Keeping the Increasing Complexity of Air Dispersion Modeling in Check

Driven by advances in scientific knowledge, tightening and constantly changing regulations, and higher-resolution raw data, environmental modeling is demanding more and more from EH&S professionals and their computers. AERMOD run times for large projects are measured in days rather than minutes and terrain data file sizes routinely exceed 100 MB. Modelers can increase productivity and keep the increasing model complexity under control with a number of tools from BREEZE Software.

Reduce ballooning AERMOD run times

The advanced physics in U.S. EPA’s AERMOD model come with the disadvantage of substantially increased model run times. Even for a relatively small project with a few thousand receptors and a dozen sources, run times can easily be longer than one hour, making the process of model refinements (e.g., testing the impact of a stack height change) cumbersome. Run times can be several days for larger runs involving hundreds of sources. To address this issue, the BREEZE Software group has developed BREEZE AERMOD Parallel, which takes advantage of the multi-core processors found in most modern computers to dramatically decrease AERMOD run times. A two-core version, which can nearly double the speed of an AERMOD run, is included with every copy of BREEZE AERMOD and four- and eight-core versions are available for purchase for those who have more powerful machines.

For very large AERMOD runs or for smaller, highly time-sensitive runs, the BREEZE Remote Modeling System (BRMS) provides the fastest possible results. Up to 100x faster than a normal one-processor AERMOD run! Both BREEZE AERMOD Parallel and BRMS produce identical results to the U.S. EPA AERMOD executable.

Staying on top of changes to meteorological data processing standards

Meteorological data processing has never been an easy task. The process involves many tedious steps that can be time-consuming and perplexing, even for the seasoned individual. Additionally, the modeling options and regulatory guidelines applicable to meteorological data processing are changing on a regular and frequent basis. For example, the treatment of low wind speeds has changed several times since 2011, and more changes are expected with the next release of AERMOD/AERMET. From climatological normal precipitation data to 1-minute wind speed data, the amount of information that must be obtained and synthesized in meteorological data processing continues to grow as well.

The BREEZE Software data team, which consists of staff meteorologists, environmental engineers, and modeling experts, can process meteorological data quickly and properly for any location in the world. Many modelers find the model-ready meteorological data provided by BREEZE to be a cost-effective alternative to the hassle of processing the data themselves. Because the BREEZE data team stays up to date with U.S. regulatory requirements, as well as innovative techniques for generating accurate AERMOD-ready data for remote locations, this data can be used with confidence for regulatory modeling.

Recent regulatory model updates with more coming this Fall
  • AERMOD: U.S. EPA’s most recent update to the AERMOD system was in December 2012 with active development ongoing this year. Some of the most exciting potential developments for modelers are the expected changes to the handling of low wind speeds for low level releases, a situation in which AERMOD has been shown to over predict concentrations. An updated release of AERMOD and the AERMET meteorological preprocessor is expected from EPA before the end of the year. It remains to be seen whether the sequester and government shutdown will delay those plans. As soon as EPA releases a new AERMOD version, BREEZE will incorporate it into BREEZE AERMOD. The BREEZE team was able to release an updated version of BREEZE AERMOD including the model update within a week of EPA’s December release.
  • CALPUFF: The CALPUFF model is undergoing continuous development. From the modeler’s perspective, this is complicated by the existence of two versions of the CALPUFF system: the most recent release from the model’s developer and the most recent version that has been fully tested and approved by U.S. EPA for regulatory use. The most recent version of both the model developer’s CALPUFF and the U.S. EPA-approved CALPUFF are included in BREEZE’s upcoming CALPUFF Professional 2.1 release.

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