Climatology and annual displacement of the upper-level frontal zones in the middle troposphere of the Northern Hemisphere

An updated climatology of upper level frontal zones (UFZ) of the Northern Hemisphere is presented, based on a numerical analysis of geopotential gradients and the allocation of maximum gradient zones. Differences in the position of the UFZ during the development of meridional and zonal processes are revealed. Based on the analysis of years with the predominance of various forms of circulation, it is shown that the position of high-altitude frontal zones is an objective diagnostic tool for studying modern climate variability.