Modelling and parameterization of lead generated turbulence in the atmospheric boundary layer over Antarctic sea ice

在这个项目中，我们研究了南极海冰上的通道（开放或薄冰覆盖的通道）上的湍流大气过程。特别是在冬季，海冰覆盖的这种不均匀性会产生大气对流，并产生强烈的湍流涡流，影响大气边界层过程和引线下游的气冰相互作用。由于这些过程的尺度非常小，它们必须在最先进的气候模式中被参数化。尽管近年来在高分辨率模拟和参数化方面取得了一些进展，但为了全面了解引线对大气边界层湍流的影响，并为气候和天气预报模式提供可靠的参数化，仍有许多问题需要解决。这些问题涉及诸如气象强迫、铅的几何形状、海冰地形以及铅上形成的小规模有组织对流的影响。该项目分为三个部分，每个部分都有具体的目标。第一个目标是更好地理解导线上的对流过程。为此，我们使用最先进的大涡模拟（LES），对引线附近的大气对流过程进行接近现实的建模。例如，我们考虑铅的几何形状的影响和强迫参数对大气湍流的作用，以及铅上对流羽流与封盖反转的相互作用及其对垂直夹带的影响。这是第一次有可能根据最近一次飞机战役获得的观测数据来验证这种LES运行。第二个目标是在LES结果的基础上改进导线上湍流的参数化，首先用于微尺度大气非涡分辨模式，最后用于气候模式。建模（LES和微尺度）和参数化工作将基于申请人以前的成功合作。新工作的目标是更复杂的情况和气候模式的参数化。估计引线影响的困难之一在于很难从卫星上观察引线。因此，基于高、中分辨率卫星传感器的遥感将支持建模和参数化工作（第三个目标）。该项目侧重于线索和小规模过程，有助于实现SPP 1158总体目标2.2.4，该目标旨在将重点放在对极地地区特别重要的局部影响上，例如冰裂湖和线索对低层大气特征的影响。我们申请资助两名博士研究生，为期3年，一名用于目标(1)的研究，一名用于目标(2)的研究。资助汉堡大学的学生助理（2年）支持目标(3)中提到的遥感工作也是必要的。

In this project we investigate turbulent atmospheric processes over leads (channels either open or with thin ice cover) in Antarctic sea ice. Especially during winter such inhomogeneities in the sea ice cover generate atmospheric convection with strong turbulent eddies influencing atmospheric boundary layer processes and air ice interaction on the downstream side of leads. Due to the very small scales of these processes they have to be parameterized in state-of-the-art climate models. Although some progress has been achieved in recent years with both high resolution modeling and parameterization many questions need still to be solved to understand the impact of leads on atmospheric boundary layer turbulence in all aspects and to arrive at reliable parameterizations for climate and weather prediction models. These questions concern e.g. the impact of meteorological forcing, of lead geometry, of the sea ice topography, and of small scale organized convection developing over leads. The project is divided into three parts with specific goals. The first goal is to obtain a better understanding of convection processes over leads. To that aim we use state-of-the-art large eddy simulation (LES) for a close-to-reality modeling of atmospheric convection processes over and in the close environment of leads. We consider, for example, the impact of lead geometry and the role of forcing parameters on atmospheric turbulence, and the interaction of the convective plumes over leads with the capping inversion and its impact on vertical entrainment. For the first time a validation of such LES runs is possible on the basis of observed data recently obtained by an aircraft campaign. The second goal is to improve parameterizations of turbulence over leads based on the LES results first for microscale atmospheric non-eddy-resolving models and finally for climate models. Both the modeling (LES and microscale) and parameterization work will be based on previous successful cooperation of the applicants. The new work aims at more complex cases and towards the parameterization in climate models. One of the difficulties for an estimation of the lead impact consists in the difficulties to observe leads from satellite. Thus the modeling and parameterization work will be supported by remote sensing based on high and medium resolution satellite sensors (third goal). With its focus on leads and small scale processes this project contributes to the overarching goal 2.2.4 of the SPP 1158 which intends e.g., to put a strong focus on local impacts particularly important in the polar regions such as the influence of polynyas and leads on the characteristics of the lower atmosphere. We apply for the funding of two PhD students for 3 years, one for the work addressed by goal (1) and one for goal (2). Funding is also necessary for student assistants at University Hamburg (2 years) supporting the remote sensing work addressed in goal (3).