The sensitivity analysis of Arctic cyclone structure and characteristics in ensemble forecast

Sea ice cover in the Arctic has declined significantly during summer over the past few decades, leading to the opening up of Arctic shipping routes. However, the prediction of Arctic cyclones, which plays an important role in shipping safety, still has room for improvement. Cyclones interact with the underlying sea ice leading to potential modification of the cyclone through changes in the fluxes of heat, moisture and momentum into the atmospheric boundary layer from the sea surface. At the same time, Arctic cyclones can have different structures from extratropical cyclones, such as tropopause polar vortices  (TPVs), which may enhance the predictability of Arctic cyclones. Therefore, further understanding of the structure and lifecycle of cyclones in the Arctic region is crucial to improving forecasts.

In this presentation, a case study, the third cyclone observed time Arctic cyclones field campaign in 2022 (cyclone3), is discussed, to find out the relationship between the structure and characteristics of the cyclone and precursor fields. Cyclone3 lasted 13 days and travelled from the Greenland Sea across the North Pole to the Laptev Sea before returning to the Greenland sector. Because of its long lifetime and moving track, we can find out how its property changes over different surface types. Ensemble sensitivity analysis (ESA) is used to learn how the spread of cyclone outcomes in the ensemble forecast are related to early state variables, such as surface fluxes and TPVs, to understand how the prediction of cyclone evolution, including the structure and intensity, changes in different cyclone stages, and what that tells us about how upper- and lower-level dynamics interact in the Arctic region.