Code for using the hysplit back trajectory model.
first download the hysplit model as described in: https://bookdown.org/david_carslaw/openair/sections/appendices/appendix-hysplit.html
01_hysplit.R is an adaption of this gist: https://gist.github.com/davidcarslaw/c67e33a04ff6e1be0cd7357796e4bdf5