This project is an investigation of the dynamical transport by dissipating gravity waves and their impact on the vertical constituent structure in the mesopause region, using lidar observations and chemical models. To quantify the effects of dynamical transport, the University of Leeds chemical models of mesospheric Na and other minor constituents will be modified to include the vertical dynamical transport estimated from Na wind/temperature lidar measurements. The simulations of these modified models will then be compared with the extensive sodium lidar measurements that were conducted throughout the year at the Starfire Optical Range in New Mexico (SOR, Na, temperature, and flux observations) and Maui Space Surveillance System, in Hawaii (MSSS, Na, temperature, and flux observations). This work will be done in collaboration with Professor John M. C. Plane and his group at the University of Leeds. The objectives are to obtain quantitative estimates of vertical dynamical fluxes of various constituents, and compare their effects on the vertical distribution and chemistry of these constituents. The key scientific goals of this research are: 1) to verify the theoretical relationship between the vertical heat and constituent fluxes by analyzing the seasonal variations of the measured heat and Na fluxes at SOR and MSSS; 2) to upgrade the University of Leeds chemical models of mesospheric constituents to include the significant affects of GW transport by employing the relationships between heat and constituent fluxes; 3) to quantify the relative influence of GW flux on the seasonal variations of the structure of the mesospheric Na layer by comparing model predictions with observations; 4) to estimate the seasonal variations of the eddy diffusion coefficient profile between 80 and 105 km by tuning the Na model to reproduce the lidar observations at SOR and MSSS; 5) to assess the influence of GW transport on the structure of other important mesospheric constituents such as odd O and odd H. The project includes the participation of a post-doctoral researcher and a graduate student, who will gain experience in research on middle atmospheric dynamics and chemistry, engineering techniques in remote sensing, and signal processing.
The Earth's upper atmosphere (80 to 100 km above the ground) is constantly perturbed by many waves, which are generated mostly in the lower atmosphere. These waves have strong influence on the global atmospheric circulation and energy balance. The upper atmosphere is a transition region between the outer space and the atmosphere, and physical processes in this region largely determines how the Earth interactes with the sun. One significant effect of these waves is their ability of transporting mass vertically. This effect is difficult to measure because the vertical wind associated with the wave perturbations are very small. In this project, high resolution and accurate data obtained from LIDAR (LIght Detection and Ranging) measurements were used to estimate this transport effect. Seasonal variations of these processes have been characteried. Theoretical analysis was also performed to understand the relationships among several different transport processes, including the transport by waves, by the turbulence, and by wave-perturbed chemical reactions. We found that these transports are quite significant. These effects are currently not counted properly in most computer models of the atmosphere because of poor understanding of these transport processes. Incoporating these into models will lead to improvements of simulations of the global circulation and better estimates of the global mass transports.
