Recent composite analysis of landfalling tropical cyclones (TCs) suggests a rain rate peak in the early morning, which contradicts the typically observed peak in convective precipitation over land seen in the late afternoon to early evening. We conducted a set of idealized simulations of TCs and analyzed observational data from TC Bebinca (2018), which stalled near the shoreline of southern China. We show a distinct land–sea contrast in the diurnal variation of TC precipitation and an 8–12 hr offset between the peak precipitation time over land compared with that over the sea in a TC that stalls at the shoreline. The highest land surface temperature and maximum low‐level buoyancy during the afternoon led to peak precipitation over land at this time. However, the peak precipitation over the sea in the early morning was generated by the increase in relative humidity caused by nighttime radiative cooling and enhanced instability. Plain Language Summary Heavy rainfall associated with tropical cyclones (TCs) causes great economic loss and fatalities in coastal and inland regions worldwide. Do TCs show predictable diurnal fluctuations in rainfall, which can be valuable information for TC flooding risk or water resource management? The diurnal cycle in TC cloudiness over oceans might provide clues to this problem. Recent studies suggest an early morning peak in TC rainfall over land and sea, which seems to contradict the late afternoon to early evening peak observed over land for shower and thunderstorm activity unrelated to TCs. We found that for a TC stalled at the shoreline, peak rainfall over land lags that over sea by 8–12 hr, although the peak rainfall over sea still occurs in the early morning. Our results show, that for a landfalling TC, the offset in peak rainfall time between land and sea stems from the influence of land–sea thermal and roughness contrasts on the atmosphere.
展开▼
