Transport of the 2017 Canadian wildfire plume to the tropics and global stratosphere via the Asian monsoon circulation

Abstract : We show that a fire plume originating at high northern latitudes during the Canadian wildfire event in July/August 2017 reached the tropics, and subsequently the tropical stratosphere via the ascending branch of the Brewer-Dobson Circulation (BDC). The transport from high to low latitudes in the upper troposphere and lowermost stratosphere was mediated by the anticyclonic flow of the Asian monsoon circulation. The fire plume reached the Asian monsoon area in late August/early September, when the Asian Monsoon Anticyclone (AMA) was still in place. While there is no evidence of mixing into the center of the AMA, we show that a substantial part of the fire plume is entrained into the anticyclonic flow at the AMA edge, and is transported into the tropical Upper-Troposphere–Lower-Stratosphere (UTLS), and possibly the Southern Hemisphere particularly following the north-south flow on the eastern side. In the tropics the fire plume is lifted by ~1.5 km per month. Inside the AMA we find evidence of the Asian Tropopause Aerosol Layer (ATAL) in August, doubling background aerosol conditions with a calculated top of the atmosphere shortwave radiative forcing (RF) of −0.05 W/m2. The regional climate impact of the fire signal in the wider Asian monsoon area in September exceeds the impact of the ATAL by a factor of 2–4 and compares to that of a plume coming from an advected moderate volcanic eruption. The stratospheric, trans-continental transport of this plume to the tropics and the related regional climate impact point at the importance of long-range dynamical interconnections of pollution sources.
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Submitted on : Tuesday, November 5, 2019 - 10:53:43 AM
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Corinna Kloss, Gwenaël Berthet, Pasquale Sellitto, Félix Ploeger, Silvia Bucci, et al.. Transport of the 2017 Canadian wildfire plume to the tropics and global stratosphere via the Asian monsoon circulation. Atmospheric Chemistry and Physics Discussions, European Geosciences Union, 2019, (preprint: 22 p.). ⟨10.5194/acp-2019-204⟩. ⟨hal-02347313⟩

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