The Meteorology of Extreme Precipitation and Implications for Future Planning (Invited Presentation)

Rising global temperatures from increasing greenhouse gas concentrations will increase overall atmospheric water vapor concentrations. There is a high level of scientific confidence that this will increase the future intensity and frequency of extreme precipitation events, even in regions where overall precipitation may decrease. Design of infrastructure based solely on historical climate records, the current practice, is likely to lead to under-design of runoff control structures, and associated increased flood damages. However, the magnitudes of future changes in extreme precipitation design values are uncertain and probably regionally variable because changes in the meteorological phenomena that cause extreme precipitation will not be regionally uniform. An examination of past precipitation extremes reveals the range of meteorological situations that can cause such events. There has been relatively little comprehensive research on how specific types of meteorological phenomena might change in response to global warming, particularly the subset of such phenomena responsible for extremes. Fronts associated with extratropical cyclones are the single most dominant meteorological feature associated with extreme precipitation. Furthermore, in the northeastern quadrant of the U.S., summer fronts cause most extreme precipitation events. Such relatively weak systems (compared to fronts in other seasons) may pose a special challenge for assessing future changes. This talk will provide an overview of recent research on extreme precipitation trends in the U.S. and the meteorology behind such trends. The implications for future planning of infrastructure that must meet design standards for runoff will be discussed.