2.5 Using CAPTEX data in this tutorial

In most of the following trajectory and air concentration sections, examples will be based on a real event where the pollutant emission rate is known and air concentrations have been measured at numerous locations. The tutorial focus will be on the second release of the Cross Appalachian Tracer Experiment. CAPTEX (Ferber et al., 1986) consisted of six 3h perfluorocarbon (C7F14) tracer releases (September 18th to October 29th, 1983), four from Dayton, Ohio and two from Sudbury, Ontario, Canada. Samples were collected at 84 sites, 300 to 800 km from the source, over 3 h and 6 h averaging periods, for about a 48 to 72 hour duration after each release.

The primary meteorological data used in most calculations will be the Weather Research Forecast (WRF) model especially configured for CAPTEX by Ngan and Stein (2017) to use the UW boundary layer, Monin‐Obukhov surface layer, and the Noah land surface model. Initial and boundary conditions were provided by the North American Regional Reanalysis (NARR). The WRF data fields are available hourly at a horizontal resolution of 27 km.

To aid in the interpretation of the various modeling techniques that will be introduced in the tutorial, you can view the HYSPLIT simulation for CAPTEX release number 2. The animation shows the sequence of model calculated three hour average concentration patterns (in units of pg/m³ - pico grams per cubic meter) superimposed over the measured air concentrations averaged over the three day duration of the experimental sampling for release #2. In most other examples, the individual 3- or 6- hourly average concentrations will be used for the analysis.