Winter climatology of upper-level frontal zones in the Northern Hemisphere

Average long-term fields of geopotential gradients in the middle and upper troposphere and temperature gradients and geopotential Laplacian in the middle troposphere in the Northern Hemisphere in winter are analyzed. Based on the analysis of the distribution of the maximum values of gradients, the average long-term position of upper-level frontal zones and their axial lines was determined. Their spatial distribution is analyzed from the point of view of interaction between thermobaric fields over different regions of the globe. Average long-term parameters of upper-level frontal zones in the middle troposphere are presented. Average long-term fields of wind speed in the middle and upper troposphere are investigated. It is demonstrated that the zones of the maximum values of wind speed agree well with the position of separated upper-level frontal zones.