The article compares the interannual variability of the atmosphere at the OH glow height, which can be associated with planetary wave propagation, at stations spaced in latitude. As a characteristic reflecting planetary wave activity we consider standard deviations of the average overnight temperature σpw from its monthly average after taking into account the seasonal variation. Joint mesopause temperature measurements at high latitudes at two optical stations Maimaga (63.04° N, 129.51° E) and Tiksi (71.58° N, 128.77° E) began in 2015. The stations are equipped with identical Shamrock (Andor) high image quality infrared spectrographs for registration of OH (3-1) in the near infrared region (~1.5 μm). The main result of studying the planetary wave activity during the 5-year period of simultaneous observations is that at Tiksi station it slightly (by about 1–2 K) exceeds that at Maimaga station. In average annual activity fluctuations, the presence of quasi-biennial oscillations is traced.

At the Institute of Cosmophysical Research and Aeronomy, a meridional network of stations has been created, the purpose of which is to monitor the state of the atmosphere at the height of hydroxyl emission (similar to 87 km). The network covers arctic (Tiksi, 71.5 degrees N, 129 degrees E), subarctic (Maimaga, 63 degrees N, 129.5 degrees E) and middle (Neryungri, 56.39 degrees N, 124.43 degrees E) latitudes. Each station is equipped with a spectrograph with a highly sensitive InGaAs infrared photodiode measuring the OH (3-1) band. This paper presents the characteristics of spectrographs designed to measure the radiation intensity of the OH (3-1) band and determine the temperature from its rotational structure. An original technique for measuring the rotational temperature is described, based on minimizing the deviation of the recorded spectrum from the model by the least square method. Estimates of random and systematic errors showed that at a signal-to-noise ratio more than 20, the temperature measurement error is 2 K. Mutual calibration of the instruments showed that the difference in measurements lies within 2 K. The meridional network of stations is fully automated and controlled remotely via the Internet.

Based on the data of Total Electron Content (TEC) and OH rotational temperature, we analyze temporal and spatial features of the level of short-term variability (within the periods of up to several hours) at the ionosphere and the upper mesosphere. The study is carried out at three points located at mid-latitude, subauroral, and high-latitude regions during for more than 5 years period. The dynamics of variability, both in the ionosphere and at the mesopause, have the similar pattern with a clear seasonal variation. The maximum in the variability is registered in winter, and it exceeds up to 5-6 times the variability level during the summer period. This feature is observed regularly. The revealed dynamics does not correlate with changes the in geomagnetic and solar activities. The variability within considered periods is generally related to activity of Internal Gravity Waves in the upper atmosphere. We suggest that a source of the related seasonal variations in the variability may be the stratospheric high-velocity jet stream that develops in the subauroral regions during winter months. We propose a stratosphere disturbance index based on Era-5 Reanalysis data. The index is shown to have a maximum at subpolar regions and experience the similar regular seasonal variation with a maximum during winter months. We show a clear correlation between the mesosphere/ionosphere variability indices and the stratosphere disturbance index. The obtained results indicate a strong coupling between the short-period variability in the ionosphere, in the upper mesosphere, and in the subauroral stratosphere. The study is supported by the Russian Science Foundation Grant No. 20-77-00070.

Results of the study of the temperature in the mesopause region (∼87 km) based on measurement of OH (3-1) emission at the high latitude station Maimaga (63.04° N, 129.51° E) are presented and compared with the Aura (MLS) measurements of temperature at 0.002 hPa in 2013–2018 when flying over the Maimaga station. The average rotational temperature of OH (3-1) was compared with temperatures measured by Aura (MLS) and the background temperatures calculated from them. The results show more correct comparison of the OH (3-1) temperature with the background temperature calculated from Aura (MLS) data. The comparison confirms the observation of high temperatures in the mesopause in winter 2014/2015. In general, the temperature variations measured by two different methods are qualitatively consistent and answer the seasonal variations. Temperature differences can be explained by many factors, e.g., differences in measuring altitudes and techniques.

Temperature data of the mesopause region, obtained for the period 1999-2016 at the Maimaga station (63.04°N, 129.51°E), were studied. Registration of spectra was carried out with the help of light-sensitive infrared spectrographs SP-50, recording the OH (6-2) band. The standard deviation of temperature σpw from its average monthly value after deduction of seasonal temperature course is accepted as a characteristic of planetary wave activity. There is a quasi two-year cycle of planetary wave activity. A correlation is observed between the activity of planetary waves and the F10.7cm index.

We perform a joint analysis of short-period (up to several hours) variability in parameters of the ionosphere, the mesosphere, and the stratosphere at mid-latitude, subauroral, and high-latitude points for a long time interval. The study is based on the ionospheric total electron content (TEC) measurements and data on the OH rotational temperature at the mesopause height. We reveal similar seasonal variations in the dynamics of the short-term variability level, both in the ionosphere and the mesosphere. Maximum variability is observed during winter months and it exceeds the values in summer period up to 5–6 times. The revealed dynamics has no explicit relation to the levels of geomagnetic and solar activities. We suggest that the instabilities in the high-velocity stratospheric subauroral winter jet stream may be a source of the recorded variability seasonal variations in the ionosphere and the mesosphere. We propose a new index to estimate a short-term variability in the stratosphere. The index is shown to experience similar regular seasonal variations with a maximum during winter months. We show a clear correlation between the mesosphere/ionosphere variability indices values and the stratosphere disturbance index. The correlation is shown to be higher for the mesosphere variability index as compared with that in the ionosphere, and at the high-latitude point located closer to the jet stream. The obtained results indicate a strong interrelation between the short-period variability in the ionosphere, in the upper mesosphere, and in the subauroral stratosphere. The results contribute to elucidating the basic mechanisms for a vertical coupling between different atmospheric layers.

The analysis of changes in temperature of mesopause region based on fluctuation measurements of rotational temperature and intensity of molecular emission of hydroxyl OH (6-2) excited at ∼87 km altitude is presented. Observations were carried out at the Maimaga station (63°N, 129.5°E), at a distance of 120 km to the north from Yakutsk. Measurements were conducted with a digital infrared spectrograph. The temperature was determined from the distribution of the emission intensity in the different branches of the molecular hydroxyl band. Comparison OH(6-2) temperature with the calculated data of NRLMSISE-00 model was defined based on the data received from 1999 to 2015. 2320 midnight temperature values of hydroxyl OH (6-2) suitable for comparison were obtained at the Maimaga station over 16 years of measurements. The NRLMSISE-00 model describes temperature changes at the height of the mesopause region from October to April within the experimental fluctuations with a seasonal temperature variation of ∼ 35 K, deviations from the experimental values are no more than 7 ± 4 K. A correlation analysis was performed to compare the rotational temperature OH (6-2) and the NRLMSISE-00 model calculations. When the number of observations at the station Maimaga more than 180 days (about six months) correlation coefficient R> 0.7. This means that the NRLMSISE-00 model accurately describes the temperature changes of the subauroral mesopause.

Исследованы данные температуры области мезопаузы, полученные за период 2013-2018 гг. на станции Маймага (63.04N, 129.51E) и за период 2015-2018 гг. на станции Тикси (71.58 N, 128.77 E). В зимний период сезона наблюдений 2014-2015 характеристика активности внутренних гравитационных волн (ВГВ) gwимеет более низкие значения, чем в другие сезоны, а средненочная температура, наоборот, превышает аналогичные значения в другие сезоны. Для сопоставления рассматривались спутниковые данные температурных профилей полученные EOS MLS (Aura). После выделения и вычитания вклада гравитационной составляющей из температурных профилей EOS MLS для области над станцией Маймага заметно отличие в зимней стратопаузе сезона 2014-2015. В этот сезон в зимний период, с учетом вычета вклада флуктуаций температуры обусловленных ВГВ, наблюдается отсутствие резких потеплений в районе стратопаузы в отличие от остальных сезонов. Измерение параметров планетарных волн в течение периода 2015-2018 гг. совместных наблюдений на станциях Маймага и Тикси показали, что фазы наблюдаемых на обеих станциях волн совпадают, а амплитуды на станции Тикси несколько (12 К) превышают амплитуды на станции Маймага. The temperature data of the mesopause region obtained for the period 2013-2018 at the station Maimaga (63.04 N, 129.51 E) and for the period 2015-2018 at the station Tiksi (71.58 N, 128.77 E) was investigated. During the winter period of the 20142015 observation season, the characteristic of the internal gravity waves (IGW) activity sgw has lower values than in other seasons, and the average night temperature of the mesopause region, on the contrary, exceeds corresponding values in other seasons. For comparison, satellite data of temperature profiles obtained by EOS MLS (Aura) are given. After isolating and subtracting the contribution of the gravitaty waves from the EOS MLS temperature profiles for the region above the st. Maimaga, the difference in the winter stratopause of the 2014-2015 season is noticeable. In this season in winter there is a lack of sharp warming in the stratopause region, in contrast to other seasons, taking into account the deduction of the contribution of temperature fluctuations due to IGW. Measurement of the parameters of planetary waves during the period 2015-2018 of joint observations at Maimaga and Tiksi stations showed that the phases of the waves observed at both stations coincide, and the amplitudes at Tiksi station are several (1-2 K) higher than the amplitudes at Maimaga station.

The temperature data of the mesopause region obtained for the period 2013-2018 at the station Maimaga (63.04 degrees N, 129.51 degrees E) was investigated. During the winter period of the 2014-2015 observation season, the characteristic of the internal gravity waves (IGW) activity sigma(gw) has lower values than in other seasons, and the average night temperature of the mesopause region, on the contrary, exceeds corresponding values in other seasons. For comparison, satellite data of temperature profiles obtained by EOS MLS (Aura) are given. After isolating and subtracting the contribution of the gravitational component from the EOS MLS temperature profiles for the region above the Maimaga station, the difference in the winter stratopause of the 2014-2015 season is noticeable. During this season, the winter stratopause has lower temperatures than in other seasons, taking into account the deduction of the contribution of temperature fluctuations due to IGW.

The temperature of the mesopause region (87 km) is monitored at the Maimaga station (63.04 ° N, 129.51 ° E) using the Shamrock (Andor) spectrograph recording the hydroxyl (OH) band (3, 1). The temperature data obtained for the seasons from 2013 to 2017 are investigated. The standard deviations corresponding to the internal gravity σgw and tidal waves σtd were obtained. The seasonal course of the tidal component σtd varies from 2 to 5 K throughout all observation seasons. The seasonal variation of the gravitational component σgw observed at Maimaga station almost coincides for three observation seasons except for the 2014-2015 season. In this observation season, σgw has lower values in winter than in other seasons. Moreover, in this season average monthly temperatures exceed similar values in other seasons.

Maimaga (63° N, λ = 129.5° E) is a base point in the meridional station network that we create in East Siberia to monitor changes in the upper mesosphere. Therefore, the comparison of measurements obtained by ground-based instruments and satellite data are relevant. It is known that the rotational temperature of hydroxyl (OH) corresponds to the temperature of the neutral atmosphere at the height of its radiation (∼87 km). The night spectrum of OH(3-1) is measured by a new Shamrock 303i spectrograph since January 2013. The rotational temperature, estimated from the ratio of the P - branches, is compared with the kinetic temperature of the atmosphere at an altitude of 87 km measured with the SABER radiometer installed aboard the TIMED satellite. The v2.0 version of the SABER temperature profiles was used (http://saber.larc.nasa.gov). The SABER measurements obtained within the area (55°N-70°N)×(115°E-135°E) have been selected. The angle of view of the ground-based spectrograph is almost in the center of the selected area. The satellite overpasses the selected area only in September-November and January-March. The spectrograph measurement is considered if the difference in time from the satellite measurement does not exceed a half of hour. The analysis of 328 cases of coincident measurements has shown that the difference in temperatures obtained from the satellite and ground-based spectrograph lies within the errors of both instruments. The correlation coefficient between two databases is equal 0.8. Based on the performed analysis, it has been concluded that a series of hydroxyl rotational temperatures can be used to study temperature variations of different time scales including long-term trends at the OH emission altitude (∼87 km).

The temperature of the mesopause region (87 km) is monitored at the Maimaga station (63.04° N, 129.51° E) using the Shamrock (Andor) spectrograph recording the OH band (3, 1). The temperature data obtained for the seasons from 2013 to 2017 are investigated. Standard temperature deviations σgw corresponding to internal gravity waves are obtained. The seasonal variation of the gravitational component of standard deviations of temperature σgw observed at Maimaga station almost coincides for three observation seasons except for the 2014-2015 season. In this observation season, σgw has lower values in winter than in other seasons. In addition, in the 2014-2015 season, average monthly temperatures exceed similar values in other seasons.

Since 2013, the optical station of Maimaga (63° N, 129.5° E) has been continuously recording the OH(3,1) hydroxyl band with a spectrograph operating in the near-infrared region (~1.5 μm). In September 2015, a similar spectrograph was mounted at the polar geophysical observatory located in the Tiksi urban locality (71.6° N, 128.7° E). The present work compares the seasonal variation of the mesopause temperature measured at two different- latitude stations. In addition, preliminary comparisons are made for overnight variations for several nights. The comparison shows that there is a very good correlation between data obtained at the two stations, with a correlation coefficient of 0.83. A comparison with the predictions of the CIRA and MSIS empirical atmospheric models revealed a number of discrepancies.

Since 2015, simultaneous observations of temperature of the high-latitude mesopause (87 km) have been made at Maimaga (63.04° N, 129.51° E) and Tiksi (71.58° N, 128.77° E) stations. These stations record spectra with Shamrock (Andor) photosensitive infrared spectrographs detecting the OH (3, 1) band in the near-infrared region (about 1.5 μm). We analyze temperature data obtained in observation seasons from 2015 to 2017. Standard deviations of temperature σ from its mean values are taken as characteristics of wave activity at night. We have obtained standard temperature deviations corresponding to internal gravity waves (IGW) (σgw) and tidal waves (σtd). Mean night rotational temperatures of hydroxyl emission almost coincide, and seasonal variations of gravity and tidal waves have a similar form during two seasons of simultaneous observations at Tiksi and Maimaga.

Аннотация. Область мезопаузы 80-100 км как область атмосферы с крайне изменчивой и наиболее низкой температурой вызывает большой исследовательский интерес. Волновая активность вносит существенный вклад в температурный режим мезопаузы, и для понимания температурного поведения мезопаузы и близлежащих областей необходимо ее тщательное изучение. На высотах мезосферы и нижней термосферы волновую активность исследуют как методом спутниковых измерений, так и с помощью наземных наблюдений. Наиболее распространенными и доступными среди наземных методов являются спектральные наблюдения эмиссий гидроксила OH (3, 1), которые возбуждаются в области мезопаузы. Вращательная температура, определяемая по распределениюинтенсивности в полосе гидроксила (ОН), является близкой к кинетической температуре нейтрального газа на высоте излучения. На станции Маймага (63.04° N, 129.51° E) с 2013 года ведется наблюдение температуры высокоширотной мезопаузы (87 км) с помощью спектрографа Shamrock (Andor), регистрирующего полосу ОН (3, 1). Исследованы данные температуры, полученные за сезоны с 2013 по 2017 гг. Выделены стандартные отклонения температуры, соответствующие внутренним гравитационным волнам σgw и приливным волнам σtd. Сезонный ход приливной компоненты стандартных отклонений температуры σtd варьирует от 2 до 5 К на протяжении всех сезонов наблюдений. Наблюдаемый на станции Маймага сезонный ход и значения гравитационной компоненты стандартных отклонений температуры σgw почти совпадают для трех сезонов наблюдений кроме сезона 2014-2015 гг. В этом сезоне наблюдений σgw имеет более низкие значения в зимний период, чем в остальные сезоны наблюдений. Кроме того, в сезоне 2014-2015 гг. среднемесячные температуры зимней мезопаузы превышают аналогичные значения в другие сезоны. Сезонное изменение гравитационной составляющей варьирует от 2 до 6 К, а в сезоне 2014-2015 – от 1.5 до 5 К. Более низкие показатели активности ВГВ в зимний период сезона 2014-2015 гг. могут быть объяснены тем, что, возможно, в этот сезон значительная часть энергии ВГВ была поглощена на высоте, близкой к высоте эмиссионного слоя, что подтверждается наблюдаемой повышенной среднемесячной температурой в этот период. Для дальнейших исследований планируется обработкатемпературных данных со спутников Aura/MLS и TIMED/SABER.

A new infrared spectrograph with high temporal resolution for observation of OH band (3-1) emission dynamics is described. For the automated work of the spectrograph, special software was created. Remote control over the device is also configured.