Transferring knowledge from local to global scales through integrated observation and modeling of ph

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The NCAR Biogeosciences Initiative
Transferring knowledge from local to global
scales through integrated observation and
modeling of physical and biological
processes Elisabeth Holland (Program Leader),
Gordon Bonan, Alex Guenther, Natalie Mahowald,
David Schimel, Britton Stephens, Jielun Sun,
Peter Thornton

• Projects and Goals
• Earth System Modeling Create and evaluate
  coupled global models of the interactions between
  climate and biogeochemistry.
• Observations - Studies of terrestrial carbon
  cycle, surface heterogeneity, and multi-scale
  gas/aerosol fluxes. Motivated by modeling, data
  assimilation, and assessment efforts.
• Data Assimilation Gain quantitative
  understanding of atmosphere-biosphere exchange by
  merging observations and process-level models in
  a formal framework.
• Integration into Assessments Combine new
  understanding from Modeling, Observations, and
  Data Assimilation to address how human land use
  and land cover change are altering climate, water
  and carbon cycles, and biogeochemistry.
• Detailed descriptions for each project are
  provided below.

Overview Biological processes play key roles in
the dynamics of the Earth system, modulating
global and local carbon, nitrogen, trace-gas,
water, and energy cycles. In turn, ecosystems
and biogeochemical cycles are sensitive to
physical and chemical forcing and the growing
influence of human activities. The interactions
of humans, natural and managed ecosystems, and
the chemical and physical environment are
complex, multidirectional, and nonlinear, and
their study increasingly requires an integrated
multidisciplinary approach. NCARs Biogeosciences
Initiative is a multidisciplinary collaboration
that includes participants from eight NCAR
divisions in an effort that combines intellectual
challenge with practical significance in the
areas of climate, air quality, ecosystem health,
and water resources. The goal is to build our
understanding of the bio-atmospheric
biogeochemical cycles on the framework of
understanding of water and energy cycles. Those
planetary cycles are strongly influenced by human
activities including agriculture, urbanization,
wildfires, land use and vegetation change.

• Core Science Questions
• How does biogeochemical coupling of carbon,
  nitrogen, iron, and sulfur cycles affect climate,
  air quality, radiative forcing, and ecosystem
  function on regional to global scales?
• How does heterogeneity in terrestrial landscapes
  interact with physical processes in the
  atmosphere to influence ecosystem processes,
  land-atmosphere exchange, and local climate?
• How will human impacts and biogeochemical cycles
  evolve under a future climate, and what are the
  feedbacks and interactions among global and
  climate change, land management, urbanization,
  technological development, economics, and
  decision-making?

Approach Addressing these questions requires the
development of novel approaches to
multidisciplinary research as well as a new set
of tools, including sensors, platforms, data
analysis techniques, and models. The BGS
initiative takes advantage of the breadth of
science undertaken at NCAR to build an integrated
science program that crosses spatial scales from
process to global studies, incorporating both
models and measurements to address the
interactions among biogeochemical cycles. The
Biogeosciences Initiative is aggressively
pursuing scientific and methodological research
on four projects each of which addresses the
three core science questions from a different
perspective.
Assessment
Modeling
Observations
Data Assimilation
Toward global simulation of fully-coupled
climate-carbon-biogeochemistry dynamics
Carbon Cycle The goal of the carbon cycle
sub-project is to quantify exchanges of carbon on
the regional scales most relevant to variability
in ecosystems and climate forcing, thereby
providing critical information needed to predict
the future behavior of oceanic and terrestrial
sources and sinks for CO2 and their climate
feedbacks. This will be accomplished by
developing and deploying advanced tools that will
be proposed as NCAR/ATD facilities that can be
requested by the university community high
resolution instruments to measure CO2, CO, and
H2O concentrations and fluxes, and O2/N2 and
13C/12C ratios from airborne platforms a robust
inexpensive CO2 measurement system suitable for
deployment on communication towers, the ISFF
array, tethersondes, and a calibration facility
to support NCAR-wide carbon cycle measurements.
The goals of the Earth System Modeling project
are to develop a state-of-the-art global coupled
climate-biogeochemistry model, and to use this
model and its components to address each of the
three science questions presented above. We are
studying the effects of coupling on global
climate and biogeochemistry by incorporating the
terrestrial, marine and atmospheric carbon and
nitrogen cycles, aerosols, and atmospheric
chemistry into the existing NCAR Community
Climate System Model (CCSM) framework. The
atmospheric chemistry component includes reactive
species of carbon and nitrogen, providing a
critical link in the nitrogen cycle between the
atmosphere, land surface, and oceans. The
aerosol component includes mineral aerosols,
thought to modulate the open-ocean carbon cycle
by providing iron to surface waters, and fixed-
The industrial age and growing human population
have produced large changes in land surface
characteristics. Throughout the tropics and
extratropics, there have been large decreases in
natural vegetation, which has been converted to
cities or to agriculture. This project uses the
Community Land Model (CLM2) and the Community
Atmospheric Model (CAM2), the land and atmosphere
components of the Community Climate System Model
(CCSM2), to study natural and human-mediated
changes in land cover and ecosystem functions and
their effects on climate, water resources, and
biogeochemistry. Specifically, this work examines
the global climate forcing associated with
croplands, soil degradation, and urbanization and
assesses (a) how changes in land use and land
cover have altered present-day climate and are
likely to alter future climates and (b) the
importance of the land use and land cover change
forcing relative to other IPCC SRES forcings.
nitrogen aerosol species (e.g. nitrates and
ammonium) that link human activities to ecosystem
nitrogen cycles. We are studying the influence
of terrestrial heterogeneity on the coupled
climate-biogeochemistry system with a new land
model for the CCSM that is specifically designed
to capture sub-grid processes such as disturbance
dynamics and age-class distributions, which are
crucial to the accurate estimation of
land-atmosphere exchanges of carbon, nitrogen,
water, and energy. An important goal of the
modeling project is to provide tools that are
directly relevant to the study of human impacts
on the global climate and biogeochemical cycles.
The dominant components of radiative forcing of
climate and their relative magnitudes and levels
of scientific understanding are shown at right.
It is clear from this analysis that
biogeochemical processes have important climatic
consequences, and that carbon and nitrogen
cycles, and aerosols, are of particular
importance. Below, we describe some
aspects of our ongoing research into the global
nitrogen, carbon and mineral aerosol cycles and
the coupling of those cycles to each other and to
climate. We also highlight aspects of this
research which depend strongly on close
collaboration with other components of the NCAR
Biogeosciences Initiative.
NCAR C130 BGS Capabilities
Croplands and Deforestation
Tropical deforestation is thought to create a
warmer, drier climate. In contrast, temperate
croplands such as in the United States cool
surface air temperature by a few degrees compared
to natural forest or grassland. This is primarily
due to the higher albedo of crops compared to
trees and grasses.
Surface Heterogeneity The goals of the surface
heterogeneity sub-project are to quantify
horizontal and vertical transport of trace gases
over heterogeneous surfaces, identify the
heterogeneous surface characteristics responsible
for horizontal transport of CO2, and incorporate
their effects in mesoscale and global scale
models. The scientific objectives will be
achieved by conducting field experiments to
investigate relationships between transport of
CO2 and surface heterogeneity characteristics,
using advanced micrometeorological instruments
and the autonomous CO2 system developed under the
carbon cycle sub-project. We will analyze the
resulting data and apply them to improving
land-surface parameterizations for the BGS Earth
System Modeling and Data Assimilation projects.
Investigation of Effects of Horizontal Transport
of Carbon Dioxide in Long-term Carbon Observations
Tethered balloon vertical profiles up to 1 km
The Carbon Cycle We are using observations across
a range of spatial scales, from leaf to globe, to
evaluate and improve our coupled model and its
components. Some examples for the land model are
shown below.
The Nitrogen Cycle The nitrogen cycle regulates
primary productivity, soil fertility and
agricultural productivity together with water and
other nutrients. Over the last century, human
interactions with these key planetary
biogeochemical cycles have changed through fossil
fuel combustion, use of N fertilizer, agriculture
intensification, and land management. Feedbacks
operating through atmospheric chemistry are key
determinants of the terrestrial N cycle.
Above canopy eddy fluxes at 2 sites
(Percent Cover)
(Percent Cover)
Leaf scale The photosynthesis sub-model is
evaluated against gas exchange measurements
across a range of vegetation types and leaf
environmental conditions. Global model
parameterizations are derived from synthesis of
many such comparisons. Direct connections
between C, N, and water cycles can be studied at
this scale.
The nitrogen cycle is intimately tied to
atmospheric chemistry, and the enhanced emissions
of reactive N are leading to alterations of
atmospheric composition both regionally and
globally (Figure 1). Atmospheric NOx
concentrations regulate the chemical reactivity
of the troposphere, the oxidizing capacity, by
regulating the concentrations of O3 (ozone) and
OH (hydroxyl radical). In turn, the oxidizing
capacity and the biota regulate the lifetimes and
abundance of important radiatively active trace
gases CH4 (methane), CO2 (carbon dioxide), O3,
and N2O. Ozone production, tropospheric oxidizing
capacity and the biosphere are limited by the
availability of reactive nitrogen. The
bio-atmospheric N Cycle is described in Figure 2,
and is driven by the balance between N2 fixation,
N gaseous emissions, and deposition. Wet and
dry nitrogen deposition fluxes are a point of key
interaction with the carbon cycle. The spatial
pattern and magnitude of wet deposition is
strongly influenced by patterns of precipitation
interacting with emissions and chemical
processing. Dry deposition of nitrogen is the
removal of N containing gases by deposition onto
a surface, e.g. leaves, soil, and open water. A
detailed comprehensive study quantifying all of
the different N compounds found in wet and dry
deposition of N over a single site, marine or
terrestrial, has not been done, but some
measurements are available on a spatially
extensive network and can be combined with models
to formulate the spatially explicit patterns
shown here (Figure 3) which can be used for model
evaluation and model input.
To understand the significance of the horizontal
transport of CO2 in nocturnal CO2 balance and
correlations between CO2 transport and surface
heteorogeneity, a pilot experiment was conducted
at the Niwot Ridge AmeriFlux site during
September, 2002. CO2 and wind profiles within the
canopy layer were measured at 8 and 6 locations
within 300 x 400 m2, respectively.
Soil Degradation
HYDRA for multiple vertical and horizontal
sampling
Agricultural practices can degrade soil through
increased compaction and erosion. Soil
degradation reduces soil water holding capacity,
decreases infiltration, and increases runoff.
These changes in the hydrologic cycle alter
surface energy fluxes (net radiation, sensible
heat, latent heat) and thereby alter surface
climate.
Thornton and Law, in prep.
The goals of C-DAS are to prototype assimilation
techniques for estimating carbon sources and
sinks, to evaluate the interaction between the
characteristics of the observing system and the
analysis system, leading to improvements in both,
and to educate students and researchers on
innovative techniques in observations and
analysis. The elements of the C-DAS system are
illustrated on this poster. They include 1) a
reference global atmosphere, 2) a data system
that allows users to extract a subset of the
Reference Global Atmosphere for analysis., 3) A
data assimilation model was developed to estimate
the surface sources and sinks.
Plot and Landscape Scales Coupled model C, N,
water, and energy dynamics are compared to eddy
covariance measurements and to intensive
biometric observations to assess whole-system
behavior at spatial scales of one to several
square kilometers. Previous work at this scale
has demonstrated the importance of disturbance
history in controlling the terrestrial carbon
cycle (at right).These evaluations are carried
out in close collaboration with the Observations
sub-project.
Figure 1.
From Thornton et al., 2002
Multi-scale gas/aerosol flux The goal of the
multi-scale gas/aerosol flux sub-project is to
develop and apply multi-scale flux measurement
methods. These observations will be used to
parameterize and evaluate the BGS Earth System
Model and as inputs for the BGS Data
Assimilation. This includes process-level
enclosure measurements, tower based measurements
of whole canopy fluxes, and regional flux
measurements using airborne platforms. Systems
for measuring vertical turbulent fluxes of gases
and particles will be developed and the
technology transferred to the scientific
community. We will initiate an international
network of reactive gas and aerosol tower flux
measurement sites and support early career U.S.
professors to establish new sites. In addition,
we will conduct field campaigns to address
questions related to biosphere-atmosphere
chemical exchange and transformations.
Aircraft and tower-based eddy covariance and eddy
accumulation capabilities. Available O3,
isoprene, acetone, methanol, acetaldehyde, other
VOC Under development CO, NO/NOy, NH3, aerosols,
CO2
Continental Scale We are using high-resolution
land model simulations (1 km results shown at
right) to quantify the likely influence of
sub-grid distributions of climate and vegetation
type. Remote sensing observations are used to
evaluate the spatial and temporal dynamics of the
high-resolution simulations.
Tethered Atmospheric Chemistry Observing System
(TACOS) capabilities CO2, H2O, O3, VOC, aerosols
Nighttime Lights of the World
Figure 2.
Urbanization
Wet deposition of NH4
Wet deposition of NO3-
The contrast between impervious urban surfaces
and rural vegetated land cover greatly affects
climate and water resources. Urbanization warms
temperature, alters surface energy fluxes
(generally decreasing latent heat flux and
increasing sensible heat flux), decreases
infiltration, and increases runoff.
Biome-BGC results, Thornton, in prep.
Global Scale Remote sensing observations are also
useful for model evaluation at the global scale.
For fully coupled atmosphere-land-ocean
simulations, we will compare predicted
concentrations of atmospheric CO2 to observations
from global surface measurement networks, in
close collaboration with the Data Assimilation
sub-project.
Dry deposition of particulate NH4
Dry deposition of HNO3 (g)
Dry deposition of particulate NO3-
National Geophysical Data Center
All units kg N ha-1 y-1
Holland, Braswell, Sulzman, Lamarque submitted
Figure 3.
Based on DeFries et al., 2000