In August 2017, a smoke plume from wildfires in British Columbia and the
Northwest Territories recirculated and persisted over northern Canada
for over two weeks. We compared a full-factorial set of NASA Goddard
Institute for Space Studies ModelE simulations of the plume to satellite
retrievals of aerosol optical depth and carbon monoxide, finding that
ModelE performance was dependent on the model configuration, and more so
on the choice of injection height approach, aerosol scheme and biomass
burning emissions estimates than to the choice of horizontal winds for
nudging. In particular, ModelE simulations with free-tropospheric smoke
injection, a mass-based aerosol scheme and high fire NOx emissions led
to unrealistically high aerosol optical depth. Using paired simulations
with fire emissions excluded, we estimated that for 16 days over an 850
000 km2 region, the smoke decreased planetary boundary layer heights by
between 253 m and 547 m, decreased downward shortwave radiation by
between 52 Wm-2 and 172 Wm-2, and decreased surface temperature by
between 1.5 oC and 4.9 oC, the latter spanning an independent estimate
from operational weather forecasts of a 3.7 oC cooling. The strongest
surface climate effects were for ModelE configurations with more
detailed aerosol microphysics that led to a stronger first indirect
effect.