Evidence of change after 2001 in the seasonal behaviour of the mesopause region from airglow data at El Leoncito

Airglow intensities and rotational temperatures of the OH(6-2) and O₂b(0-1) bands acquired at El Leoncito (32°S, 69°W) provide good annual coverage in 1998–2002, 2006, and 2007, with between 192 and 311 nights of observation per year. These data can therefore be used to derive the seasonal variations during each of these seven years, in airglow brightness and temperatures at altitudes of 87 and 95 km. From 1998 to 2001, seasonal variations are similar enough so that they can be well represented by a mean climatology, for each parameter. On the other hand, these climatologies do not agree with what is usually observed at other sites, maybe due to the particular orographic conditions at El Leoncito. With respect to the last three fully documented years (2002, 2006, and 2007), the similarity from year to year deteriorates, and there are greater differences in the seasonal behaviour, more or less in all the parameters. The differences include, e.g., maxima occurring earlier or later than “normal”, by one or two months. All this may suggest the build-up of a new regime of intraseasonal variability, with a possible relationship to corresponding changes in wave activity.     

重力波对中层顶区光化加热的影响

计算了重力波过程对光化加热的影响,并研究了不同温度背景及不同氧原子的背景分析对该过程的影响,计算表明重力波可以造成中层顶光反应加热的损失。     

Variability of mesopause temperature from the hydroxyl airglow observations over mid-latitudinal sites,Zvenigorod and Tory,Russia

We obtained data on temperature in the mesopause vicinity from ground-based observations of the hydroxyl airglow at mid-latitudinal sites, Zvenigorod (56°N, 37°E), located near Moscow, over 2000–2012, and Tory (52°N, 103°E), Eastern Siberia, over 2008–2012. Seasonal behavior of the temperature and its monthly and nightly mean variances are presented. A comparison of the results obtained at two different regions of Russia shows higher values of the mesopause temperature variability in Eastern Siberia. We perform an analysis of the multi-year changes in the temperature variability characteristics based on the Zvenigorod observational data.     

Coordinated lidar and TIMED observations of the quasi-two-day wave during August 2002–2004 and possible quasi-biennial oscillation influence

The Colorado State University sodium lidar, located in Fort Collins, CO (41N, 105W), is capable of both daytime and nighttime operations and has conducted a number of continuous multiple-day observational campaigns over the past few years. Three such campaigns, lasting between 80 and 90 h, were conducted during August 2002–2004 when mesospheric winds and temperature observations were collected simultaneously. These data were processed to extract the vertical structure and temporal evolution of the quasi-two-day wave, which was found to be significant in the power spectra. The quasi-two-day wave in temperature, zonal wind and meridional wind was analyzed for each year, indicating that the wave activity in 2003 was weaker than the other two years. Concurrent TIMED/SABER (2002–2004) and TIMED/TIDI observations (2004) in August were also processed. The SABER temperature shows a quasi-two-day wave with a dominant westward propagating zonal wavenumber four (s = −4) component in 2002 and 2004 but not in 2003. Analysis of the TIDI winds in August 2004 also indicates significant quasi-two-day wave activity, with the zonal wavenumber three and four components of comparable strength. The results of this coordinated ground-based lidar and TIMED satellite observations during August are presented. The possible influence of quasi-biennial oscillation on the inter-annual variability of the quasi-two-day wave is investigated.     

TIMED卫星探测的全球大气温度分布及其与经验模式的比较

利用TIMED卫星遥感探测的全球温度分布与NRLMSISE-00大气经验模式进行了对比研究.研究表明,在中间层下部以下的高度范围内,经验模式与卫星探测的大气温度分布有很好的一致性.但是比较发现,在中层顶区域,经验模式的计算结果与实测结果有较大的差异.卫星探测表明,在春分季节的低纬地区中层顶区存在稳定的逆温层,但是经验模式不能给出低纬地区春分季节中间层逆温层的分布特征.卫星观测表明在全球范围内中层顶有两个非常不同的高度,一个处于100km附近,另一个处于85km附近,但是经验模式不能给出这一中层顶高度的分布特征.同时在低热层,经验模式计算的温度分布与卫星遥感的探测结果有很大的差异.      

A Method of Inversing the Peak Density of Atomic Oxygen Vertical Distribution in the MLT Region From the OI (557.7nm) Night Airglow Intensity

In this paper, using the MSISE-90 model as the reference atmosphere, we discuss the feasibility and method of deducing the peak densities of the undisturbed atomic oxygen profiles in the MLT region (the mesosphere and lower thermosphere region) from OI (557.7 nm) night airglow intersities. The peak densities for different seasons, latitudes and longitudes are deduced from OI (557.7nm) airglow intensities through this expression. We analyze the features of inversion relative errors and discuss the influence of the variations in temperature on inversion errors. The results indicate that all inversion errors are less than 5% except for those at high altitudes in the summer hemisphere. And the impact of the variations in temperature on errors is not significant.      

The Nonlinear Model of the Response of Airglow to Gravity Waves

In this paper, we develope a time-dependent, nonlinear, photochemical-dynamical 2-D model which is composed of 3 models: dynamical gravity wave model, middle atmospheric photochemical model, and airglow layer photochemical model. We use the model to study the effect of the gravity wave propagation on the airglow layer. The comparison between the effects of the different wavelength gravity wave on the airglow emission distributions is made. When the vertical wavelength of the gravity wave is close to or is shorter than the thickness of the airglow layer, the gravity wave can make complex structure of the airglow layer, such as the double and multi-peak structures of the airglow layers. However, the gravity wave that has long vertical wavelength can make large scale perturbation of the airglow emission distribution.     

SATI image processing and mesopause temperature determination

The Spectral Airglow Temperature Imager (SATI) instrument registers airglow coming from an annular mesopause segment. The temperatures of various points of this segment are retrieved by sectors of the registered images containing spectral information. A stage of SATI spectrogram processing connected with deriving spectral information from images and the determination of the rotational temperature of oxygen molecules emitting at the altitude of the mesopause is considered.     

Boundary of nighttime ozone chemical equilibrium in the mesopause region: Improved criterion of determining the boundary from satellite data

A modified derivation of the criterion of nighttime ozone chemical equilibrium (NOCE) in the mesopause region is presented. According to 3D model calculations, the improved criterion reproduces the lower boundary of the equilibrium much better than its earlier version. Processing of the SABER/TIMED data of 2021 has shown that the modified criterion elevates the NOCE boundary by ～ 0.1–1.7 km, depending on latitude and season. The proposed method of determining the condition of chemical equilibrium can be used to analyse the equilibrium of many trace gases in the stratosphere and troposphere important for different practical applications.