The problem of predicting climate change and its consequences is motivated by the increasingly urgent need to adapt to near term trends in climate change and the potential changes in the frequency and intensity of extreme events. This project develops the scientific framework to ascertain the benefit of employing very-high-resolution global models to investigate regional-scale phenomena.
The goal is to test the hypothesis that higher resolution models are necessary to accomplish the related objectives of:
- The explicit simulation of nonlinear phenomena and interactions on the small scale that have feedbacks on large scale climate features; and
- The accurate and explicit simulation of local to regional scale phenomena, including low-probability, high-impact hydrological events.
A rigorous evaluation of this hypothesis with high-resolution simulations of observed climate and variability is the focus. A series of stand-alone component and ensemble coupled present-day climate simulations are used to perform comparisons of high- and low-resolution model configurations to determine the potential advantages of high resolution simulations. Investigation is made for the role of air-sea interaction, the quality of the basic state, and resolution sensitivity on a hierarchy of modes of variability, including the distribution and evolution of extreme events in control, historical, and time-slice experiments of future climate change. An integral component of this project is the development of new objective diagnostics and metrics to gauge the potential benefit of employing high resolution to improve their representation of regional scale phenomena, especially those related to the hydrological cycle. The pathway to the goals requires an improved understanding of critical sensitivities in model formulation that have been indentified from preliminary very-high resolution coupled simulations. The experimental protocol will enable investigation of these sensitivities, which include the interaction of physics with the choice of dynamical core of the atmospheric model and the initialization of the ocean model, both of which contribute to the development of model biases compared to observations. Implicit in this pathway toward developing a more realistic very-high resolution coupled model for regional projections of climate change is the exploration of the benefit of very-high resolution contributed by the atmospheric and ocean models, respectively.