The proposed three-year project is to study the mesosphere/thermosphere/ionosphere (MTI) dynamics separating tides, gravity and planetary waves and their influence on the composition; the zonal characterization of the gravity wave field and acoustic gravity wave activity and their coupling with tidal motion, planetary waves and horizontal wind changes; possible climatological trends in mesopause temperature with a separation of long term trends from local variability and solar influence. The project employs ground-based observations of a series of airglow optical emissions, temperature and ionospheric critical frequencies f0F2 obtained at four longitudinally remote ground stations within a narrow midlatitude band centered at ~40N. The project team encompasses 27 research scientists, engineers, technical personnel and graduate students, with expertise in optical remote sensing of the atmosphere, middle atmospheric dynamics, aeronomy and instrument design from Bulgaria, Republic of Georgia, Kazakhstan and Spain. During the course of the project the following tasks are expected to be accomplished. 1. The optical instruments will be calibrated for the purpose of studying dynamical perturbation of airglow intensities, including internal gravity waves and their statistical characteristics at Northern midlatitudes. 2. A comprehensive set of data will be obtained of the inter-seasonal variability of the O(1S), OH and O2 airglow, f0F2 frequencies and rotational temperatures in the MTI to study planetary scale perturbations. Analysis will be conducted on the available time-series to identify long-term trends in the observed variability. 3. Model simulations will be performed to study the coupling of the low thermosphere with the ionosphere employing optical observations of the O(1D) emission at 630 nm wavelength and ionosonde parameters (i.e. f0F2 frequencies). 4. The development of non-linear theory of spontaneous generation of acoustic gravity waves in the middle atmosphere and interpretation of self-ordering wave structures in the MLT region employing optical observations in the visible and infrared spectral region. 5. Ground-based airglow and temperature observations will be combined with correlative and retrospective satellite observations to provide measurements of the global dynamical state of the atmosphere from 60 to 250 km. 6. The results obtained will be compared with respective observations within the CAWSES framework, whenever possible. It is proposed that three Science Workshops be held in Spain, Kazakhstan and Bulgaria to present and discuss results from the conducted observations and analyses, and access the progress on the project's research programme. All observations will be stored in a standardized database, which will be made available for use by the international scientific community. At the end of the project the results from the 11 project tasks will be presented for publication in international scientific journals.