Large-Eddy Simulations of the Isotopic Signatures of Arctic Mixed-Phase Stratocumulus Clouds Under Different Surface and Atmospheric Conditions

Mixed-phase stratocumulus clouds in the polar region affect high-latitude climate in many ways, not least by regulating the boundary layer moisture and energy budgets. Sea ice coverage and thickness are decreasing sharply under global warming, changing the characteristics of the surface underlying much of the polar boundary layer, and the circulation patterns that govern lower tropospheric temperature and humidity inversions may change as well. Given the strength of ocean-ice-atmosphere interactions in the polar boundary layer, it is imperative to understand how different surface and atmospheric inversion conditions affect cloud formation and characteristics from both microphysical and macrophysical perspectives. Stable water isotopes have excellent potential as a tool to study the water cycle in the polar boundary layer, but their applications to understanding mixed-phase clouds in the polar region are limited by the lack of both direct observations and isotope-enabled models at appropriate spatial and temporal scales. Recent observational campaigns such as MOSAiC have observed isotopic composition at and near the Arctic surface under a range of different conditions, creating opportunities to expand the use of isotopes in Arctic water cycle research. Previous research has also established the ability of large-eddy simulations (LESs) to explicitly resolve boundary layer processes in the Arctic region and simulate the sensitivity of Arctic clouds to different atmospheric and surface conditions. To better exploit the potential of recent isotopic observations, we have developed an isotope-enabled large eddy model based on the PyCLES (Python Cloud Large Eddy Simulation) model framework to close some of the gaps between observations and modeling in the study of polar boundary layer clouds. iPyCLES is equipped with a two-moment microphysics scheme and includes representations of all essential isotopic fractionation processes at the surface and within clouds. In this presentation, we briefly introduce a series of sensitivity experiments targeting different surface and tropospheric inversion conditions to evaluate the isotopic signatures of surface-ice-atmosphere interactions within the polar boundary layer. The simulations are based on two well-studied field campaigns conducted near Barrow, Alaska, one in spring and one in autumn. Together with standard metrics of cloud evolution and turbulence mixing, isotope ratios in water vapor, cloud liquid and ice, and snow are tracked during the simulation. Isotopic signatures of each experiment are evaluated for their potential to provide observable constraints on polar clouds and boundary layer processes.