Temperature and CAPE dependence of rainfall extremes in the eastern United States

We analyze how extreme rainfall intensities in the Eastern United States depend on temperature T, dew point temperature T-d, and convective available potential energy CAPE, in addition to geographic sub-region, season, and averaging duration. When using data for the entire year, rainfall intensity has a quasi Clausius-Clapeyron (CC) dependence on T, with super-CC slope in a limited temperature range and a maximum around 25 degrees C. While general, these features vary with averaging duration, season, the quantile of rainfall intensity, and to some extent geographic sub-region. By using T-d and CAPE as regressors, we separate the effects of temperature on rainfall extremes via increased atmospheric water content and via enhanced atmospheric convection. The two contributions have comparable magnitudes, pointing at the need to consider both T-d and atmospheric stability parameters when assessing the impact of climate change on rainfall extremes.