Preprints
https://doi.org/10.5194/acp-2020-1240
https://doi.org/10.5194/acp-2020-1240

  28 Dec 2020

28 Dec 2020

Review status: this preprint is currently under review for the journal ACP.

Pyrocumulonimbus Events over British Columbia in 2017: The Long-term Transport and Radiative Impacts of Smoke Aerosols in the Stratosphere

Sampa Das1,2, Peter R. Colarco1, Luke D. Oman1, Ghassan Taha1,3, and Omar Torres1 Sampa Das et al.
  • 1NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
  • 2Universities Space Research Association-NASA Postdoctoral Program, Columbia, Maryland, USA
  • 3Universities Space Research Association, USRA, Greenbelt, Maryland, USA

Abstract. Interactions of meteorology with wildfires in British Columbia, Canada during August 2017 led to three major pyrocumulonimbus (pyroCb) events that resulted in the injection of large amounts of smoke aerosols and other combustion products at the local upper troposphere and lower stratosphere (UTLS). These plumes of UTLS smoke with elevated values of aerosol extinction and backscatter compared to the background state were readily tracked by multiple satellite-based instruments as they spread across the Northern Hemisphere (NH). The plumes resided in the lower stratosphere for about 8–10 months following the fire injections. To investigate the radiative impacts of these events on the Earth system, we performed a number of simulations with the Goddard Earth Observing System (GEOS) atmospheric general circulation model (AGCM). Observations from multiple remote-sensing instruments were used to calibrate the injection parameters (location, amount, composition, and heights) and optical properties of the smoke aerosols in the model. The resulting simulations of three-dimensional smoke transport were evaluated for a year from the day of injections using daily observations from OMPS-LP (Ozone Mapping Profiler Suite Limb Profiler). The model simulated rate of ascent, hemispheric spread, and residence time of the smoke aerosols in the stratosphere are in close agreement with OMPS-LP observations. We found that both aerosol self-lofting and the large-scale atmospheric motion play important roles in lifting the smoke plumes from near the tropopause altitudes (~12 km) to about 22–23 km into the atmosphere. Further, our estimations of the radiative impacts of the pyroCb-emitted smoke aerosols showed that the smoke caused additional warming of the atmosphere by about 0.6–1 W/m2 (zonal mean) that persisted for about 2–3 months after the injections in regions north of 40° N. The surface experienced a comparable magnitude of cooling. The atmospheric warming is mainly located in the stratosphere, coincident with the location of the smoke plumes, leading to an increase in zonal mean shortwave (SW) heating rates of 0.02–0.04 K/day during September 2017.

Sampa Das et al.

 
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Sampa Das et al.

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Pyrocumulonimbus Events over British Columbia in August 2017: Results from the NASA GEOS Earth System Model Sampa Das, Peter Colarco, and Luke Oman https://doi.org/10.25966/9FV8-6Q78

Sampa Das et al.

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Short summary
Interactions of extreme fires with weather systems can produce towering smoke plumes that inject aerosols at very high altitudes (> 10 km). Three such major injections, largest at the time in terms of emitted aerosol mass, took place over British Columbia, Canada in August 2017. We model the transport and impacts of injected aerosols on the radiation balance of the atmosphere. Our model results match the satellite-observed plume transport and residence time at these high altitudes very closely.
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