Exercise #16

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  • Problem #1 - In the previous example, a customized EMITIMES file was created with three 12-h emission time groups. Edit the file so that only one time group is defined for the 36-h emission period.

  • Hint - Start with the EMITIMES and CONTROL files that were created in the previous example and should still be found in /hysplit/working directory.

  • Solution - After editing the EMITIMES and CONTROL files, simply rerun the model ..\exec\hycs_std and graphics display program ..\exec\parxplot -iPARDUMP -k1 -z80 from the command prompt. Although the particle plots look almost identical, the new single emission cycle simulation shows 6565 particles at the end while the previous three-cycle simulation showed 17181 particles. Why are there three times fewer particles in the single cycle simulation?


  • Problem #2 - Just using the information given for the calculation in problem #1, estimate the depth of the deposition layer in the region a few hundred kilometers downwind of the volcano.

  • Hint - Add the deposition layer and use a finer concentration grid, use more particles (you may want to limit the duration, khmax=8, for a faster calculation), and estimate the conversion factor required to convert ug/m2 to cm by assuming a lower density than the particle value used in the calculation.

  • Solution - The concentration display menu may take a little manipulation to get a nice looking graphic and correct labels require the creation of a LABELS.CFG file. The maximum value of 0.0037 cm just downwind is only a crude estimate because of the short duration calculation, uncertainty in the emission rate, and particles larger than 20 um were not included in the calculation.