Using Simulated OCO Measurements for Assessing Terrestrial
Carbon Pools in the Southern United States
PI: Nicolas H. Younan
Roger L. King, Surya S. Durbha, Fengxiang Han, Zhiling Long, Jian Chen
Project Goal
This project is focused on the assessment
of terrestrial carbon pools in the south east
and south central United States. In particular,
this investigation intends to:
 Leverage multiple NASA sensors, the
terrestrial ecosystem model (CASA), and a
transport model.
 Undertake a Rapid Prototyping (RPC)
experiment to address the need to quantify
the carbon exchange over different
ecosystems.
 Test how well data from Orbiting Carbon
Observatory (OCO) observations and CO2
measurement networks, models constrain
CO2 fluxes at model-grid resolution.
atmospheric CO2 accumulation and for
mitigating impacts of global warming. Such an
inventory is a prerequisite for regional trading of
CO2 emissions. Results from the team’s DOE
funded work has indicated that the annual
terrestrial carbon sequestration in south east and
south central United States (soil, forest, crop,
CO2 in Atmosphere
Photosysthesis
Decomposition
Decomposition
Decomposition
Biomass in
Plants
Agricultural
products
Residue in
fields
Bioenergy
Waste input
Forestland
29.4 Tg C/yr
54.6%
Cropland
15.1 Tg C/yr
28%
Grassland
9.4Tg C/yr
17.5%
Potential Annual C Sink: 53.9 Tg C/yr
Figure 1: Current annual carbon sequestration in south
east and south central U.S
Societal Impact
Carbon dioxide (CO2) is a greenhouse gas,
whose atmospheric concentration has
increased from 280 to 370 parts per million
since the beginning of the industrial age.
These rapid increases have heightened
concerns about CO2’s role in global climate
change. The analyses of regional carbon
sources and sinks are essential to assess the
economic feasibility of various carbon
sequestration technologies for mitigating
Humification
/Transformation
Soil C
Waste input
Figure 2. Carbon recycling in the future U.S.
bioenergy-focused agricultural
pasture and house/furniture) can offset 40% of
the total annual greenhouse gas emission in this
region (Figure 1). Through proper policies and
best management, about 10.1% of the total
greenhouse gas in the region can be further
offset by terrestrial sequestration.
The study
is also looking at the nutrient fertilizer
requirements for sustainable biomass supply to
meet U.S. bioenergy goal (Figure 2).
This RPC experiment is aligned with the
NASA Earth-Sun System Applied Sciences
Program’s Carbon Management Program
Element (FY 2006) plan that focuses on
evaluation of OCO products through simulations
of observations and baseline impact of OCO
observations on existing decision
Figure 3. RPC experimental design
support tools for carbon sequestration and
emissions.
Methodology
The Orbiting Carbon Observatory (OCO)
[http://oco.jpl.nasa.gov/] mission will make
the first global, space-based measurements
of atmospheric carbon dioxide (CO2) with
the precision, resolution, and coverage
needed to characterize CO2 sources and
sinks on regional scales. This RPC
experiment is focused towards the evaluation
of CO2 column measurements from simulated
OCO data (Observation Systems Simulation
Experiment (OSSE’s)) and relating these to
terrestrial biospheric exchange of carbon from
terrestrial surfaces (Figure 3).
Sensitivity analysis of how much Net
Primary Production (NPP) increase is
required to sustain the regional terrestrial
carbon sink of the study area. Net Ecosystem
Productivity (NEP) defined as Net Primary
Production (NPP) minus the heterotrophic
soil respiration predictions is used to infer
variability in regional scale carbon fluxes and
to better understand patterns over terrestrial
carbon sinks. The CASA model assimilates
satellite NDVI data (e.g. MODIS sensor) to
estimate spatial variability in monthly net
primary
production
(NPP),
biomass
accumulation, and litter fall inputs to soil
carbon pools. The estimates of carbon products
is calibrated with field-based measurements of
crop production, forest ecosystem fluxes, and
inventory estimates of carbon pool sizes at
multiple locations in the southeastern and south
central United States. Comparative predictions
from an atmospheric transport model and
measurements
of
atmospheric
carbon
abundances from OCO and at observation sites
distributed over the regions of interest is also
being conducted. The spatial pattern of the
observed and predicted differences can be used
to infer the spatial distribution of sources and
sinks of carbon dioxide.
Science Questions
This RPC experiment seeks to address the
following questions:
 What information about carbon exchange can
be obtained from OCO high-precision column
measurements of CO2?
 How can we integrate top-down OCO
measurements
with
ground
based
measurements, atmospheric and terrestrial
ecosystem models to quantify carbon exchange
over different ecosystems?
 What are the current annual rates of terrestrial
carbon sequestration in each state of the Southeast and South-central U.S.?