Forecast models of cloud coverage over the Arctic oceans are unable to accurately predict the amount of cloud cover that will form. One major contributor to the model inaccuracy is poor representation of cloud droplets and frozen cloud particles. To measure how cloud droplets and frozen cloud particles form and grow within Arctic clouds, a research aircraft flew into clouds over the ocean between Greenland and Norway during a project called CAESAR (Cold Air outbreak Experiment in the Sub-Arctic Region). Instruments onboard the aircraft measured the properties of ice crystals and cloud droplets within these clouds.

Furthermore, a novel method of measuring the history of how ice particles formed within these clouds is tested for the first time. This approach uses sensitive measurements of stable water isotopes within the cloud particles. These water isotopes serve as tracers that provide information about the temperature and humidity that the cloud particles experienced during their lifetime. The isotope measurement can also indicate whether ice particles were once liquid before freezing or if they grew directly as ice.

These measurements help improve our understanding of how cloud droplets and ice behave in Arctic clouds, leading to improvements in cloud modeling.