摘要:利用高频次FY-4A数据资料，研究了四川盆地2018年中尺度对流复合体MCC（mesoscale convective complex）初生和成熟阶段的卫星云图特征。结果表明，MCC对流云团面积在初生阶段和成熟阶段分别以0～50 pixels (15 min)?1和150～200 pixels (15 min)?1的速率增长，最强可达7000～10000 pixels左右。亮温梯度大值区位于初生阶段的低空入流区一侧，集中在云顶纹理最为丰富的240 K等值线附近，最大值为30°C～40°C，基本消失于成熟阶段。云顶红外IR1（infrared radiation 1 channel）和水汽通道IR3（water vapor channel）最低亮温值在初生和成熟阶段变化趋势一致，均为初生阶段迅速下降至190 K左右的最低谷，而成熟阶段维持最低值基本无变化。初生和成熟阶段的IR1和IR3降温率R（cloud top cooling rate）分布形态相似，初始阶段低空入流区一侧的240 K等值线附近的降温率达?40 K (15 min)?1，为显著降温区，成熟阶段的降温幅度普遍升至?25～?10 K (15 min)?1。MCC主体云区初生和成熟阶段的亮温差正负值区分界线基本与221 K等值线重合，最大值分别为6～10 K和0–6 K，且初始阶段低层入流区的降温最为剧烈，达15～20 K (15 min)?1之多，而成熟阶段基本无变化。
关键词:中尺度对流辐合体/
初生阶段/
成熟阶段/
FY-4A/
亮温差
Abstract: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.
Key words:MCC (mesoscale convective complex)/
Convective initiation/
Mature stage/
FY-4A/
brightness temperature difference
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