Primary OC/EC ratio calculator (POERC)

Note: this is an old program which had been replaced by MRS, so updates are not foreseen.

The elemental carbon (EC) tracer method is a widely applied approach in estimating secondary organic carbon (SOC) from observation data of EC and organic carbon (OC). The key issue for the EC tracer method is to identify an appropriate OC/EC ratio that represents primary combustion emission sources (i.e., (OC/EC)_pri) for the observation site. Conventional approaches include assigning a fixed percentile subset with the lowest OC/EC ratio (usually 10~20%) or relying on a subset of sampling days dominated by local emissions and with low photochemical activities. The drawback of these approaches is lack of clear quantitative criteria in the selection of data subsets for the (OC/EC)_pri determination. Minimum R Square Method (MRS) proposed by Millet et al. (2005) has a clear quantitative criterion for (OC/EC)_pri calculation. To facilitate the application of MRS, a handy tool is developed which is called “Primary OC/EC ratio calculator (POERC)”. POERC is written in Igor Pro (WaveMetrics, Inc. Lake Oswego, OR, USA) to provide easy-to-use graphic user interface. POERC is designed to perform OC and EC data analysis from time resolved observation, especially focus on determining (OC/EC)pri using tracer ratio method.

Millet, D. B., Donahue, N. M., Pandis, S. N., Polidori, A., Stanier, C. O., Turpin, B. J., and Goldstein, A. H.: Atmospheric volatile organic compound measurements during the Pittsburgh Air Quality Study: Results, interpretation, and quantification of primary and secondary contributions, Journal of Geophysical Research: Atmospheres, 110, D07S07, 10.1029/2004jd004601, 2005.