Collaborative Research: Global Climate Model Simulations of Extreme Cold-Air Outbreaks

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

This project has two primary objectives. The first is a determination of the capabilities and limitations of global climate models with respect to their simulation of cold wave characteristics. The second is the use of climate models (a) for the diagnosis of the variability of extreme cold outbreaks in terms of dynamical and physical processes and (b) as a basis for projecting future changes in the characteristics (e.g., frequency, intensity, geographical distribution) of cold air outbreaks over the decade-to-century timescale. The research is motivated by the fact that the impacts of changes in the characteristics of extreme events, of which cold outbreaks are prime examples, are likely to be at least as important as associated changes of climatic averages. The project will utilize a suite of state-of-the-art global climate models, including several versions of the National Center for Atmospheric Research's (NCAR) Community Climate System Model, as well as the National Centers for Environmental Prediction (NCEP)/NCAR global reanalysis. The PIs will test several hypotheses: 1). That enhanced resolution permits more successful simulations of the shallow cold outbreaks that sometimes occur over North America; 2). That both dynamic and thermodynamic processes are important and necessary for the penetration of extreme cold-air outbreaks into middle latitudes; 3). That future changes of cold outbreaks under greenhouse forcing will be determined at least as much by changes in the large-scale circulation as by thermodynamic warming. Finally, the research will seek to determine how Eurasian cold outbreaks differ from those in North America, in both present-day and greenhouse simulations. Broader impacts will be achieved through two expected outcomes: (1) improvement in operational medium- and long-range predictability of cold outbreaks based on antecedent pressure and ocean temperature conditions, and (2) the first assessment of the future behavior of cold outbreaks in a greenhouse-forced climate. The ability to anticipate shifts in the frequencies and/or intensities of cold air outbreaks can have large and beneficial impacts on planning and policy. Additional broader impacts will be the incorporation of the research results: into undergraduate teaching at both the University of Illinois and Beloit College; into a second edition of an introductory-level undergraduate textbook; and into a publicly accessible website on extreme cold outbreaks.