The exceptionally low temperature in the tropical tropopause layer (TTL) restricts the amount of water vapor entering the stratosphere. However, moisture may also enter the stratosphere in its frozen state, and the amount thereof depends on hydrometeor sedimentation and air vertical velocity. We investigate the sensitivity of frozen hydrometeor transport pathways to substantial perturbations of the TTL temperature structure in global storm-resolving model simulations. A special focus is laid on the question which process—convection, slow upwelling within the background velocity field, in-cloud radiative processes, gravity waves or turbulence—is responsible for most of the transport. The study shows that the main contribution to the frozen hydrometeor flux is cold-point overshooting convection in both the control and perturbed scenario. The average convective event transports an increased amount of frozen hydrometeors at the cold-point tropopause, when the later is warmed. This finding can be explained by scaling of frozen moisture content with Clausius Clapeyron in a saturated environment.

中文翻译：

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平流层气溶胶加热对热带对流层顶层冰冻水凝物输送路径的影响

热带对流层顶层（TTL）的极低温度限制了进入平流层的水蒸气量。然而，水分也可能以冻结状态进入平流层，其数量取决于水汽沉降和空气垂直速度。我们研究了全球风暴解析模型模拟中冰冻水凝物传输路径对 TTL 温度结构显着扰动的敏感性。特别关注的问题是哪个过程（对流、背景速度场内的缓慢上升流、云内辐射过程、重力波或湍流）负责大部分传输。研究表明，在控制和扰动情况下，对冻结水凝物通量的主要贡献是冷点超调对流。当对流层顶变暖时，平均对流事件会在冷点对流层顶输送更多数量的冰冻水凝物。这一发现可以通过在饱和环境中用克劳修斯·克拉佩龙（Clausius Clapeyron）对冷冻水分含量进行缩放来解释。