Gridded Polar Atmospheric River (AR) scale dataset

The gridded polar Atmospheric River (AR) scale dataset is calculated based on the extended AR scale developed at the Center for Western Weather and Water Extremes (CW3E) at Scripps Institution of Oceanography, which ranks ARs from AR P1 to AR5 at each grid point based on ERA5 data (1°×1°) at hourly temporal resolution from 1979-2022. This AR Scale accounts for both integrated water vapor transport (IVT) maximum value at the AR core and the AR duration. It was thoroughly tested during the Year of Polar Prediction in the Southern Hemisphere (YOPP-SH) Winter Targeted Observing Periods and has proven effective in accurately reflecting the strength and duration of ARs, aiding both forecast operations and research. No filter method has been applied.