A Comparison of Aerosol-Cloud Microphysical Effects from Long-Range Transported Aerosols in Two Different Systems: The Arctic Ocean and the Subtropical North Atlantic

Aerosol-cloud interactions are a major uncertainty in climate science, but their importance is poorly constrained due to confounding meteorological factors, confounding direct and semi-direct effects, and complex cloud responses to aerosol type and amount. Nonetheless, given a long time series of observations and the ability to stratify observations by meteorological regime, it is possible to isolate meaningful regional cloud property differences in the presence and absence of long-range transported aerosol. In this presentation, we will compare and contrast aerosol microphysical effects on clouds over two very different areas: the Arctic Ocean and the subtropical North Atlantic. Based on tens of millions of satellite observations and aerosol model simulations, we find that long-range transported aerosols are in some cases associated with very large differences in cloud radiative effects at the surface, but that co-varying meteorological changes on factors such as cloud fraction likely explain much, though not all, of this signal. We will discuss the observed aerosol microphysical effects on cloud fraction, phase, and precipitation frequency found in both systems after normalizing for meteorological regime.