PNNL-13501 - Pacific Northwest National Laboratory

Enhancing Emissions Pre-Processing Capabilities for Atmospheric Chemistry
Study Control Number: PN00040/1447
Elaine G. Chapman, Jerome D. Fast, W. Richard Barchet
Atmospheric chemical transport models are used in research ranging from global climate change to pollution abatement
strategies for meeting urban air quality standards. Emissions are an essential input to these models. This project
enhanced the efficiency, effectiveness, and accuracy with which model-ready emissions may be generated.
Project Description
The purpose of this project was to enhance our capability
for modeling atmospheric pollutants. Observed pollutant
concentrations result from local emissions reacting with
chemical species transported into an area from long
distances. To accurately model and understand such
situations, we need to capture the local, regional, and
synoptic meteorological and chemical factors, as well as
to provide accurate local-, regional- and continental-scale
emissions inputs. We designed algorithms and developed
computer codes to combine different pollutant emissions
inventories with differing spatial and temporal scales.
The resulting nested emissions provide substantially
improved model input relative to the standard procedure
of using only one inventory. We also expanded the
chemical detail and number of emissions inventories
available for routine use with our models, and generalized
our in-house emissions preprocessing programs. This
project advanced our ability to readily and efficiently
assemble the most appropriate emissions input for a given
model application.
Results and Accomplishments
We successfully realized substantial increases in
efficiency by generalizing, standardizing, and automating
selected in-house emissions processing programs. Staff
prepared emissions inputs for two separate modeling
efforts, one of which involved emissions inputs from a
new global inventory that we had not previously worked
with. Using programs enhanced under this project, one
person was able to generate the necessary model-ready
emissions inputs, with selected graphics and summary
information, in less than 8 hours. We estimate it would
have required 3 days for each modeling effort (6 days
total) prior to the improvements realized under this
project.
The more efficient processing programs were used to
generate a prototype nested emissions data set for
modeling applications. We successfully wrote and tested
216 FY 2000 Laboratory Directed Research and Development Annual Report
computer codes for reading, regridding, speciating, and
nesting emissions inventories with different temporal and
spatial scales. The codes were developed in a generic
format, to permit ready use in future modeling efforts.
We used these programs to generate a prototype doublenested,
model-ready emissions input data set for modeling
air quality in the vicinity of Phoenix, Arizona. The final,
model-ready emissions data set included California Air
Resources Board emissions for southern California and
Arizona Department of Environmental Quality emissions
for Phoenix nested within the continental-scale National
Emissions Trends Inventory of the U.S. EPA, all nested
within global emissions data from the Global Emissions
Inventory Activity. Model predictions capture the major
features, and many minor features, of chemical
measurements taken in Phoenix, and unequivocally show
that ozone concentrations in the Phoenix area are
governed mainly by hydrocarbons, rather than by locally
emitted nitrogen oxide (NOx) compounds. Interpretation
of regional influences on Phoenix urban chemistry was
significantly enhanced through use of the detailed nested
emissions input, emphasizing the importance of emissions
on overall model results.
Summary and Conclusions
Although significant improvements in processing
capabilities were realized and a novel, nested emissions
set successfully generated and used, the major conclusion
of this work is that such advances represent only a
stopgap measure relative to the direction of atmospheric
chemistry modeling. Publicly available, gridded
emissions inventories represent static levels. These
inventories generated assuming average conditions over a
given time period. Such inventories are processed offline
to produce model-ready emission fluxes. We foresee
modeling efforts, particularly regional-scale modeling
programs, moving toward needing dynamically derived
emissions that reflect specific meteorological conditions
in a specific time period in a specific geographic region.
We also foresee a need to eventually couple emissionsgenerating
modules directly with the chemical,