Formation and Evolution of Pileus Cloud Near the Tropopause

薄层卷云广泛分布于14至18公里高度的对流层顶过渡层（TTL）。它们在气候、平流层湿度和遥感方面的作用最近引起了相当大的关注。然而，由于云层非常脆弱，高度很高，它们的起源仍然很大程度上不确定。这项研究探索了一种假设，即一些TTL卷云起源于毛状云——在强烈对流抬升之前形成的薄层凝结物——随后演变覆盖热带的大片地区。看来，至少在其初始阶段，菌毛演化的问题本质上是确定大气深层对流如何在分层TTL中强迫运动的问题。采用大涡模拟云解析模型，研究了对流与环境相互作用形成羽状云的三种主要情景。这项研究的广泛影响来自对流层顶过渡层卷云在气候和控制平流层湿度方面的重要作用。此外，该奖学金还资助了一名女研究生。

Thin layers of cirrus are widespread in the tropopause transition layer (TTL) between 14 and 18 km altitude. They have attracted considerable recent attention for their role in climate, stratospheric humidity, and remote sensing. However, because the clouds are very tenuous and very high, their origins remain largely uncertain. This study explores a hypothesis that some TTL cirrus originates as pileus cloud - thin stratiform layers of condensate that form ahead of vigorous convective uplift - that subsequently evolve to cover large areas of the tropics. It appears that, at least in its initial stages, the problem of pileus evolution is essentially one of determining how atmospheric deep convection forces motions in the stratified TTL. A large-eddy-simulation cloud resolving model is used to investigate three main scenarios of the how convection interacts with its environment to form pileus clouds.The broader impacts of this study are derived from the important roles that tropopause transition layer cirrus have in climate and in controlling stratospheric humidity. Moreover, this grant supports one female graduate student.