A distinct type of heavy rainfall with large raindrops over extratropical regions revealed by 10 years of GPM spaceborne radar measurements
Ryu et al. (2025)
Large raindrops are typically associated with intense continental thunderstorms, where strong convection promotes rapid growth through collision and coalescence. But are large-drop heavy rainfall events limited to these environments?
Using 10 years of observations from the Global Precipitation Measurement (GPM) Dual-frequency Precipitation Radar (DPR), Ryu et al. (2025) revisit this long-standing assumption by examining the global occurrence of heavy rainfall characterized by relatively large raindrops and low drop concentrations. Applying a Gaussian Mixture Model to storm-height observations, the authors identify two distinct types of large-drop heavy rainfall: a high storm height (HSH) type associated with deep convection and a previously underappreciated low storm height (LSH) type occurring in shallower storm systems.
Their findings show that:
- Large-drop heavy rainfall is not confined to deep continental convection. Approximately 38% of identified events belong to the LSH type, which occurs predominantly over midlatitude oceans.
- The HSH and LSH types exhibit similar near-surface drop size characteristics but differ substantially in storm structure and environmental conditions. HSH events are associated with deep convective clouds and warm environments favorable for collision–coalescence growth, whereas LSH events occur in colder environments with lower melting layers.