A Framework to Attribute Tropical Multiscale Precipitation Extremes to Rain Event Morphology in Deep Convective Systems

Abstract

The different spatiotemporal scales used to calculate extreme precipitation intensities can lead to diverging interpretation when investigating their physical origin, impacts, and sensitivity to climate. Besides, the contribution of mesoscale convective systems (MCSs) to tropical precipitation extremes remains loosely quantified on various scales, in particular on kilometer scales. Here, we construct a framework to analyze the cooccurrence of extreme precipitation at km-scale and 1° × 1 day scale to compare their properties in terms of precipitation morphology and regional predominance. Using a storm-tracking algorithm, we contrast the occurrence and precipitation statistics for two types of convective systems across 10 global storm-resolving models and one geostationary satellite product. We do not find a large statistical dependence between rain extremes on these two scales, and they occur in distinct regions. Heavy km-scale events occur mostly over continents and 40% of them are produced by MCSs in observations. Their intensity is independent from the area of rain features. Conversely, heavy 1° × 1 day rain intensities are dependent on the area of rain features, and occur more frequently over oceans, and a third of these events are produced by MCSs. Overall, the transition from deep to MCSs connect extremes across both scales. Compared to observations, models consistently underestimate the precipitating surface and show large discrepancies in the contribution of convective systems to precipitation extremes at each scale. This diagnostic is a key criterion for evaluating the ability of global storm-resolving models to represent how individual convective systems produce realistic heavy rain distributions.