Orographic Precipitation Response to Microphysical and Environmental Perturbations for Idealized Moist Nearly Neutral Flow

Orographic precipitation plays a vital role in providing water resources to mountain communities. The precipitation type, amount, and location are determined through complex interactions between cloud microphysics and environmental conditions. Previous studies have explored the sensitivities to these factors through “one-at-a-time” perturbations, where one parameter is perturbed while keeping the rest constant. Although this method does provide information on parameter sensitivity, it is limited, and perhaps misleading, as those experiments are performed with respect to a constant baseline or default for other input factors. This study aims to explore the sensitivity of orographic precipitation to changes in microphysical and environmental parameters using the Morris screening method, which is a robust statistical tool allowing for simultaneous perturbation of numerous parameters. This method is applied for the first time to the study of orographic precipitation. Idealized simulations of quasi-2D moist nearly neutral flow representative of an atmospheric river over a bell-shaped mountain are performed and the controls on surface precipitation and cloud development are analyzed. In addition, results of a variance-based sensitivity analysis will be presented to provide both a qualitative and quantitative investigation of the sensitivity of orographic precipitation to model parameters.