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。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气流——正在引起气团特别强烈和迅速的变化。在这些事件中，云量、稳定性和水分收支等状态在空间和时间上都发生了变化。由于这些快速变化和极低且往往很强的逆温的北极条件，具有相当粗分辨率的全球模式难以表示这些过程。为了更好地理解和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飞机的远程飞行，它将有可能对同一事件进行多次测量，从而获得对气团结构的广泛洞察。我们将采用拉格朗日飞行策略来捕捉有趣事件中特定气团的时间演化。这些飞行将由ICON-LEM模拟进行补充，沿着飞行路径（在1公里到100米之间）进行局部精确分辨率的模拟。这种航空观测和高分辨率模拟的独特结合将用于估计观测到的潮湿入侵和冷空气爆发期间的水分预算。然后将利用水分收支产品来研究这些变化过程中的降水效率及其对北极混合相云持续的影响等开放性问题。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，但它给飞行计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，该项目还将通过执行高分辨率预报来支持飞行计划，并将其用于跟踪特定气团。轨迹集合的应用也将有助于估计剩余的不确定性，从而为有用的飞行模式提供合理的估计。将空中观测与高分辨率模拟相结合，将有助于更好地理解湿润侵入和冷空气爆发期间的水分收支变化和混合相云的持续存在。

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.