Perspicacious indicators of atmospheric blocking

A novel dynamically‐based approach is introduced to identify, describe and diagnose atmospheric blocking events. The approach is based upon the potential vorticity perspective and takes into account the three‐dimensional structure of the phenomenon. It is argued that the essence of a blocking anomaly is located in the upper troposphere, just below the tropopause. The associated novel blocking indicators are derived from two‐dimensional fields at 6‐hourly temporal resolution, and provide information on the spatial scale, shape, amplitude and movement of blocks. A northern hemisphere winter (DJF) climatology for the ERA15 period (1979–1993) is presented and comments are made on the relationship between the indicators and previous blocking indices.