ARL Weekly News – October 26, 2018

The 17th Annual Community Modeling and Analysis System (CMAS) Conference, sponsored by the U.S. Environmental Protection Agency, was held between October 22 and 24, 2018 in Chapel Hill, North Carolina. ARL led and contributed to 10 presentations. Youhua Tang, Tianfeng Chai and Daniel Tong focused on emission modeling and gave the following presentations: “HI volcanic eruption,” “inversion modeling for smoke utilizing satellite data and HYSPLIT trajectories,” and “new development of the FENGSHA dust emission model,” respectively. Barry Baker presented a poster titled “A python-based evaluation system for predicted meteorological and atmospheric chemical constituents.” Pius Lee led a talk on “Potential performance change when the National Air Quality Forecasting Capability (NAQFC) is upgraded in near and medium-range terms.” Hyuncheol Kim gave two presentations on NOx-measurement, including demonstration of a mass consistency scheme and emission estimation using data training techniques.The aforementioned scientists also contributed to three other NAQFC related talks: the National Weather Service’s Ivanka Stajner talked about “Recent NAQFC updates,” the Environmental Modeling Center’s Jianping Huang presented “A FV3-based AQ forecast at NOAA,” and Sonoma Tech’s Kenneth Craig talked about “Estimation of biomass burning location and duration using ground-crew reports.” These contributions were favorably received. For more information, please visit:

As mentioned in previous reports, FRD has been revisiting its capability to measure multiple tracers released simultaneously. Several years ago, the division developed a rudimentary method to measure three perfluorocarbon tracers from the same bag samples. However, this method was complicated and required a mixture of helium and argon as a carrier gas. Tests over the past week have indicated that nitrogen can be substituted for the helium and argon. This means that a greatly simplified method can be developed to measure the perfluorocarbons at parts per trillion level, since nitrogen is also the standard carrier gas used with the workhorse SF6 tracer.

An improved perfluorocarbon method will still be more difficult than SF6, because these tracers come out of the gas chromatograph columns after oxygen, which means longer analysis times. Backflushing of the columns after the introduction of samples is also not as efficient with the perfluorocarbons. A calibration standard for the fourth-generation refrigerant HFC-1234ze has been ordered to perform preliminary tests for suitability as a tracer. Little is known about these refrigerants regarding such fundamental issues as optimal columns, retention times, and their limits of detection.