Files of hourly NO2 and SO2 concentrations from NDDoH monitoring sites listed above may be used as hourly background concentrations directly input to AERMOD or may be used to calculate other types of background values, e.g., annual, seasonal, or monthly averages. Monitoring sites with data in these folders represent the NDDoH's preferred sites for providing background concentration data, even though data from other monitoring sites may be used.
Files with designation "0408S2" have substitutions entered for all missing hours. Therefore,
use of these hourly background files are preferred for use with NDDoH post-processing software.
Somewhat because of recent EPA guidance on background concentrations used with the new 1-hour NAAQS, the NDDoH does not recommend using hourly concentration data as a first choice for use in regulatory AERMOD modeling in North Dakota. For this reason, the background NO2 and SO2 concentration data listed above have not been updated with 2009-2013 monitoring data.
The NDDoH currently prefers use of a constant background concentration or input of matrices of seasonal, monthly, diurnal, or similar concentrations for use with AERMOD as a 1st and 2nd Tier background. Use of hourly monitoring data as background concentrations input to AERMOD will be considered on a case-by-case basis. Please contact the NDDoH Modeling Program for further information about options for background data.