资源环境科技发展态势分析平台

Upper-tropospheric clouds in the outflow layer of typhoons can affect the track of typhoons (tropical cyclones) through radiation effects. In this study, the microstructure of the outflow-layer clouds of several typhoons was examined. Cloud radar observations of three typhoons around Japan revealed numerous protuberances in echoes along the base of the upper-level clouds, which are referred to as mammatus-like echoes. The horizontal and vertical scales of these mammatus-like echoes were 0.5–3.0 km and 0.3–1.5 km, respectively. Vertical observations revealed downward (upward) Doppler velocities in (between) the hanging echo regions. Upward and downward velocity maxima were estimated at 3 m s⁻¹ around the mammatus-like echoes. Neutral stratification developed in the dry layer beneath the cloud base in which the mammatus-like echoes formed. These mammatus-like structures may promote mixing along the cloud base that contributes to dissipation of the outflow-layer clouds.