Investigating the Roles of Aerosols, Stratospheric Transport, and Natural and Anthropogenic Emissions on Tropospheric Ozone Using a Tropospheric/Stratospheric Model

Research Objective

We are developing a global, three-dimensional atmospheric model, IMPACT, which contains both a prognostic stratosphere and troposphere. IMPACT is driven by meteorology from either a general circulation model or data-assimilated fields. We will use IMPACT to assess impacts of energy-related emissions in the lower and free troposphere, as well as near the tropopause.

Computational Approach

IMPACT can be run on a variety of platforms, including the Cray C90, J90, T3D, T3E, IBM SP2, and others. Simulations are computationally expensive, due to the large number of chemical reactions involved and stiffness of the equation set. IMPACT has been developed for use on massively parallel computers. It makes use of domain decomposition, high-level communications, variable 3D resolution, and the master-slaves concept.

Accomplishments

IMPACT has been used to simulate the ²²²Rn and ²¹⁰Pb cycles, which are tracers that test the model’s ability to represent convection, transport, and wet and dry deposition in a physically realistic way. Model results compare well with ²²²Rn measurements taken off of the coast of Northern California in 1994.

IMPACT has also been used to study the photochemical cycles of important tropospheric species such as CO, CH₄, NO_x, OH, and O₃. Because IMPACT can be run using actual data-assimilated meteorology, we can compare our model results with observations. Currently, we are comparing model results using a "background" chemistry mechanism and 1997 meteorology with measurements from the NASA SONEX and NOAA NARE campaigns, conducted in the fall of 1997 over the Atlantic Ocean.

Our model shows that synoptic-scale events may lead to periods during which North American emissions strongly affect the air quality over the North Atlantic Ocean, as well as periods during which European emissions may contribute significantly.

Significance

Our model is now being used to simulate actual time periods of sampling campaigns. We are comparing model results with measurements to identify areas for model improvement. Our model can also predict the effect different regions have on air quality on regional, hemispheric, and global scales. Because of this, we can also predict how future changes in emissions will affect air quality on these same scales.

Publications

C. Atherton, D. Bergmann, C. Chuang, P. Connell, J. Dignon, D. Kinnison, D. Proctor, D. Rotman, and J. Tannahill, "IMPACT: A three-dimensional model for combined tropospheric and stratospheric chemistry studies," Joint International Symposium on Global Atmospheric Chemistry, Seattle, (IGAC/CACGP) August 1998.

C.Atherton, D. Bergmann, B. Chatfield, C. Chuang, P. Connell, J. Dignon, D. Kinnison, D. Proctor, D. Rotman, and J. Tannahill, "Fate of continental emissions: Three-dimensional global modeling results for 1997," submitted to the American Geophysical Union Fall Meeting, San Francisco, December 1998.

C. Atherton, D. Bergmann, P. Connell, J. Dignon, and D. Rotman, "Using global models and measurements to characterize the North American atmosphere," submitted to the American Meteorological Society 79th Annual Meeting, Dallas, TX, January 1999.