Identifying Robust Aerosol-Cloud Relationships in Satellite Observations

When reviewing the literature concerning evidence for interactions between aerosols and liquid clouds in satellite observations, three recurring themes arise that often call into question the robustness of the results: What are the impacts of measurement uncertainties on the results? How can we be sure the aerosols and clouds are really interacting? What is the role of synoptic environment? Focusing on warm clouds, this study employs a large number of complementary satellite and model-derived datasets to explore these questions in detail and distinguish robust aerosol-cloud interactions from transient effects that may be artifacts of the methodology or datasets adopted. The sensitivity of inferred aerosol effects to the source of aerosol information, uncertainties in observed aerosol and cloud properties, local environmental conditions, and the relative vertical placement of cloud and aerosol layers are examined. The analysis uncovers some robust relationships between the properties of liquid clouds and certain aerosol metrics but also suggests that many relationships depend on the specific choice of datasets employed or fail to exceed realistic noise levels imposed by uncertainties in current satellite products. Furthermore, many relationships that are robust in specific regions at certain times of year are not universal globally. These results may have significant implications for how to best represent aerosol-cloud interactions in global models.