The Southern Ocean surrounding Antarctica is the stormiest place on Earth, marked by heavy cloud cover that helps determine how much of the sun’s energy reaches Earth’s surface. Due in part to the scarcity of field data from the region, current climate models have difficulty reproducing the behavior of clouds over the Southern Ocean, which in turn affects how well they can simulate current and future climate. Motivated by these data limitations, an international multi-agency effort collected atmospheric and oceanographic data via ship-, aircraft-, and island-based instrumentation in a...