer will be

    obtained and the nocturnal surface flux (respiration rate) found by the layer budget

    approach.


  • To determine the importance of natural and artificial gaps on canopy venting,

    microclimatic studies using turbulence instrumentation and sub-canopy sounding balloons

    will be deployed at several sites during IFCUs. For selected periods, balloons will also

    carry small-diameter tubing that will sample the CO2 profile in the gap, using

    a battery-operated pump connected to a CO2 analyzer.


  • Sub-canopy flux measurements. The measurements, in conjunction with the profiles of T,

    q, and [CO2] proposed by Wofsy and Goulden, offer a unique opportunity to

    measure and then parameterize the mechanisms of mass exchange between the rain forest and

    the lower atmosphere.


  • Tower representativeness. We will apply and refine existing techniques to determine the

    source region for surface-based and canopy fluxes, using a vertical profile of turbulence

    intensity appropriate to the undisturbed and logged forest sites, respectively. We propose

    to operate a sonic anemometer at levels just above the canopy with the objective to

    determine at what times this level and tower top may lie in different turbulent

    microclimates.


  • To track cloud fraction and cloud base as 30 s intervals, a ceilometer will be deployed.


  • To determine cloud type and to make another estimate of cloud fraction, a digital sky

    camera will be operated for selected periods. In analysis we will seek to link these cloud

    characteristics from the surface observations to those from satellite images.


  • Two secondary tower sites, to be fitted with automatic weather stations that communicate

    to the PFsite by radio modem, will provide the minimal surface network for use with

    mesoscale modeling. This will also provide the framework to decide if there are systematic

    biases in climate observations from riverside stations.


  • Daytime mixed layer thickness will be found using established relationships between

    cloud base and mixing layer thickness, using the sounder and ceilometer data in tandem.






Training





We are prepared to give a training course in micrometeorological methods used in

ecological studies, to be held in and around Santarém. Since several of the ASRC team are

fluent in Portuguese, the material in these courses can be presented in that language or

in Spanish. In addition, transfer of the data acquisition system hardware and software to

local teams is planned.





Research Team Responsibilities







State University of New York









  • David Fitzjarrald: Design and deployment of the boundary layer sounding system for the

    respiration estimates; planning the flux measurement training program


  • Kathleen Moore: Primary responsibility for the field investigation of the forest gap

    microenvironment studies


  • John Sicker: Fabrication of mounting systems for tower-based radiation and turbulence

    instrumentation; electronic interfaces with other groups, cabling, in the design and

    maintenance of computer systems


  • Ricardo Sakai: Responsible for coordination of field operations in Brazil, assisting in

    the training program, designing data analysis strategy


  • Otavio Acevedo, Jeffrey Freedman, and Ralf Staebler (Ph.D. students): Upgrade to the

    group's digital sky camera, and the interface between ceilometer and the data acquisition

    system, and archiving data








Universidade Federal de Santa Maria, RS, Brazil









  • Osvaldo Moraes: Analysis of turbulent spectra sub-canopy CO2 transport

    models. He will have joint responsibility for field operations and will provide models of

    turbulent transport within and above the rain forest canopy






Links to Other Groups





Our efforts link to the continuous flux measurements proposed by Wofsy et al. (Harvard

University) at the undisturbed Tapajós site and similar observations proposed by Goulden.

(University of California, Irvine) at the logged site. The canopy-atmosphere exchange and

nocturnal respiration studies link directly to the 222Rn tracer studies proposed by

Martens (University of North Carolina) and to chamber measurements planned by Keller,

Crill, and Silver and by Goulden. (U.S. Forest Service, University of New Hampshire).

Studies of turbulence in the sub-canopy and roughness layers are done in collaboration

with O. Moraes (Federal University of Santa Maria, RS, Brazil) . The proposed work links

directly with the mesoscale model studies of the river breeze planned by M. Silva Dias

(University of São Paulo, Brazil ).





Activities







  • Installation of automatic weather stations, cloud ceilometer, July-December 1998


  • Automatic tower flux measurements; radiation suite on towers, October 1998-2000 (to be

    reinstalled after logging at disturbed forest)


  • IFC gap microclimate measurements, Gap inventory at tower sites, 1-2 months/year

    1998-2000

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