The NCAR Eulerian Regional Acid Deposition Model

The principal objective of this project is to develop an Eulerian regional acid deposition model suitable for assessing source-receptor relationships. The initial task is the construction of a modeling framework integrating an existing and evolving mesoscale meteorological model with a new transport and chemical transformation model. This report summarizes progress from May 1983 to December 1984. In a nutshell, the project is on schedule and, in selected areas, ahead of the original schedule (NCAR, 1983d). The mesoscale meteorological model has been recoded and is now about three times faster than before. Several scientific studies have been done using this state-of-the-art model. First-generation submodels of gas phase chemistry and aqueous phase chemistry with simple parameterizations of subgrid-scale cloud processing and dry deposition have been completed. Whenever possible, these submodels have been evaluated with or compared to available experimental data and found to be performing well. The submodels have been integrated into a first-generation Eulerian long-range transport and acid deposition model. A first run with the full modeling system using one set of Oxidant-Scavenging Characteristics of April Rains (OSCAR) data has been completed. The full set of OSCAR data is being analyzed in preparation for model evaluations. We have completed two exhaustive studies on the possible chemical reactions and aqueous phase reactions and evaluated the available data for reaction rate coefficients. We have also developed an analysis technique for studying source-receptor relationships within the Eulerian modeling framework. These studies and others are covered in this report.