Numerical simulation of the mean meridional circulation in the middle atmosphere at different phases of stratospheric warmings and mountain wave scenarios

Abstract

Abstract In this study, numerical simulations have been performed to estimate the transformation of the mean meridional circulation in altitude range 0–100\u202fkm\u202fat different phases of simulated stratospheric warming (SW) events in January–February including and excluding impact of mesoscale orographic gravity waves (OGWs). To obtain an ensemble of 12 pairs of model runs with and without a parameterization of OGW effects, the numerical middle and upper atmosphere model (MUAM) has been used. Obtained results demonstrate weakening of the zonal mean meridional circulation at altitudes up to 100\u202fkm during and after simulated SWs compared to the time interval before SWs. At altitudes below 50\u202fkm, southward mean meridional winds decrease (up to 15%) before and after simulated SWs. OGW effects may increase the mean northward wind at altitudes above 60\u202fkm up to 10–15%. The most significant changes of the meridional circulation in the middle atmosphere are detected at the middle and high latitudes of the Northern Hemisphere: the southward meridional circulation increases at altitudes above 40\u202fkm and decreases below 40\u202fkm. Thus, the global-scale mean meridional circulation in the middle atmosphere may significantly depend on different phases of SW events during the northern winter season. It is also quite sensitive to the dynamical and thermal OGW impacts.