Investigating Summer 2022 Arctic Cyclone Structure and Evolution

Abstract

Arctic cyclones have large impacts on sea-ice redistribution and are hazardous to com-munities in the region, yet the structure and evolution of summer Arctic cyclones is not fully understood. The structure and evolution of summer 2022 Arctic cyclones are investigated using Community Earth Systems Model (CESM) atmosphere-only simu- lations nudged to European Centre for Medium Range Weather Forecasts (ECMWF) fifth generation reanalysis (ERA5). We explore the bias of cyclones compared to ERA5 simulated in CESM when nudging to the full-atmosphere, above the boundary layer only, and above the troposphere only. Full-atmosphere and above the bound- ary layer only nudged runs compare reasonably well to ERA5 in cyclone location, structure, and evolution. A case study analysis demonstrated a warm core cyclone interacted with a tropospheric polar vortex (TPV) before maturation, which show- cased the transition between a vertically and horizontally asymmetric storm to a more axisymmetric storm at maturation in both CESM and ERA5. A composite analysis of Arctic cyclones in the full-atmosphere and above the boundary layer only nudged runs showed warm core and cold core cyclones had distinct thermodynamic and dynamic structures, but combining all cyclones leads to similar structure as in previous studies. The biases compared to ERA5 when nudging CESM only above the boundary layer or above the troposphere are largely due to the different boundary layer and cloud physics parameterizations in ERA5 and CESM, so observational comparison is war- ranted to contextualize these results. Future work includes observational comparison, utilizing a higher resolution grid, and evaluating the boundary layer parameterization in CESM.