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)
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
- 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).
- 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
- Logged site.
- 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.
- 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
- 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
- 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.
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
- 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 ).
- 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