Understanding clouds and precipitation at the sub kilometer scale using HALO and ICON – Air masstransformations in the Arctic (UCP-Arctic)

众所周知，北极气团的演变对云和降水的形成和持续很重要。有两种现象-从南方侵入北极的暖湿气流和从北方爆发的干冷空气-正在造成特别强烈和迅速的气团变化。在这些事件期间，例如，云量、稳定度和水分收支在空间和时间上的变化。由于这些快速的变化和北极条件非常低，往往是强烈的逆温，全球模式与相当粗糙的分辨率有困难，以代表这些过程。为了更好地理解并更好地表示关键过程，HALO飞机的详细观测和ICON-LEM的高分辨率模拟将在该项目中应用。由于HALO飞机的航程很远，因此可以多次测量同一事件，从而对气团结构有广泛的了解。将采用拉格朗日飞行策略，以捕获感兴趣的事件期间特定空气质量的时间演变。这些飞行将得到ICON-LEM模拟的补充，这些模拟具有沿着飞行路径（1公里至100米）的局部精确分辨率。这种独特的空中观测和高分辨率建模的组合将被用来估计在所观察到的潮湿入侵和冷空气爆发的水分预算。水分收支产品，然后将被用来调查这些变化过程中的降水效率和它对北极混合相云的持久性的影响等公开的问题。虽然拉格朗日飞行策略将支持科学问题，并允许新的和独特的研究，但它对飞行规划带来了巨大的挑战，因为必须事先估计和跟踪气团的运动。因此，该项目还将通过进行高分辨率预报来支持飞行规划，并将其用于跟踪特定的气团。应用轨迹集合还将有助于估计剩余的不确定性，以便对有用的飞行模式作出合理的估计。结合空中观测和高分辨率模拟，将导致更好地了解湿入侵和冷空气爆发期间的水分收支和混合相云的持续性的变化。

The evolution of arctic air masses is known to be important for the formation and persistence of clouds and precipitation. Two phenomena -- the warm moist intrusions from the south into the Arctic and the cold dry air outbreaks from the north -- are causing especially strong and fast changes in the air masses. During these events, the states of e.g., cloudiness, stability, and moisture budget change in space and time. Due to these fast changes and the arctic conditions with very low and often strong inversions, global models with a rather coarse resolution have difficulties to represent these processes. To create a better understanding and with that a better representation of the key processes, a combination of the detailed observations from the HALO aircraft and high-resolution simulations with the ICON-LEM will be applied within this project. Due to the long range of the HALO aircraft, it will be possible to measure the same event several times and thus gain a broad insight into the structure of the air mass. A Lagrangian flight strategy will be pursued to capture the temporal evolution of specific air masses during interesting events. The flights will be complemented by ICON-LEM simulations with locally refined resolutions along the flight path (between 1 km and 100 m). This unique combination of airborne observations and high resolution modelling will be used to estimate the moisture budget during the observed moist intrusions and cold air outbreaks. The moisture budget product will then be used to investigate the open questions like the precipitation efficiency during these changes and its influence on the persistence of arctic mixed-phase clouds. While the Lagrangian flight strategy will support the scientific questions and allow new and unique research, it causes huge challenges for the flight planning, as the movement of the air masses have to be estimated and tracked beforehand. This project will therefore also support the flight planning by performing high-resolution forecast and use these for the tracking of specific air masses. The application of an ensemble of trajectories will also help to estimate the remaining uncertainties to provide a reasonable estimate for useful flight patterns. Combining airborne observations and high resolution modelling will lead to a better understanding of the changes of the moisture budget and the persistence of mixed-phase clouds during the moist intrusions and cold air outbreaks.