Atmospheric River Modeling: Forecasts, Climate Simulations, and Climate Projections

Research in recent years has highlighted the significance of ARs to the occurrence and modulation of weather and hydrology extremes, as well as the critical role they play in helping establish the Earth’s climate—namely its water and energy budgets—through their decisive effect on the poleward transport of water vapor. With this in mind, it is imperative that ARs—and their associated dynamics, thermodynamics, and hydrodynamics—be accurately represented in our weather and climate models. This chapter reviews modeling and model-evaluation studies of ARs, including both weather forecast and climate simulation/projection applications. Specifically, research performed to date on predictive aspects of ARs for short- to extended-range (i.e., 1- to 15-day) weather forecasts is discussed and summarized. In addition, this chapter reviews research and model-evaluation studies that examine and quantify regional and global climate model representations of ARs. By extension, the more the fidelity and systematic biases in climate models are understood and quantified, the more the uncertainty in climate model projection of ARs can be characterized. Thus, this chapter also reviews the research that has examined contemporary sets of climate projections to quantify how ARs and related fields are expected to change. Finally, this chapter summarizes gaps in understanding and research of AR simulations, multi-time-scale forecasting, and climate projections.