Diurnal Propagation of Precipitation in Landfalling Tropical Cyclones

Abstract While diurnal pulses (outward propagation) of clouds and precipitation in tropical cyclones (TCs) over the ocean have been well recognized, the diurnal propagation of precipitation (DPP) in landfalling TCs and its impacts on overland precipitation are less known. To fill this gap, this study utilizes the 30‐min Integrated Multi‐satellite Retrievals for GPM (IMERG) data set to identify overland DPP events in landfalling TCs. Overall, overland DPP events account for approximately 30% of all landfalling TC days globally. In these overland DPP events, a positive precipitation anomaly is observed to propagate radially outward from the inner‐core to the outer‐rainband region of TCs, with enhanced precipitation occurring along the propagation path. The propagation signal in overland DPP events initiates later (06–09 LST) than open‐ocean DPP events, which typically initiate at 03–06 LST. This difference is attributed to the presence of two distinct initiation times for the overland DPP signal: early morning (00–06 LST) and near noon (09–15 LST). The early morning initiation is primarily driven by convection‐induced inertial gravity waves, which result from the nocturnal long‐wave radiative cooling enhancement of inner‐core convection in strong TCs. In contrast, overland DPPs initiated near noon are typically produced by weak TCs where the inner‐core convection peaks at noon in response to the short‐wave radiative heating. As a result, TCs during overland DPP events tend to produce wider rainfall distribution and more extreme rainfall, even in landfalling weak TCs.