Trends in Magnitude, Frequency, and Timing of Extreme Rainfall over Short Durations

There is a consensus that the increase in atmospheric moisture-holding capacity, due to the rise in global temperature, is changing the patterns of extreme rainfall events. Convective events, which explain the maxima for short durations, have been found to be more sensitive to changes in temperature. Some even propose that the increases in precipitation will go beyond those explained by the Clausius-Clapeyron relationship.

Many researchers have conducted trend analyses to understand the changes in rainfall magnitude and frequency over existing records, but these studies have been limited to daily and hourly gage data. Using hourly rainfall data does not allow for studying trends for shorter duration extreme events (< 1 hr); also, these fixed, clock data do not provide the true rainfall maxima for short durations (at least up to 3 hrs.).

In this work, we study trends in short-duration rainfall events (15 min to 6 hr.) for gages in and around Tennessee, using 15-min high-resolution data. We propose to look at trends in event magnitude, frequency, and timing. We use an event-based approach, choosing a range of Minimum Inter-storm Times (MITs) to separate independent events. This study will allow us to determine whether the frequency and magnitude of short-duration extreme events are increasing over time and whether extreme events are getting more concentrated in the warm season.