Fig. 1: Arctic cyclone activity index.
From: Arctic cyclones have become more intense and longer-lived over the past seven decades
The standardized energy-based cyclone activity index (EnCAI) for the Arctic (north of 60°N) from January 1950 to December 2021 for the NCEP-NCAR (green curve), ERA5 (blue curve), and JRA-55 (gray curve) datasets. The red curve shows the multi-dataset mean EnCAI. The red straight line is a linear trend of the mean EnCAI. The gray shading indicates ±1.0 the standard deviation relative to the linear trend.
