2.6 Using CAPTEX data in this tutorial




In most of the following sections the trajectory and air concentration 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 perflurocarbon (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 hour duration after each release.

The primary meteorological data used in most calculations will be the North American Regional Reanalysis (NARR) available at 32 km horizontal resolution every three hours. The meteorological data for this experiment are provided as part of the HYSPLIT distribution. The Gridded Binary (GRIB) files for the NARR for other time periods can be downloaded from the NOMADS web page. When selecting data to download, all variables and cycles should be obtained. Converting meteorological data from GRIB1 to a format HYSPLIT can process will be discussed in later sections.

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 other examples, the individual 3- or 6- hourly average concentrations will be used for the analysis.