NARR-based Wind and Pasquill Stability Class Climate Dataset

In this study, a North American Regional Reanalysis (NARR; Mesinger et al. 2006)-based wind and Pasquill stability class climate dataset was developed for the North American Great Lakes region. Motivated by the need to update the limited wind and Pasquill stability class climatology previously incorporated into a livestock odor nuisance-mitigation application used in Michigan, this study was motivated more generally by the lack of a long-term climate dataset suitable for studies of atmospheric dispersion in the Great Lakes region. As a preliminary step, NARR 10-m wind speed, 10-m wind direction, and 2-m temperature were evaluated at eight weather stations in Michigan and northern Indiana, and the wind speed variable was subsequently bias corrected. To derive a Pasquill stability class dataset from the NARR variables, an existing empirical relationship between Pasquill stability class and Richardson number was applied to a previously developed NARR-derived Richardson number dataset covering the period 1979-2008 (Heilman and Bian 2013). Pasquill stability class frequency in NARR was subsequently evaluated using observations at two flux towers in Illinois. Although a tendency was noted for the NARR-derived Pasquill stability class dataset to underestimate the frequency of stable and unstable conditions, and overestimate the frequency of neutral conditions, the 10-m wind speed bias correction procedure was found to yield a frequency distribution in better agreement with the observations than the non–bias-corrected dataset. Caution is recommended regarding the applicability of the NARR-based dataset. Because the 10-m wind speed bias correction was based on data from weather stations sited in Michigan and northern Indiana, and the assessment of the NARR-derived Pasquill stability class dataset was performed with data from flux tower sites in central and northern Illinois, confidence in the accuracy of the NARR-based wind and Pasquill stability class climate dataset diminishes with distance from the area comprising Michigan and the northern portions of Indiana and Illinois.