More Frequent Intense and Long-Lived Storms Dominate the Trend in Central U.S. Rainfall

The changes in extreme rainfall associated with a warming climate have drawn significant attention in recent years. Mounting evidence shows that sub-daily convective rainfall extremes are increasing faster than the rate of change in the atmospheric precipitable water holding capacity with a warming climate. However, the response of extreme precipitation strongly depends on the type of storm supported by the meteorological environment. Using a long-term high-resolution gridded precipitation dataset along with rain gauge network data and atmospheric reanalyses, this study reveals that changes in the characteristics of Mesoscale Convective Systems (MCSs), the largest type of convective storm, dominate the observed increase in late springtime total and extreme rainfall in the central U.S. More precisely, the increased rainfall is primarily associated with increased intensity and frequency of long-lasting MCSs. These changes are supported by surface warming over the Rockies that increased the pressure gradient across the central U.S. The latter strengthened the climatological southerly low-level jet in the Central/Northern Plains that transports warm air to that region, favoring more intense and longer-lived MCS precipitation.