Role of moist processes in the development of the March 2005 atmospheric river event

Landfalling atmospheric rivers (ARs) are linked to heavy precipitation and extreme flooding, most notably along the western coast of North America. The duration and magnitude of landfalling ARs are correlated to their hydrological impacts on land. The forecast of these hydrologically significant landfalling events can be improved through a better understanding of how they differ from other landfalling events and an investigation of the mechanisms leading to their development prior to landfall. Here, we use the Weather Research and Forecasting (WRF) model to simulate the development of a single, well observed, persistent landfalling AR event at high resolution (4 km) in order to quantify the role of moisture in AR persistence along the coastline. The control simulation compares well against observations, in both the vertical structure and narrow geometry of the AR as it propagates eastward over the basin. We present results from perturbation experiments in which certain feedbacks related to the role of moist processes are in the development of the event are turned off.