Air Dispersion Modeling via the Internet

Technological advancements have revolutionized air dispersion modeling practice over the last 15 years. Through the 1980s and 1990s, computers became faster, smaller, and easier to use. Major permitting work could be completed more quickly. Software utility programs became readily available, improving the ability of modelers to process and visualize data.

The Internet has had a profound effect on air dispersion modeling practice. Already, the tools and information that dispersion modelers use, such as the models, meteorological data and topographical maps, can be obtained over the Internet. Model users now typically either download models such as ISCST3 from the USEPA SCRAM web page, or purchase dispersion model suites from software firms. Thus, models have become distributed across many local computers.

This paper examines the feasibility of running air dispersion models such as ISCST3 or AERMOD over the Internet. Under a centralized model, users would no longer need to run EPA FORTRAN code locally, or purchase and install proprietary software on a local computer. Instead, users would interact with an Internet interface, uploading model input data or entering data into forms, and retrieving or downloading model output results. Model code, not necessarily FORTRAN-based code, would be run remotely on very fast servers.

A major advantage to running dispersion models over the Internet would be convenience and time savings. For example, a new model user might be trained to use ISCST3 quickly in an online interactive format. Large modeling jobs could be completed very quickly; critical for time-sensitive permitting projects. The model user would count on the Internet modeling system to work without the possible burden of troubleshooting local computer problems. Added value could be provided to model users through a meteorological data library and online graphical data visualization. On a monthly subscription basis, an online dispersion modeling system that offers interactive training might be a cost-effective alternative for many model users.

Dispersion modeling over the Internet could be subject to several limitations, which will be examined in this paper. Since dispersion modeling usage is driven by regulatory agencies, an Internet modeling system would need to conform to equivalency tests. This would be true especially if FORTRAN code is converted to be more Internet-friendly non-DOS code. There would be a fixed limit to how many model runs could be queued remotely on a single server at the same time. Internet use will continue to be limited by data transfer speeds. These are issues the computer industry at large is facing as computers become more linked, or networked, and software applications become more centralized. Despite the limitations, these changes will continue to shape the way air pollution meteorologists practice dispersion modeling.