In response to increasing concerns about air quality downwind of animal operations within the state, the Oklahoma Dispersion Model (ODM) is a operational tool that has been developed to aid in assessing the atmosphere's ability to disperse gases and small particulates that are released near the ground. Besides odors associated with animal operations, other examples include smoke from prescribed burns and pesticides from land or aerial application.

The Model generates both graphical and text output that depict current and future conditions for atmospheric dispersion (dilution of plume) and transport direction (direction of plume movement). A Gaussian plume model is employed to evaluate dispersion conditions with respect to downwind concentrations in the 1/4 mile to 2 mile range. The ODM can thus be used to better assess appropriate times to minimize downwind pollutant concentrations resulting from activities such as land application of animal waste, pesticide application, or a prescribed burn.

Weather data from the Oklahoma Mesonet, the state's automated weather station network (115 stations), are utilized to generate statewide maps showing current dispersion conditions and transport direction; these maps, available in near-real-time, are updated every 15 minutes. The dispersion maps feature a five-color classification scheme for dispersion conditions: excellent, good, moderate, poor, and very poor. Corresponding maps for transport direction utilize a station plot of temperature, relative humidity, wind speed, and wind direction. With respect to future conditions, the latest NGM (Nested Grid Model) MOS (Multiple Output Statistics) forecasts for specific sites within and surrounding Oklahoma are used to generate similar maps valid at 3-hour increments throughout the 60-hour forecast period; these maps are updated every 12 hours. ODM output is easily available on the Web at:

http://agweather.mesonet.ou.edu/models/dispersion

This paper will discuss details of the Oklahoma Dispersion Model, present examples of graphical and text output from the Web site, and show how the model can be used as a management tool for timing near-surface releases of gases and small particulates.