Fine-Scale Turbulence, Cloud Microphysics, and Radiative Cooling Rate Measurements in the Entrainment Interface Layer of Marine Stratocumulus

虽然对层积云的混合和辐射过程的一般认识已经取得了很大进展，但层积云的反馈过程的表示在气候预估中造成了很大的不确定性。这些不确定性部分是由于在理解和实际描述主要在云顶的精细尺度混合方面存在问题。云顶冷却（夹带、辐射和蒸发冷却）与动态/湍流过程密切相关。云顶冷却导致浮力减少，从而引起云内的垂直运动。垂直运动随后产生湍流，增加了夹带过程和相关的蒸发冷却。为了研究这些过程，我们提出了以下项目目标：(a)提高对夹带界面层（EIL）精细尺度结构的理解，(b)量化EIL对Sc云夹带的影响，以及(c)评估辐射加热和冷却速率在云夹带和对流过程中的作用。为了达到这些目标，将在亚速尔群岛进行观测活动，使用已建立的直升机机载组合传感器包ACTOS（机载云湍流观测系统）和SMART- HELIOS（光谱模块化机载辐射测量系统）的改进版本进行观测。两种仪器平台作为外部货物由一架直升飞机以低真空速携带。独特的传感器包能够以高空间分辨率（主要在分米范围内）对动态、热力学、云微物理和辐射参数进行原位测量。世界上没有其他测量平台可以达到如此高的分辨率，然而，这对于实现本建议的总体目标至关重要。考虑到EIL的厚度可以小到10米，这一点尤其正确，因此，高测量分辨率至关重要。

Although much progress has been achieved in the general understanding ofmixing and radiative processes of Stratocumulus (Sc), the representation of feedback processes of Sc clouds causes significant uncertains in climate projections. These uncertainties are partly caused by problems in understanding and realistically describing fine-scale mixing mainly at cloud top. Cloud top cooling (entrainment, radiative and evaporative cooling) and dynamic/turbulent processes are strongly linked. Cloud top cooling results in a buoyancy reduction which induces vertical motion within the clouds. Vertical motion subsequently generates turbulence that increases entrainment processes and associated evaporative cooling. In order to investigate these processes we suggest the following project objectives: (a) to improve the understanding of the fine-scale structure of the entrainment interface layer (EIL), (b) to quantify the influence of the EIL on the entrainment in Sc clouds, and (c) to evaluate the role of radiative heating and cooling rates in cloud entrainment and convection processes. In order to reach these goals observations with a modified version of the established, helicopter--borne, combined sensor package ACTOS (Airborne Cloud Turbulence Observation System) and SMART--HELIOS (Spectral Modular Airborne Radiation measurement sysTem) will be performed in an observational campaign at the Azores. Both instrumental platforms are carried as external cargo by a helicopter with low true airspeed.The unique sensor package enables in-situ measurements of dynamic, thermodynamic, cloud microphysical, and radiative parameters with a high spatial resolution (mostly in the decimeter range). No other measurement platform world-wide can achieve such a high resolution which is, however, crucial to achieve the general aims of this proposal. This is particular true considering that the EIL can have thickness as small as 10 m, therefore, high measurement resolution is critical.