Dynamics of Zonally Averaged Circulation Characteristics in the Middle Atmosphere
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mics of Zonally Averaged Circulation Characteristics in the Middle Atmosphere O. S. Zorkaltsevaa, b, *, V. I. Mordvinova, A. I. Pogoreltsevc, d, and N. S. Dombrovskayaa a Institute
of Solar-Terrestrial Physics, Siberian Branch, Russian Academy of Sciences, Irkutsk, 664033 Russia b Irkutsk State University, Irkutsk, 664033 Russia c Russian State Hydrometeorological University, St. Petersburg, 195196 Russia d St. Petersburg State University, Peterhof, 198504 Russia *e-mail: [email protected] Received September 26, 2019; revised January 29, 2020; accepted February 5, 2020
Abstract—The ERA-Interim archive data and circulation calculations using a middle and upper atmosphere model (MUAM) have been used to study dynamic processes in the middle atmosphere. Variations in zonally averaged atmospheric characteristics have been analyzed based on observational data and model calculations. In the middle atmosphere within a range of 10–30 days, synchronous temperature variations are observed within zones extended horizontally and vertically. Horizontally, the sign of such variations changes in the region of jet streams (and remains unchanged at the equator) and, vertically, their sign changes within the stratopause and mesopause regions. The nature of these variations is almost independent of the phase of the quasi-biennial cycle in the equatorial stratosphere. These variations are global in nature and similar to oscillations in meridional circulation cells. Keywords: stratosphere, mesosphere, sudden stratospheric warming, quasi-biennial oscillation DOI: 10.1134/S0001433820040118
1. INTRODUCTION The low-frequency atmospheric variability within periods of 10–30 days includes variations caused by traveling Rossby waves, quasi-stationary waves associated with both orographic and thermal anomalies, and nonlinear interactions [1, 2]. One of the most complex dynamic phenomena in the middle atmosphere is a sudden stratospheric warming (SSW) [3–5], during which the polar vortex breaks down. In this case, in the high latitudes, the air temperature may rise several tens of degrees. Throughout almost the entire middleatmosphere thickness, zonally averaged meteorological parameters (such as velocity, temperature, etc.) that characterize the polar vortex dynamics significantly vary and both thermal and baric anomalies increase along latitude circles. One can morphologically represent the SSW as a result of the dynamic interaction between the polar cyclonic vortex and one or a few anticyclonic vortices in the middle atmosphere [6]. The SSW is associated with intrinsic instabilities of jet streams in the middle atmosphere [7–9] or with external factors, such as stationary planetary waves propagating from the troposphere, blockings, and disturbances caused by convective processes in the tropics [3, 6, 10]. However, it is unclear to what extent these mechanisms are related, whether the SSW is, to
a greater extent, an explosive amplification of natural oscillations in the middle atmosphere or a result of external energy transportation and
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