New Meteorological Data Available for Dispersion Modeling
Posted: 02/22/2012

New meteorological data suitable for use in EPA’s AERMOD dispersion model are now available for use in regulatory applications in the state of Iowa. These data may be downloaded from the Air Quality Bureau’s preprocessed meteorological data webpage.

These data consist of 19 five-year sets for the period 2005 – 2009. The meteorological stations include Ames, Burlington, Cedar Rapids, Davenport, Des Moines, Dubuque, Estherville, Iowa City, La Crosse, Lamoni, Marshalltown, Mason City, Moline, Omaha, Ottumwa, Sioux City, Sioux Falls, Spencer and Waterloo. Nine new sites have been added that were not included in the 2000 – 2004 datasets.
The new sites provide additional refinement to the representativeness of the data to various areas of the state. A map depicting the areas of the state represented by each of the data sets and a technical support document are available on the website.
Changes to the locations represented by several meteorological stations, as well as recent upgrades to EPA’s meteorological data preprocessor (AERMET) and the inclusion of one minute wind data using the EPA’s new AERMINUTE preprocessor have resulted in the 2005 – 2009 data being substantially different from the 2000 – 2004 data.
The sensitivity of AERMOD to the changes being introduced by the new meteorological data was tested. On average, users can expect concentrations to increase for the shortest averaging periods (1-hour and 3-hour), and to decrease for the longer averaging periods (8-hour, 24-hour and annual). A more detailed sensitivity analysis is available within the technical support document on the website.
Applicants should begin using the new meteorological data immediately. However, the 2000 – 2004 data will remain available on the Department’s website until 6/30/2012, and may continue to be used in cases where it has been approved in a dispersion modeling protocol.
Questions or comments related to the meteorological data should be directed to Brad Ashton of the Air Quality Bureau's modeling group. He may be reached by phone at 515-242-6532, or by email at

This list serve article is intended for consultants, industries, environmental groups, general public, and other entities regulated under the Clean Air Act. It was written by the DNR Air Quality Bureau to share regulatory news, program updates and technical guidance.