Estimating the Impact of a 2017 Smoke Plume on Surface Climate Over Northern Canada With a Climate Model, Satellite Retrievals, and Weather Forecasts

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 comparatively high fire NOx emissions led to unrealistically high aerosol optical depth. Using paired simulations with and without fire emissions, we estimated that for 16 days over an 850,000 km2 region, the smoke decreased planetary boundary layer heights by between 253 and 547 m, decreased downward shortwave radiation by between 52 and 172 Wm-2, and decreased surface temperature by between 1.5 degrees C and 4.9 degrees C, the latter spanning an independent estimate from operational weather forecasts of a 3.7 degrees C cooling. The strongest surface climate effects were for ModelE configurations with more detailed aerosol microphysics that led to a stronger first indirect effect. Smoke from biomass burning is known to have effects on surface weather. We used the NASA GISS ModelE to estimate these effects for a large 2017 smoke plume over northern Canada that persisted for two weeks. We first found that the height of the smoke release at the source was the most important factor influencing agreement between ModelE and satellite retrievals of aerosols and carbon monoxide, and that specific, plausible configurations of the model led to unrealistically high aerosol amounts. By comparing simulations with and without fire, we estimated a 16-day cooling over a 850,000 km2 region of between 1.5 degrees C and 4.9 degrees C, depending on the model configuration. We captured the overall pattern and magnitude of a large 2017 smoke plume over Canada with the NASA GISS ModelE Of the sixteen plausible model configurations tested under a full-factorial design, two with higher NOx emissions, free-tropospheric smoke release and mass-based aerosols led to unrealistically high aerosol optical depth Over an 850,000 km2 region, we estimated a 16-day surface cooling of between 1.5 degrees C and 4.9 degrees C