Aircraft-observed High Supersaturation Indicates the Potential of Aerosol Convective Invigoration Effect

Deep convective clouds (DCCs) drive much of the global circulation and hydrological cycle, especially over the tropics. Aerosols can invigorate the formation and development of DCCs by increasing the condensation efficiency of the water vapor to cloud water. A major pathway for aerosol effects on DCCs is called condensational aerosol convective invigoration. This suggests that adding aerosols to clean clouds at high supersaturation conditions leads to more numerous and smaller droplets. This process reduces supersaturation and releases latent heat, invigorating the updrafts. However, high supersaturation, a prerequisite for the invigoration, has been simulated but not observed. Here, based on aircraft observations of the Cloud, Aerosol, and Monsoon Processes Philippines Experiment from August to October 2019, supersaturation values reaching up to 10% were observed in tropical DCCs at the supercooled zone below 0°C. The supersaturation increased with height and with the progression of coalescence and accelerated updrafts, peaking over the −10°C to −20°C isotherm range. Additionally, an increase in the number of small cloud droplets was associated with a decrease in supersaturation. These observations support the potential for condensational aerosol convective invigoration.