The NASA Arctic Radiation-Cloud-Surface-Aerosol-Interaction Experiment (ARCSIX) in the context of current and future Earth Radiation Science missions

ARCSIX is an interdisciplinary aircraft investigation about the role of clouds and radiative processes during the springtime and summer Arctic sea ice melt. NASA will conduct two field campaigns in Greenland from May to August 2024 with three aircraft, which are based at the Pituffik Space Base (formerly known as Thule). Collectively, they will sample the properties of the surface, clouds, and aerosols, primarily from the North Coast of Greenland to the North Pole – a region that is considered the ‘last bastion’ of multi-year sea ice, in contrast to regions where sea ice has already become highly seasonal. The scientific focus is on interaction processes between the cryosphere and the atmosphere as the Arctic is transitioning to a seasonally ice-free state. Of particular interest is the life cycle of thin low-level clouds above snow and ice in the context of various atmospheric regimes, with different water vapor and aerosol supply pathways and different mechanisms for the formation and sustenance of precipitation. These clouds are routinely missed by satellite observations, and because they are ubiquitous and tend to warm the surface, they contribute significantly to surface melt. In the study area, aircraft observations of the relevant parameters are exceedingly rare. As a result, cloud processes are not well understood in the region, and their predictions are uncertain in models on a range of scales. ARCSIX will not only provide observations to constrain process and numerical weather prediction models, but is also intended to improve remote sensing of key parameters from low Earth orbit. This will be achieved by flying instrument prototypes such as novel water vapor lidars, and by providing ground-truth data for the development of new algorithms for heritage instruments that will benefit a range of missions currently under development. I will put ARCSIX in context with current and future satellite and aircraft missions and discuss our evolving approach for answering the driving science questions.