Influence of biogenic emissions from boreal forests on aerosol–cloud interactions

Abstract

Boreal forest acts as a carbon sink and contributes to the formation of secondary organic aerosols via emission of aerosol precursor compounds. However, these influences on the climate system are poorly quantified. Here we show direct observational evidence that aerosol emissions from the boreal forest biosphere influence warm cloud microphysics and cloud-aerosol interactions in a scale-dependent and highly dynamic manner. Analyses of in-situ and ground-based remote sensing observations from the SMEAR II station in Finland, conducted over eight months in 2014, reveal significant increases in aerosol load over the forest one to three days after aerosol-poor marine air enters the forest environment.We find that these changes are consistent with secondary organic aerosol formation and, together with water vapor emissions from evapotranspiration, are associated with changes in the radiative properties of warm, low-level clouds. The feedbacks between boreal forest emissions and aerosol-cloud interactions and the highly dynamic nature of these Petäjä et al. (2021) Influence of biogenic emissions from boreal forests on aerosol-cloud-interactions, Nature Geosci. (accepted)

Quiet New Particle Formation in the Atmosphere

“…Ratio in Maximum are known to give an important contribution to NPF and subsequent growth of newly formed particles (e.g. Lehtipalo et al, 2018;Petäjä et al, 2022). The corresponding differences were the lowest in the Budapest city center, the site with the largest influence of anthropogenic pollution of the four sites considered here (Salma et al, 2017).…”

Enhanced Nighttime Fog and Low Stratus Occurrence Over the Landes Forest, France

“…High loadings of natural aerosols from late spring to early fall have been found for boreal forests (Tunved et al., 2006). It has been shown that secondary organic aerosol emissions together with evapotranspiration over forests can lead to an increase of liquid water path and cloud droplet number concentration in low‐level liquid clouds (Petäjä et al., 2022). This could also be a potential pathway in the Landes forest, where BVOC emissions have been measured in summer (Kammer et al., 2018).…”

Escalating wildfires in Siberia driven by multiple climate feedbacks under a warming Arctic

“…In the high latitudes, the climatic feedback of wildfire smoke is particularly complex. Fire-emitted carbonaceous aerosols not only perturb the radiation balance 27 , but also modify cloud properties and deposit on the glacier surface 28 , leading to a longer dry season and providing greater opportunities and frequency for extremely large fires. Thus, the complex feedbacks and interactions between fire and climate are big challenges that we face in understanding and managing wildfires.…”

“…Quantitatively, smoke aerosols would induce a decline of almost 8% in summertime rainfall over central Siberia. Such a prominent precipitation suppression is due mainly to the CCN-limited cloud-aerosol regime and fire-smoke aerosol accumulation 27,46 .…”