Footprints are generated using the Lagrangian Particle Dispersion Model from 
Uliasz 1993. Twenty particles are released at each tower site every 30 seconds 
(2400 hourly) in each domain, and are tracked backwards in time using the 
respective meteorology of each domain until a particle has left its domain 
boundary or a total of 72 hours have elapsed. Meteorology was generated using 
a custom WRF-Chem run described in Davis et al 2017 
(https://doi.org/10.1525/elementa.188)

Domain 1 is largest domain (900x900 km). Domain 3 is smallest (100x100 km)

Domain 1 (d01) footprints are gridded at 9km resolution.
Domain 2 (d02) footprints are gridded at 3km resolution.
Domain 3 (d03) footprints are gridded at 1km resolution.

Locations of each tower and particle release can be found in the file 
tower-locations.csv