Characteristics of MCC from Convective Initiation to Mature Stage Over the Sichuan Basin Based on FY-4A Satellite Data

The characteristics of the Mesoscale Convective Complex (MCC) from convective initiation to mature stage over the Sichuan Basin in 2018 were analyzed using high-frequency FY-4A satellite data. The results indicated that the area of MCC convective cloud increased at a rate of 0–50 pixels (15 min)⁻¹ at the convective–initiation stage and at 150–200 pixels (15 min)⁻¹ at the mature stage, finally reaching 7, 000–10, 000 pixels. The maximum temperature gradient is located on the side of the low-level inflow zone at the convective–initiation stage, which is concentrated near the 240 K contour with the most abundant texture in the cloud top, having a maximum value of 30°C–40°C. This feature basically disappears at the mature stage. The variation in the minimum infrared radiation 1 channel (IR1) and water vapor channel (IR3) at the convective–initiation and mature stages are consistent; both rapidly decrease to 190 K at the convective–initiation stage, while the minimum value remains unchanged at the mature stage. The distribution patterns of cloud top cooling rate (R) of IR1 and IR3 are also similar. The significant R, which is close to the 240 K on the side of the low-level inflow zone, reaches −40 K (15 min)⁻¹ at the convective–initiation stage but remains stable from −25 to −10 K (15 min)⁻¹ at the mature stage. The maximum brightness temperature difference (D) is 6–10 K at the convective–initiation stage and 0～6 K at the mature stage. Moreover, R(D) in the low-level inflow zone is the most significant at the convective–initiation stage, remaining steady at the mature stage.