Koval, A.V., Gavrilov, N.M., Pogoreltsev, A.I., Kandieva, K.K., Dynamical impacts of stratospheric QBO on the global circulation up to the lower thermosphere // Journal of Geophysical Research: Atmospheres, 127, e2021JD036095, 2022. doi:10.1029/2021JD036095
Abstract:
To estimate reaction of the atmospheric circulation in the middle and upper atmosphere to changes in phases of equatorial stratospheric quasi-biennial oscillation (QBO), the three-dimensional nonlinear middle and upper atmosphere model (MUAM) is used. This model allows continuous simulations of atmospheric wave propagation from the ground to the thermosphere (300 km and above). The main atmospheric hydrodynamic fields (wind and temperature), components of residual meridional circulation (RMC), and fluxes of mass are calculated based on ensembles containing 16 pairs of model runs for initial conditions corresponding to easterly and westerly QBO phases. To minimize uncertainties in determination of the QBO phases, an approach based on the usage of empirical orthogonal functions (EOFs) is applied. Statistically significant results are obtained illustrating how changes in the planetary waves (PWs) structures promote the spread of QBO effects to polar latitudes and to the thermosphere, through changes in the Eliassen-Palm (EP) flux and its divergence, or through the formation of an eddy meridional circulation. The main contribution to the cooling of the polar winter stratosphere during the westerly QBO is made by the weakening of wave activity, in particular, the weakening of the vertical EP flux, which leads to a weakening of the poleward heat flux. The sensitivity of the wave-induced eddy circulation to changes in the QBO phase is higher than that of the RMC, demonstrating that PWs propagating from the lower troposphere are the most important mechanism for the transfer of global circulation disturbances from the equatorial QBO region to polar latitudes