Koval, A.V., Didenko, K.A., Ermakova, T.S., Gavrilov, N.M., Sokolov, A.V. Changes in general circulation of the middle and upper atmosphere associated with main and transitional QBO phases. Advances in Space Research, 2024, V. 74(10), P. 4793-4808б https://doi.org/10.1016/j.asr.2024.07.037, Q1
Abstract
Three-dimensional numerical nonlinear model of general circulation of the middle and upper atmosphere (MUAM) is used to simulate changes in the atmospheric dynamical and thermal regimes related to changes in phases of equatorial stratospheric quasi-biennial oscillation (QBO). In addition to conventional (easterly and westerly) QBO phases, two transitional: westerly-shear (wsQBO, from easterly to westerly) and easterly-shear (esQBO, from westerly to easterly) QBO phases are added into consideration in order to research in details QBO-induced changes in global circulation and interactions of planetary waves (PWs) with the mean flow. To interpret the obtained results, the residual meridional circulation, Eliassen-Palm fluxes and meridional temperature gradients are calculated based on MUAM ensemble simulations for the four QBO phases.
The simulation results showed different temperature and zonal wind structures in the extratropical winter stratosphere at different QBO phases. The esQBO transition phase is characterized by the strongest temperature and zonal wind changes. This is obtained both from the simulation and from the reanalysis data, and can be explained by PW influence directly through changes in Eliassen-Palm flux and indirectly through modifications in the meridional circulation. Abrupt changes in the subpolar stratosphere during esQBO are gradually compensated for the next 3 phases. Changes in the zonal wind in the thermosphere due to the QBO phases changes can reach 10 %. An increase in wave activity in the Northern Hemisphere is accompanied by a weakening of the zonal wind during the esQBO and eQBO phases above approximately 150 km.
Published online: July 2024