An investigation into microphysical processes of autumn frontal clouds influenced by the warm conveyor belt in Central China

Abstract

Understanding frontal clouds and precipitation is crucial due to its increasing variability and intensity driven by global warming, which impacts agriculture, water resource management, and climate adaptation. Autumn precipitation in Central China is frequently induced by extratropical cyclones, often featuring a frontal cloud system influenced by warm conveyor belt (WCB). In this paper, the detailed microphysical processes of an autumn precipitation event were examined using reconstructed vertical profiles of polarimetric variables, supplemented with numerical simulation to better depict the microphysics evolution in different stages. Results showed that during the initial stage, a strong, inclined updraft and supersaturated layer influenced by WCB, enhanced the formation and depositional growth of ice particles above −10 °C level, then ice particles grew by riming in addition to aggregation in −5–0 °C layer while precipitation particles coalescence and collecting cloud droplets occurred in warm cloud. As the vertical extent of supersaturated layer increased, the intensified process of collecting cloud droplets and vigorous riming process contributed to the maximum surface rainfall intensity. In the weakening stage, ice-phase processes attenuated before the warm cloud processes showed reducing tendencies. This decline is attributed to weakened inclined updraft and supersaturated layer falling below 0 °C level, which impaired the conditions necessary for ice-phase processes. It is concluded that the thermodynamic structure of WCB, namely the vertical extension of inclined updraft and the presence of supersaturated layer, significantly influenced both the ice-phase and liquid-phase microphysical processes of the frontal cloud system as well as the surface precipitation.