Abstract
The Tropical Rainfall Measuring Mission (TRMM) satellite and a dropsonde-equipped aircraft made simultaneous observations of a cloud cluster (CC) over the East China Sea. Hourly GMS equivalent blackbody temperature (TBB) showed that the CC was in the dissipating stage. The structure of the CC was analyzed using TRMM, dropsonde and rawinsonde data. The cloud top of the CC was an anvil composed of a dense area and a thin area. The precipitation within the cloud area of the CC (defined by TBB < -30°C) was stratiform, and corresponded to the dense anvil area of the CC. The thin anvil area extended to the outside of an apparent CC cloud area. The CC had a multi-layer structure, and shallow convection developed below the thin anvil in the convectively unstable lower troposphere with low-level convergence. The echo top of the shallow convection was less than 4 km (630 hPa). The shallow convection generated an outflow from its upper part. The outflow blew into the area of negative pressure anomaly below the dense anvil at levels of 650 hPa and 750 hPa. Meanwhile, a southeasterly dry wind blew into the stratiform precipitation area of the CC at levels between 700 hPa and 850 hPa. The dry inflow was cooled by evaporation within the precipitation of the CC, resulting in the formation of the negative potential temperature anomaly. Evaporation cooling occurred in the stratiform precipitation region; however, the negative potential temperature anomaly did not reach the surface. It is inferred that the evaporation cooling was not important to the initiation of the shallow convection, although it affected the structure of the CC.
