Abstract. Ensemble simulation of the atmospheric general circulation at altitudes up to the lower thermosphere is performed using the 3-D nonlinear mechanistic numerical model MUAM. The residual mean meridional circulation (RMC), which is the superposition of the mean Eulerian and wave-induced eddy components, is calculated for the boreal winter. Changes in the vertical and meridional RMC velocity components are analysed at different stages of a simulated composite sudden stratospheric warming (SSW) event averaged over 19 model runs. The simulation results show a general decrease in RMC velocity components up to 30 % during and after SSW in the mesosphere and lower thermosphere of the Northern Hemisphere. There are also increases in the downward and northward velocities at altitudes of 20–50 km at the northern polar latitudes during SSW. Associated vertical transport and adiabatic heating can contribute to warming the stratosphere and downward shifting of the stratopause during the composite SSW. The residual mean and eddy mass fluxes are calculated for different SSW stages. It is shown that before the SSW, planetary wave activity creates wave-induced eddy circulation cells in the northern upper stratosphere, which are directed upwards at middle latitudes, northward at high latitudes and downwards near the North Pole. These cells increase heat transport and adiabatic heating in the polar region. During SSW, the region of upward eddy vertical velocity is shifted to high latitudes, but the velocity is still downward near the North Pole. After SSW, upward eddy-induced fluxes span the entire polar region, producing upward transport and adiabatic cooling of the stratosphere and providing the return of the stratopause to higher altitudes. The obtained statistically significant results on the evolution of RMC and eddy circulation at different SSW stages at altitudes up to the lower thermosphere can be useful for a better understanding the mechanisms of planetary wave impacts on the mean flow and for the diagnostics of the transport of conservative tracers in the atmosphere.

Abstract. Ensemble simulation of the general atmospheric circulation of the middle and upper atmosphere up to the lower thermosphere is performed using the 3-D nonlinear mechanistic numerical model MUAM. Residual mean meridional circulation (RMC) in terms of the Transformed Eulerian Mean is calculated for the boreal winter and changes in its vertical and meridional velocity components during different phases of simulated composite stratospheric warming (SW) events are studied. The simulation results show general decrease in RMC velocity components up to 30 % during and after SW in the mesosphere and lower thermosphere of the Northern Hemisphere. There are also increases in the downward and northward velocities at altitudes 50–70 km at the northern high latitudes. Associated changes in adiabatic heating/cooling rates can contribute to heating the stratosphere and cooling the mesosphere during the composite SW. The changes in the transport of conservative species (like ozone) during SWs are estimated. Weakening of ozone fluxes at the middle latitudes of the Northern Hemisphere may reach 30 % during SWs and 30–40 % after the events at the altitudes of stratospheric maximum of ozone concentration. Such statistically confident simulations of RMC reactions on SWs at altitudes up to the lower thermosphere are performed for the first time. The study of the residual meridional circulation is useful for effective analysis of wave impacts on the mean flow and for diagnostics of the transport of atmospheric gas species in the atmosphere.

Abstract. Lakes affect local weather and climate. This influence should be taken into account in NWP models through parameterization. For the atmospheric simulation, global coverage of lake depth data is essential. To provide such data Global Lake Database (GLDB) has been created. GLDB contains information about lake location (latitude, longitude), water surface area, and lake mean and max depths. The mean depth is provided as a gridded data set.

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Analysis of the arrival of southern cyclones to the Republic of Bashkortostan / Volobueva O.V., Toptunova O.N., Drobzheva Y.V. // Hydrometeorological Research and Forecasting, 2021, no. 2 (380), pp. 66-76. The results of the analysis of the arrival of southern cyclones to the territory of the Republic of Bashkortostan for the period of 1993-2018 are presented. Typical trajectories of cyclones, areas of their origin, as well as accompanying adverse weather phenomena are identified according to the observational network of the Bashkir Administration for Hydrometeorology and Environmental Monitoring. In 70 % of cases, southern cyclones move through the territory of the republic and leave it in the southern direction. About 50 % of the depressions come to the Republic of Bashkortostan from the Black Sea and its coast. The upper-air field for the arrival of southern cyclones is the front part of the pressure trough with high geopotential height gradients. The arrivals of southern cyclones have a significant impact on the study area and are closely related to the formation of severe hydrometeorological events. Keywords: southern cyclone, typical territories, the Republic of Bashkortost