Impact of cloud radiative forcing on tropical cyclone frequency and intensity through tuning the cloud ice-to-snow diameter threshold

Abstract Cloud radiative effect (CRE) is crucial for the development of tropical cyclones (TCs). This study investigates the impact of cloud radiation on TC seeds and TCs in an aquaplanet model by tuning ‘threshold diameter to convert cloud ice particles to snow’ (DCS). With increased cloud cover associated with higher DCS, seed frequency decreases, but the greater intensity increase of seeds leads to a higher survival rate from seeds to TCs. The changes in large-scale circulation within the models are responsible for the reduced seed frequency. Higher DCS enhances equatorial cloud liquid and ice amounts, thereby intensifying radiation heating to the tropics. Increased radiation leads to more moisture and higher temperatures at high levels and increases the temperature gradient from the tropics to the subtropics, thereby intensifying the Hadley circulation. The resulting decrease in convective available potential energy and intensification of vertical wind shear act as inhibiting factors for seed genesis. Besides, the presence of more high-level clouds accumulates both longwave and shortwave heating, creating favorable thermal conditions for the circulation to develop at the mesoscale. This process supports the growth of seeds into mature TCs, resulting in higher survival rates from seeds to TCs. The findings on TCs and CRE in aquaplanet models could serve as a foundation and provide evidence for studies conducted in more complex environmental conditions.