Trends in the interannual variability of the wave activity of planetary waves in the middle atmosphere

The trends in the wave activity variations of planetary waves for the period from 1980 to 2021 were estimated using the JRA-55 reanalysis data. At the first study phase wave activity was studied within the framework of the classical approach. The vertical component of the wave activity flux was averaged over three latitude–longitude sectors of the Northern Hemisphere for December through March, time series were constructed, and the significance of the detected trends was evaluated. Statistical estimation of the calculated trends of wave activity fluxes showed an increase in the wave activity rising from the troposphere to the stratosphere in January and March over the Russian Far East. The interannual decrease of the upward component of the flux since 1980 is observed only in December over the European part of Russia, Europe, and the Middle East.

Wave activity was studied as a potential enstrophy variations over time or as a time change in the  Ertel’s potential vorticity squared in addition to the classical approach. In this case, the interannual variability of the wave activity of individual planetary waves, in particular, a stationary planetary wave with a zonal wave number of 1 and 2 was analyzed. Wave activity changes were calculated for the 30 km level and were also averaged for December, January, February and March. It is found that a statistically significant trend of wave activity of a stationary planetary wave with a zonal wave number of 1 increase in time is observed in December. The trend is significant with a 90% probability. A statistically significant trend with a probability of 80% was obtained for a change in the wave activity of a stationary planetary wave with a zonal wave number of 2 over time in December and March. At the same time, wave activity weakens in December, and increases in March.