More Weather or More Water: What is Driving Increases in Extreme Precipitation?

Abstract:

A climatic shift in the frequency and intensity of extreme precipitation events can be attributed to some combination of associated change in the moisture content of the atmosphere and/or the dynamic forcing that drives extreme events. This study examines the latter, by developing an objective method for determining the primary driver of a particular event (frontal passage, extratropical cyclone, tropical cyclone, or North American monsoon) and employing that method to quantify the frequency with which each of these types of event occur.

Using over 3,000 long-term daily precipitation records from the continental United States, the annual frequencies of extreme precipitation events associated with fronts and extratropical cyclones are compared against the overall occurrence of those causes, in an attempt to determine the strength of the relationship between a change in frequency of a certain meteorological driver, and the frequency with which it results in an extreme precipitation event. Results are presented by season and region within the United States.

We know that extreme events are happening more often. Is that because of more moisture, or a more active environment?