8.2 Air Concentration Display Options




Do not proceed with this section unless the previous section has been completed and you have created two different output files in the working directory for CAPTEX release #2: hysplit2.bin with 3-hour average air concentrations and PARDUMP with all the particle positions every 3 hours.

  1. Press the Display / Concentration / Contour menu tab to open the concentration display menu. Only a few changes are required from the defaults. Because we defined the release rate in grams and we know that the measured concentration data are reported in pico-grams per cubic meter, we need to define a concentration multiplier of 1.0E+12, the number of pg in each gram. The air concentration label field should also be changed from blank to pg. If desired, increase the zoom to reduce the whitespace around the plot.

  2. The Postscript viewer opens automatically and then you can scroll though the images frame-by-frame. The plot after 12 hours shows a very similar pattern to the test plots done in previous sections. The plot is not identical to the one shown in the introductory section where the contour values were fixed rather than letting the contouring program automatically select the interval. To animate the multi-frame Postscript file, press the Utilities / Postscript to Image menu tab to open the conversion menu. Set the Animate and Crop radio-buttons and increase the slider bar for better resolution if desired. When the menu disappears, the animated GIF graphic will be found in the /working directory. Although different graphic conversions can be specified by changing the output file suffix, only GIFs can be animated.

  3. To follow the individual particle trajectories, press the Concentration / Display / Particle menu tab to open the particle display menu. There are four radio-button options: 1) a horizontal plane view, 2) a vertical West->East and South->North projection, 3) a global projection, and 4) the default combination plane-view with a cross-section. Perhaps increase the zoom, but otherwise select the default options, and the viewer will open the multi-frame file partplot.ps (depending upon the speed of your computer, this may take several minutes - for quicker results plot every 10th particle), which like all other output files, unless otherwise directed, is located in the /working directory. Skip to the frame representing the particle positions after about 12 hours and the image will show all the particle positions that contributed the 3-hr average air concentration map. Try the other particle display options to see the differences and perhaps create a particle animation.

  4. To examine the temporal evolution of the released tracer, press the Concentration / Display / Arrival menu button to open the plume arrival time menu which will create a color-filled graphic representing the time after sampling has started that a grid cell shows a non-zero concentration. The menu permits setting a threshold concentration other than zero, as well as setting the number of contours and the time difference between contours. For this example, change the time difference from -1 (auto select) to 6 hours. The resulting output file toa.ps shows arrival times to the east coast of 42 hours. Only files with multiple time period output can be analyzed for arrival times.

  5. Another display option is to see the concentration values in each grid cell without the interpolation and smoothing introduced by the contouring program. Press the Display / Concentration / Grid Values menu tab to open the grid cell display menu. The default values are set to display the full range of potential concentrations. Change the contour base (the minimum) to 1.0E-10 and the contour delta to 2.0. With the log scale box checked, the 2.0 is interpreted such that each color interval will be a factor of two larger than the previous one starting with the base value. The multi-frame postscript file shows the concentration value in each grid cell as one frame per time period.

The concentration display options reviewed in this section all create Postscript files that can be directly printed or converted to other formats. Some of the display menus also contained other options that would create GIS compatible output files such as ESRI Shapefiles and Google Earth KML. These options will be explored in more detail in later sections.