LOW-FREQUENCY VARIABILITY OF WINTER ATMOSPHERIC CIRCULATION IN THE NORTHERN HEMISPHERE

M. P. Aleksandrova, E. M. Volodin, E. A. Gazina, and N. N. Sokolikhina

Analysis of the spatial and temporal variability of long-period variations of the Northern Hemisphere tropospheric and stratospheric parameters in the winter season reproduced by the atmospheric general circulation model of the Institute of Numerical Mathematics, Russian Academy of Sciences, has shown that the model correctly simulates the main features of low-frequency variability of atmospheric circulation. It is shown that the North Atlantic Oscillation is found not only in surface data but also in the field of absolute geopotential and zonal wind up to the lower stratosphere. Besides, the analysis of expansion of zonal mean fields in natural empirical components has demonstrated that the westerly flow prevails in about 30% of cases in both the lower and upper troposphere and extends even to the lower stratosphere (about 20 hPa).