| 30 Sep 2026
Satellite-based constraints on temperature-dependent aerosol–cloud feedback over a clean boreal forest and a rural continental site
Abstract. Temperature-dependent biogenic aerosol formation has been proposed as a negative climate feedback mechanism. However, the indirect cloud-albedo radiative feedback remains difficult to quantify from observations because in situ observations from clouds are sparse and satellite-derived cloud properties are sensitive to retrieval assumptions, cloud regime, and meteorology. In our attempt to tackle this issue, we combine multiyear field observations with carefully sampled satellite retrievals for two diverse locations: a boreal forest site, Hyytiälä in Finland, and a continental site, Southern Great Plains in USA. We focus on low-level liquid clouds and evaluate the impact of sampling criteria (general cloud-quality filters, a local quality filter, and an adiabatic-consistency criterion) and different fitting methods on the estimation of the temperature-dependent radiative effects of biogenic aerosols. We found that if the adiabaticity requirement is not used, the indirect radiative effects are likely underestimated because non-ideal cloud scenes dilute the observed aerosol-cloud response. Based on carefully selected data sets, we estimate that the clear-sky direct radiative feedback caused by biogenic aerosols is approximately -0.6 Wm−2 °C−1 in a clean environment and about half of that (-0.3 Wm−2 °C−1) in a rural region. The indirect radiative feedback of these aerosols is in the same range with the direct radiative feedback (-0.6 Wm−2 °C−1) in the clean region but it is almost three times stronger (-0.8 Wm−2 °C−1) in the rural region. However, the quantification of the temperature-dependent aerosol–cloud feedback is more straightforward in clean environments than in rural ones, where other emissions can drive the aerosol load and number.
Competing interests: At least one of the (co-)authors is a member of the editorial board of Atmospheric Chemistry and Physics.
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