Quantifying precipitation susceptibility over the western North Atlantic Ocean during ACTIVATE

This paper addresses the challenges in quantifying the sensitivity of precipitation to changes in cloud droplet number concentration at fixed liquid water path, i.e., precipitation susceptibility. To provide a better observational constraint, the precipitation susceptibility is computed from an extensive 3-year aerosol and cloud dataset of a recent field campaign over the western North Atlantic Ocean. The key findings are threefold. First, the precipitation susceptibility at 2 km resolution ranges from −0.3 to 0.5 depending on liquid water path, which is much lower than previous observational-based estimates. Second, the dependence of the 2-km precipitation susceptibility on liquid water path does not show a sharp peak, which is incompatible with the classic three-regime pattern. Lastly, the resolution dependence of the precipitation susceptibility calculation can be quantified and understood with a simple statistical framework.