Role of Complex terrain on transport and dispersion

• in complex terrain, there are four basic scenarios that contribute to high ambient concentrations [OH Hanna and Strimatis 6.1]:
  • plume impingement
  • pooling in valleys [OH Boubel 18-3, Whiteman 2.27]. Prince George Valley Fog image
  • downslope/down valley drainage of dense gas
  • channeling of the plume by terrain. Taylor BC inversion
• most local wind systems in complex terrain will have some impact on transport and dispersion of air pollution [OH Carruthers and Hunt 5.1]
• this is especially true of those features which involve circulations due to their
  • low wind speeds
  • potential to recycle air
  • diurnal reversals - pollution comes back
• These circulations can be thermally driven (under slack synoptic conditions):
  • [OH sea breeze, LFV ozone] sea/land breeze
  • [OH Oke 5.11] mtn/valley winds
  • [OH Boubel 17-20] katabatic / anabatic flows
• circulations forced by the interaction of synoptic winds with terrain can also impact AQ [OH Oke 5.16, 5.17]
• advective effects over non-homogeneous surfaces can impact AQ [OH Oke 9.10]