Long-term trends in the middle atmosphere dynamics at northern middle latitudes – one regime or two different regimes?

Abstract. Due to increasing atmospheric concentration of greenhouse gases and changing stratospheric ozone concentration, both of anthropogenic origin, various quantities in the middle atmosphere reveal long-term changes and trends. Lastovicka and Krizan (2006) indicated possibility of change of trends in the dynamics in the northern midlatitude middle atmosphere as a whole in the 1990s. To search for such change of trends we use data on winds in the mesopause region, on total columnar ozone, on ozone laminae, on winds in the middle and lower stratosphere, and on peak electron density in the E region of the ionosphere. One group of quantities, the mesopause region wind-like trends, changes their trends around 1990, the other one, the total ozone-like trends, in the mid-1990s. Altogether they create a skeleton of scenario of the change of the middle atmosphere dynamics trends in the 1990s. Drivers of these changes appear to be different for the first group and for the second group. Tropospheric processes seem to play a role in the changes of trends in middle atmospheric dynamics.