Cloud Para meter Characteristics of Three Strengthening Convective Systems During Downhill Processes in Beijing

Based on FY-4A geostationary satellite multi-channel data, mesoscale convective systems（MCSs） during three downhill processes of convection strengthening（1 July 2021, 12 June 2022 and 4 August 2022） in Beijing are identified by temperature threshold method. Precipitation data from Beijing-TianjinHebei automatic weather stations, along with data from CMA-BJ mesoscale numerical model, are also utilized to analyze cloud characteristics of MCSs in formation and mature stages. Results indicate that the area of the convective cloud increases slowly, but the brightness temperature gradient is high, the brightness temperature decreases rapidly, the lowest temperature is below-65 ℃ and the maximum temperature variation rate in the area is-40 ℃·（15 min）-1 in the formation stage of MCSs. The maximum bright temperature gradient area corresponds to the inflow and water vapor convergence area, and it is located on the side of the cloud movement direction. In the mature stage, the area of the convective cloud increases rapi