Influence of sudden stratospheric warming on the mesosphere/lower thermosphere from the hydroxyl emission observations and numerical simulations.

Abstract We present the results of studying the behavior of temperature and of the atomic oxygen concentration in the mesopause region during the 2013 January major Sudden Stratospheric Warming (SSW). The data on the hydroxyl molecule OH(6-2), 834.0 nm emission intensity and rotational temperature were analyzed. These data were obtained through spectrometric measurements at the Geophysical Observatory of the Institute of Solar-Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences (51.8°N, 103.1°E, Tory), and at the Zvenigorod Station at the Obukhov Institute of Atmospheric Physics of the Russian Academy of Sciences (55.7°N, 36.8 E°). We calculated the concentration of atomic oxygen and its variations by using the data of the OH emission measurements. We revealed, that the response of the mesopause characteristics for two longitudinally spaced mid-latitude regions essentially differs. Thus, from the Tory Station data, the maximal increase in the OH emission intensity (by a factor of ∼2) and in the concentration [O] (by a factor of ∼3) occurred during the sudden stratospheric warming (SSW) evolution, whereas, from the Zvenigorod Station data, the OH emission intensity increase (by a factor of ∼3) and the concentration [O] increase (by a factor of ∼3.5) was observed at the SSW recovery phase. As a result of numerical modeling using the Middle and Upper Atmosphere Model (MUAM), it was shown, that the cause for the revealed effect may probably be longitudinal differences in the diurnal variation in the vertical wind at the mesopause heights over the indicated stations during the SSW. One may elucidate these differences through the generation of non-migrating tides due to a non-linear interaction between the intensified stationary planetary wave 1 (SPW1) and migrating tides and forcing a set of high-frequency PWs at the stratospheric heights. All these waves are capably of propagating into the MLT region and produce observed changes in behavior of the OH emission intensity, temperature and atomic oxygen concentration over Tory and Zvenigorod. Highlights • Effects of 2013 SSW on the MLT for two longitudinally spaced mid-latitude sites are investigated. • Longitudinal differences in the behavior of the mesopause temperature and composition were found. • It may be caused by longitudinal differences in the diurnal variation of vertical wind. [ABSTRACT FROM AUTHOR]