Development of a NARR-based wind and atmospheric stability class climatology for use with a Michigan livestock odor compliance tool (MI Odor Print)

MI Odor Print is a planning tool for assessing potential odor impacts from livestock facilities that is used by the State of Michigan to verify regulatory compliance for planned livestock facilities. The output, called an odor footprint, is a radial plot which represents approximate distances that one must be away from an odor source to detect a noticeable or stronger odor up to 1.5%, 3% and 5% of the time for each of the 16 compass directions. MI Odor Print is based on the Odor from Feedlot – Setback Estimation Tool (OFFSET) model, a model for determining appropriate setback distances between neighboring residents and livestock farms in order to ensure acceptable air quality [Jacobson et al. 2005, Development of the OFFSET model for determination of odor-annoyance-free setback distances from animal production sites: Part I. Review and experiment. Trans. ASAE, 48, 2259−2268]. OFFSET was developed using odor measurements at 85 Minnesota farms, limited meteorological data, and a puff dispersion model. Whereas OFFSET is based in part on nine years of observations from six Minnesota weather stations, MI Odor Print was adapted for use with Michigan farms using nine years of data from eight Michigan weather stations. MI Odor Print, last updated over 15 years ago, is a one-size-fits-all tool that, like OFFSET, implicitly assumes that wind and atmospheric stability climatologies are spatially uniform across the state. This presentation describes a recent effort to update the source of wind and atmospheric stability in MI Odor Print to both cover a longer time period and account for known spatial variability in wind and stability climatologies across Michigan. To this end, the North American Regional Reanalysis (NARR) is used to develop a 30-year dataset [1979-2008] of Pasquill stability class, wind speed, and wind direction. Note that the spatial coverage of this dataset is identical to that of NARR, covering North America, although the dataset was validated for the Midwest region only and was developed specifically for Michigan. The outline of this presentation is as follows. First, the procedure developed for deriving Pasquill stability class from NARR output variables is detailed; second, validation of the dataset and a subsequent wind speed bias correction procedure are described; and third, an assessment of the spatial and temporal variability of odor footprints across Michigan is presented, including a corresponding assessment of wind and atmospheric stability climatologies.