POTENTIAL OF GEOSPATIAL TECHNOLOGIES IN LINKING AIRBORNE MEASUREMENTS OF CO2 WIH TERRESTRIAL ...
Description:
Terrestrial
ecosystems are major sources and sinks of carbon. Quantifying their role in the
continental carbon budget requires an understanding of both fast (hours to
days) and longer-term fluxes (years to decades). The Intercontinental Chemical
Transport Experiment-North America (INTEX-NA) is a major NASA science campaign
designed to understand the transport and transformation of gases and aerosols
on transcontinental and intercontinental scales and their impact on air quality
and climate. During the INTEX-NA summer 2004 phase, regional-scale in-situ
measurements of atmospheric CO2 were made from the NASA DC-8 over
the conterminous U.S.
affording the opportunity to explore how land surface heterogeneity relates to
the airborne observations utilizing remote-sensing data products and GIS-based
methods. In this presentation, several derived products from the LANDSAT, NOAA
AVHRR, and MODIS sensors are invoked to specify spatiotemporal patterns of land
use cover and vegetation characteristics for linking the aircraft-based CO2
data with terrestrial sources of carbon. In examining the landscape mosaic
utilizing these available tools, preliminary results suggest that the lowest CO2
mixing ratios observed during the mission were over agricultural fields in IL
dominated by corn then secondarily soybean crops. Low CO2
concentrations are attributable to sampling during the peak growing season over
such C4 plants as corn having a higher photosynthetic rate via the
C4-dicarboxylic acid pathway of carbon fixation compared to C3 plants such as
soybeans. In addition to LANDSAT derived biophysical products, results from
comparisons of the CO2 observations with NDVI values derived from
MODIS data will be presented.
Author's Names: Y. Choi, V.K. Prasad, and S.A. Vay
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ESTIMATING LANDSCAPE-LEVEL CARBON FLUXES FROM TOWER CO2 MIXING RATIO DATA
Description:
Variations
of the CO2 mixing ratio in the atmosphere near the surface result
from several processes, including photosynthesis and respiration of the
underlying ecosystems, vertical mixing near the surface and in the planetary
boundary layer (PBL), and entrainment of air above the PBL. We developed a
novel approach for isolating ecosystem metabolism signals at the landscape
scale (102-104 km2) in an hourly CO2
record using a vertical diffusion scheme coupled with an ecosystem model.
Author's Names: J.M. Chen, B. Chen, K. Higuchi, D. Chan, et al
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MODELING NET ECOSYSTEM PRODUCTIVITY: SCALE ISSUES AND REGIONAL APPLICATION TO THE IBERIAN PENINSULA
Description:
Our research goal is to assess the regional vegetation
dynamics in the Iberian Peninsula (IP). For this purpose, estimations of net
ecosystem production (NEP) from a
productivity ecosystem model, the Carnegie Ames Stanford Approach (CASA) model [Potter
et al., 1993], were compared with
local CO2 flux measurements. The CASA
calibration process aimed the tuning of efficiency scalars directly related to
net primary productivity and soil respiration calculations: maximum light use
efficiency (ε*) and temperature
effect on soil fluxes (Q10),
respectively. Local weather station data was used for climatic inputs, as well
as remotely sensed leaf area index (LAI) and fraction of photosynthetically
active radiation (FPAR) from the MODIS TERRA sensor. Firstly, NEP calculations were performed at different temporal
resolutions, ranging from monthly to daily time steps, in order to assess the
impact of temporal scales on productivity estimates. Both the calibration and
validation procedures showed significant confidence, although the main
processes behind vegetation carbon fluxes were best simulated at temporal scales
ranging from 8 days to monthly. The impact of spatial scale was also analyzed
on the NEP estimates. It was found
that results accuracy was influenced by the data spatial resolution, and,
furthermore, by the tree cover percentage of the aggregated cells. A correction
method was implemented and a reduction of the spatial aggregation error up to
10% was obtained. The long term NEP
analysis for the IP indicates statistically significant positive trends mainly
related to solar radiation positive trends. A less significant negative trend
was also found with a strong spatial autocorrelation behavior.
Author's Names: N. Carvalhais, J. Seixas and R. Myneni
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ALLOCATION AND RESIDENCE TIME OF CURRENT PHOTOSYNTHETIC PRODUCTS IN A BOREAL FOREST USING ...
Description:
We tested the utility of a low-level radiocarbon
(14C) pulse-chase label for quantifying carbon allocation patterns
and the contributions of different components to total ecosystem respiration at
ambient CO2 concentrations in a black spruce forest stand in central
Manitoba, Canada. Approximately .01 moles of CO2
that was isotopically enriched in 14C to ~100,000 times background
atmospheric 14C levels was introduced into the headspace of a 37,000
L translucent dome enclosure. Over a one
hour period, ~70% of this label was photosynthetically assimilated by the
enclosed vegetation. The label application produced a 14C signature
well below regulated health standards, and was easily detectable with
Accelerator Mass Spectrometry (AMS). We followed the allocation and timing of
labeled photosynthetic products by measuring the amount and 14C
content of CO2 respired from different ecosystem components over the
following 30 days.
Author's Names: M.S. Carbone, C.I. Czimczik, K.E. McDuffee, S.E. Trumbore
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Added on: 27-Jul-2005 Downloads: 47
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SPATIALLY DISTRIBUTED CO2, SENSIBLE, AND LATENT HEAT FLUXES OVER THE SOUTHERN GREAT PLAINS
Description: Vegetation
strongly influences the spatial distribution of sensible and latent heat
fluxes, and also controls ecosystem-atmosphere CO2 exchange. We
describe here a methodology to estimate surface energy fluxes and Net Ecosystem
Exchange (NEE) of CO2 continuously over the Southern Great Plains,
using (1) data from the U.S. Department of Energy Atmospheric Radiation
Measurement (ARM) program in
Oklahoma and Kansas; (2) meteorological forcing data from Mesonet facilities;
(3) U.S. Geological Survey (USGS) soil database; (4) MODIS NDVI at 250 meters
resolution; and (5) a tested carbon and isotope land-surface model (ISOLSM,
based on LSM1.0 [Bonan 1996]). The
need for distributed ecosystem modeling was demonstrated by the large spatial
variability in CO2 fluxes across the region, which is typically
modeled as homogeneous cropland. This work addresses U.S. national goals of
estimating regional CO2 sources and sinks, and
provides inputs to forward and inverse models.
Author's Names: S.C. Biraud, W.J. Riley, M.L. Fischer, M.S. Torn, J.A. Berry
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DOWN AND DIRTY: USING A CONTINENTAL, NOT-SO-TALL TOWER TO STUDY TRENDS...
Description: Precise CO2 concentration
measurements at marine stations and tall towers are crucial for quantifying
global trends in atmospheric CO2 concentrations.
We propose that measurements in the continental planetary boundary layer—the
poor cousin of the clean background stations—can be used to understand trends
in, and controls, of atmospheric CO2 concentrations
at local and regional scales as well as global scales. The key is choosing
appropriate time scales of integration for the data. In the US Southern Great
Plains, we are measuring precise CO2 concentrations
continuously at 2–60 m and weekly at 300 and 3300 m above ground level (agl). CO2 flux is measured in individual crop fields and pastures (4 m
towers) and at 60 m. The precise CO2 concentrations
show strong continental influence in both diurnal and seasonal cycles. In
continental regions, atmospheric CO2 profiles are
strongly influenced by atmospheric dynamics as well as ecosystem and
anthropogenic fluxes. Relating site level measurements or atmospheric profiles
to regional CO2 budgets requires methods to represent or evaluate these
influences. We observe inter-annual differences in the
climatology of diurnal cycles (seasonal average diurnal cycles). Using the several years’ data for
boundary layer concentrations, the annual trend in CO2
growth nearly matches the value estimated by National Oceanic and
Atmospheric Administration (NOAA) Climate Monitoring Diagnostic
Laboratory for our latitude band.
Author's Names: M.S. Torn, M.L. Fischer, S.C. Biraud, W.J. Riley, et al
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CONTINUOUS IN SITU MEASUREMENTS OF ATMOSPHERIC O2 AND CO2
Description: Simultaneous
and continuous measurements of O2 and CO2 made in
the air around terrestrial ecosystems have the potential to improve our
understanding of the biogeochemistry of the ecosystem, and may reduce
uncertainties in estimates of terrestrial carbon uptake derived from
atmospheric O2 measurements. Following the
design of Stephens et al. [2001], we
have constructed an instrument that performs continuous in situ measurements of atmospheric O2 and CO2
concentrations. We present design and performance data, along with preliminary
results from a deployment at the Environmental Measurement Site at Harvard Forest
in central Massachusetts.
Author's Names: M.O. Battle, R. Perry, E. Sofen, J. Carpenter, B.B. Stephens
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EFFECT OF RESPIRATION AND CANOPY PARAMETERIZATIONS ON MODELED CARBON FLUX
Description: Simulations
of the global carbon cycle are strongly dependent upon model representations of
the exchange of carbon, energy, moisture and momentum between the atmosphere
and terrestrial biosphere. The carbon flux produced by these biophysical models
is subsequently dependent on the method used to produce respiration and
photosynthesis within the model on both spatial and temporal scales. We use an
updated version of the Simple Biosphere Model (SiB3) to simulate global carbon
flux between atmosphere and land surface, and compare model results to flux
tower and flask network observations. SiB3 assumes no annual net source or sink
of carbon in each gridcell, but the spatial pattern and seasonality of carbon
flux and atmospheric concentration can be strongly influenced by
parameterization of heterotrophic and autotrophic respiration and the
representation of vegetation phenology.
Author's Names: I.T. Baker, K.M. Schaefer and A.W. Philpott
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THE CANADIAN TERRESTRIAL ECOSYSTEM MODEL (CTEM) – THE TERRESTRIAL CARBON CYCLE COMPONENT OF THE ..
Description: The
Canadian Centre for Climate Modelling and Analysis (CCCma) is currently working
towards development of a coupled carbon climate model in which the time-evolving
atmospheric concentrations of greenhouse gases, and in particular CO2,
are computed prognostically on the basis of scenario-specific emissions. The
Canadian Model for Ocean Carbon (CMOC) and the Canadian Terrestrial Ecosystem
Model (CTEM) are the oceanic and terrestrial carbon cycle models implemented in
this coupled framework. This presentation will focus on the terrestrial carbon
cycle component CTEM that is able to grow vegetation from bare ground and
includes processes of photosynthesis, autotrophic and heterotrophic
respiration, phenology, allocation, mortality, land use change, fire, and
competition between plant functional types (PFTs). In the coupled model CTEM
provides a dynamic land surface interface to the climate model by simulating time-varying
vegetation structural attributes as a function of model climate and provides net
fluxes of CO2 between the land surface and the atmosphere. This
presentation provides an overview of how the primary terrestrial ecosystem
processes are modeled in CTEM. It also discusses in some detail the parameterizations
of fire and competition among plant functional types (PFTs). These two
processes have not received adequate attention in the current generation of dynamic
global vegetation models. The fire module of CTEM takes into account all three
aspects of the fire triangle: fuel availability, readiness of fuel to burn
depending on weather conditions, and the presence of an ignition source. The
approach also takes into account the anthropogenic effect on natural fire
regimes. Competition between PFTs is modeled on the basis of a modified form of
Lotka-Volterra equations that, unlike existing applications, allows coexisting
PFTs. Model results at selected locations show that CTEM estimates of vegetation
biomass, leaf area index, fire return interval, biomass burning CO2
emissions and fractional coverages of coexisting PFTs compare reasonably well
with observation-based estimates.
Author's Names: Vivek Arora
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APPARENT TRENDS IN PHOTOSYNTHETIC CAPACITY OF MONSOON ASIA FROM 1982 TO 2002
Description: The
rapid economic growth of Monsoon Asia raises concerns about the future of
carbon stored in the terrestrial ecosystems of the region, especially in connection
with climate change [Tian et al.,
2003; Canadell et al., 2002; Oikawa and Ito, 2001; Esser, 1995]. The regional carbon budget
for 1980s suggests that Monsoon Asia as a whole acted as source [Tian et al., 2003], although some parts of
the region acted as sink. Here we provide some evidence from satellite data
that photosynthetic capacity of the region changed in the manner that suggests
similar conclusion. Comparing the period 1982-1992 and the period 1992-2002, we
found that the photosynthetic capacity of the territory generally decreased in
the forest zone and increased in the non-forest zone of the region.
Author's Names: G. A. Alexandrov, T. Oikawa, and Y. Yamagata
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