Aerosol Shortwave Radiative Heating and Cooling by the 2017 and 2023 Chilean Wildfire Smoke Plumes

• Published in: Geophysical research letters 2023-11, Vol.50 (22), p.n/a
• Main Authors: Graaf, Martin, Tilstra, L. Gijsbert, Stammes, Piet
• Format: Article
• Language: English
• Subjects: Aerosols; Atmosphere; Clouds; clouds and aerosols; Computation; Drought; Dry periods; Heating and cooling; Optical thickness; Plumes; radiation: transmission and scattering; Radiative heating; radiative processes; Radiative transfer; remote sensing; Satellite observation; Satellites; Short wave radiation; Smoke; Smoke effects; Smoke plumes; Solar radiation; Vertical distribution; Vertical stability; Wildfires
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL104387

The aerosol shortwave, direct radiative effects of smoke plumes from Chilean wildfires in 2017 and 2023 were derived from satellite observations in both cloud‐free and cloud scenes. At the top of the atmosphere, the aerosol DRE changes sign when aerosol overly clouds or open ocean, confirmed by both measurements and a simulation study. The cloud‐free daily‐mean DRE, computed using an offline radiative transfer model (RTM), was 66 W m−2 in 2023 and 42 W m−2 in 2017, due to absorption by smoke. However, the total radiative effects were larger in 2017 due to a larger plume size compared to 2023. The method presented here provides a new conceptual model to quickly assess the radiative effects of wildfire smoke plumes using satellite measurements and pre‐computed RTM results. The presented estimates are strongly affected by the uncertainty of aerosol optical thickness retrievals from satellite, which can be large in the presence of clouds. Plain Language Summary From 30 January to the end of February 2023, central Chile experienced over 400 individual wildfires, consuming over 430,000 ha of native sclerophyllous forests, with 25 fatalities as of 14 February. Wildfires are common in central Chile during dry periods, but seem intensified due to the mega‐drought since 2010. Next to health effects, the smoke from these wildfires has important climatic impacts through the change of solar insolation in the atmosphere: smoke strongly absorbs solar radiation and heats the atmosphere, changing the vertical stability. In this paper, the horizontal and vertical smoke distribution in the atmosphere is presented using satellite observations, and the radiative effects in the atmosphere and at the surface are quantified for the recent fires and as well as for the record‐breaking wildfires in 2017, which were the most devastating in the modern history of central‐Chile. Our results show that the radiative effects of the smoke from the recent wildfires were stronger in magnitude during the first few days, but confined to a smaller area, reducing their overall effect. Key Points The radiative effects of the recent 2023 Chilean wildfire smoke plumes are assessed and compared to the 2017 Chilean wildfires smoke plumes Pre‐computed radiative transfer model results can provide readily available aerosol direct radiative effects in clear‐sky for smoke Satellite measurements can further improve the aerosol direct effect and direct forcing estimates for both clear sky and cloud scenes