Observational analysis of vertical structure of a heavy precipitation event in Shanghai during Meiyu period in 2020

Using the observations with high temporal and spatial resolution from multiple ground-based remote sensors such as microwave radiometer (MWR),micro rain radar (MRR),wind profiler and millimeter cloud radars,a synergistic analysis was conducted for the features of vertical structure in thermodynamics,dynamics and other aspects of atmospheric characteristics for a heavy precipitation event in Shanghai on 15 June 2020. The main results are as follows. (1) Southwest wind dominates in the middle and lower levels of troposphere before the rainfall occurs,which provides plenty of water vapor for the Shanghai area and results in a significant increase of moisture in this area. High moisture and temperature in low level of the troposphere lead to continuous increase of the atmospheric instability before the rainfall. And the K index calculated based on MWR observations reaches 35℃ and even higher around 10 hours before the rainfall. When the rainfall occurs,temperature drops and moisture decreases in low level. (2) Deep cloud is observed in this event. The cloud layer thickness is generally larger than 12 km and the largest cloud thickness is as large as 14 km. The melting layer is located around height of 4.7 km. (3) Distinguished features of rainy cloud systems can be observed at the different stages of rainfall. The strong echoes of raindrops concentrate below 3 km intermittently at the early stage. The melting layer is stable,and the strong echoes of raindrops occur continuously and extend vertically to over 4 km with raindrop's falling velocity of 6 m·s^-1 at the middle stage. The cloud top reduced to 9 km and the echoes of raindrops get weaker,showing an obvious feature of weak rainfall at the final stage.