Strong Diurnal Pulsing of Cold Clouds in Rapidly Intensifying Tropical Cyclones

The radially outward propagating diurnal signal in the upper-level clouds (diurnal pulse) is a prominent cyclical feature of tropical cyclones (TCs). This study examines relationships between pulses and TC intensity changes using satellite Infrared data from 2001 to 2018. occurrence duration 24 hr prior or during change are strongly correlated with intensification rate. Rapidly intensifying (RI) TCs have markedly higher frequency (60%–80%) very long-duration pulse (15 hr) significantly longer mean than steady-state (40%–50%) gradually (50%–60%). Long-duration infrequent weakening (20%–30%). Diurnal highly initial cloud-top cooling rate cold-cloud fraction inner core, but less related intensity. In short, strong pulsing cold an evident signature RI TCs.