Scientific Theme: Advanced Modeling and Observing Systems

Scientific Theme: Planetary Metabolism
Scientific Theme: PLANETARY METABOLISM
PM-01: Biosphere-Atmosphere Interactions
CSD07: Biosphere-Atmosphere Exchange
PM-02: Response of Natural Systems to Perturbations
NGDC07: Anthropogenic Remote Sensing
CSD07: Biosphere-Atmosphere Exchange
PM-01: Biosphere-Atmosphere Interactions
GOAL:
Gain an improved understanding of the role that the exchange of gases between the surface and the atmosphere
plays in shaping regional climate and air quality.
MILESTONE CSD07.1:
Determine the impact of the 2004 forest fires in Alaska and western Canada on the atmosphere
over North America.
ACCOMPLISHMENTS FOR CSD07.1:
During aircraft measurements in 2004 over the northeastern United States, large forest fires were burning in Alaska
and western Canada, and the emissions were regularly observed over eastern Canada and the northeastern U.S.
Using measurements of acetonitrile (CH3CN), a unique tracer for forest-fire emissions, CIRES scientists were able
to detect the emissions and compare the observations to the output from the Lagrangian transport model Flexpart. In
general, Flexpart reproduced the observations very well, in particular when the emissions were released in the model
not at the surface but at an altitude of several kilometers, indicating the importance of pyro-convection.
The measurement results were used to estimate the contribution of forest-fire emissions to the carbon monoxide
(CO) observed over the northeastern U.S. Using acetonitrile as a tracer for forest-fire emissions and chloroform as a
tracer for urban emissions, scientists were able to separate the contribution of these sources to CO. Averaged over
the study period, forest-fire CO contributed 30% and urban CO 70% of the enhancements over the continental CO
background: Urban CO dominated in the boundary layer, whereas in the free troposphere the contributions from
urban and forest fire CO were about equal. The observations in the boundary layer were consistent with those made
from the R/V Ronald H. Brown in the Gulf of Maine. The source attribution was compared with the output from the
Flexpart model. In general, there was a good qualitative agreement between urban CO in the measurements and the
model. However, the model over-predicted the observed urban CO, indicating that emissions inventories for this
trace gas may be too high as observed by others. The agreement between measured and modeled forest-fire CO was
also quite good; in this case, the model reproduced the measurements quantitatively, indicating that emissions from
forest fires are accurately represented in the inventories. This study allows us to estimate the total emissions of CO
due to forest fires in Alaska and western Canada as 22 Tg during the measurement period in 2004, in quite good
agreement with a previous study that used satellite data for CO and an inverse-model estimate of the emission
sources.
PM-02: Response of Natural Systems to Perturbations
NGDC07: Anthropogenic Remote Sensing
GOAL:
Provide spatial and temporal depictions of human activities based on satellite detection and mapping of population
centers, fires, gas flares, and heavily lit fishing boats.
MILESTONE NGDC07.1:
Produce the first global ~1 kilometer map of the density of constructed impervious surface areas.
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