A modified time-longitude diagram applied to 500 mb heights along 50° north and south

Abstract

The common time-longitude section (or Hovmöller diagram) shows longitude and intensity of troughs and ridges as a function of time. It is modified to a time-longitude lag-correlation diagram to yield statistically relevant estimates of zonal wavelengths, phase and group velocities. Different scales can be distinguished after the data sets have been treated by band- and low-pass filters. The lag-correlation analysis is applied to the 500 mb geopotential height along 50°N and 50°S for individual basepoints and averaged over the latitude circle. This technique is also useful if the local or zonally averaged dynamics of numerical models is to be statistically verified.