Wildfire Aerosol and Cloud Radiative Forcing in the Mackenzie River Basin from Satellite Observations

Abstract

Clouds and wildfire aerosols are both important in our understanding of the radiation budgets in the Mackenzie River Basin (MRB). The smoke aerosols produced by wildfires are predominately aerosols that can absorb incoming solar radiation in the atmosphere. Both the cloud and wildfire aerosol radiative forcing at the top of atmosphere (TOA) and at the surface in the MRB are investigated. Second-order polynomial relationships are found between forcing ( Δ F) and aerosol optical thickness (τ) for the reflected solar fluxes at the TOA, the outgoing longwave (LW) fluxes at the TOA, and the net surface solar fluxes. The monthlymean basin-average cloud shortwave forcing at the TOA and at the surface between June and September are between 150 and 200Wm-2 and -160 and -220 W M-2, respectively, while the basin-averaged outgoing LW cloud forcing at the TOA is around -40 W m-2. Overall, the cloud forcing could impact the shortwave and longwave radiation budgets by 30–50% both at the TOA and at the surface for the MRB region.