North America Tracer Experiment - ANATEX

Inert atmospheric tracers provide excellent benchmarks for testing atmospheric dispersion models. Most long-range experiments have been conducted under very controlled conditions (preselected meteorological conditions), leading to the question of how that might be biasing the statistical evaluation of the dispersion models. This problem was addressed in the Across North America Tracer Experiment (ANATEX - Draxler et al., 1991) in which two different inert perfluorocyclohexane gases (PTCH and oPDCH) were released for three hours from two different locations, Glasgow, Montana (GGW - 48.4N, 106.5W) and St. Cloud, Minnesota (STC - 45.6N, 94.2W) every 2« days with about 75 samplers located at weather stations over the whole eastern half of the U.S. The experiment last three months, from January 5th through March 29th of 1987.

Research Summary The HYSPLIT model was run for each dispersion combination independently for each source location. The first half of the experimental period was selected for analysis. The model was configured to run for 814 hours, starting with the first release on the 5th of January and ending on the 8th of February. A period which would include 14 tracer releases from each location. An illustration of the results for the top-hat/particle combination for GGW is shown for both measured and calculated concentrations. Concentration units are 10-12 g m-3 and the contours are drawn at levels of 10, 20, 50, 100, and 200 units. The basic over-calculation can be seen in that the inner calculated contours cover larger area than the measurements. Calculations at more distance sources seem reasonable. Because this is a winter period, more stable atmospheric structure should increase the model's sensitivity to the vertical mixing computation method. In contrast if the BL is well mixed it would matter little if the model mixed pollutants twice as fast or slow as it should at these longer travel distances. Future Activities The experimental data will be integrated into a master data base of all ARL sponsored long-range tracer experiments available over the Web and on CD ROM. In conjunction with a standard set of meteorological fields, the concentrations will be used to test various dispersion modeling parameterizations. Click here to download data and reports.

References

Draxler, R.R., 1991: The accuracy of trajectories during ANATEX calculated using dynamic model analyses versus rawinsonde observations. J. Appl. Meteorol., 30: 1446-1467.

Draxler, R.R., R. Dietz, R.J. Lagomarsino, and G. Start, 1991: Across North America Tracer Experiment (ANATEX): Sampling and analysis, Atmos. Environ., 25A: 2815-2836.

Draxler, R.R., and J.L. Heffter (Eds), 1989: Across North America Tracer Experiment (ANATEX) Volume I: Description, Ground-level sampling at primary sites, and meteorology. NOAA Tech Memo ERL ARL-167, Air Resources Laboratory, Silver Spring, MD, 83 p.

Draxler, R.R., 1988: Across North America Tracer Experiment (ANATEX) weather maps and tracer concentrations. NOAA Tech Memo ERL ARL-165, Air Resources Laboratory, Silver Spring, MD, 87 p. Heffter, J.L., and R.R. Draxler, 1989: Across North America Tracer Experiment (ANATEX) Volume III: Sampling at tower and remote sites. NOAA Tech Memo ERL ARL-175, Air Resources Laboratory, Silver Spring, MD, 67 p.

Stunder, B.J.B., and R.R. Draxler, 1989: Across North America Tracer Experiment (ANATEX) Volume II: Aircraft-based sampling. NOAA Tech Memo ERL ARL-177, Air Resources Laboratory, Silver Spring, MD, 29 p.