CEDAR Postdoc: Momentum Fluxes and Height Variability of Mesospheric Gravity Waves Obtained by Airglow Imagers

Utah State University, Logan UT

Investigators

Abstract

In the mesosphere/lower thermosphere region (~80-100 km), short-period gravity waves have a very important role influencing the global-scale dynamics. However, quantitative investigations on the effects of these gravity waves on the mesospheric region still need to be done. To understand their effects it is important to be able to quantify the momentum flux carried by these waves. Airglow imager data have proven to be very useful instruments for measuring small-scale horizontal structure of mesospheric gravity waves as well as their induced intensity perturbations. However, it is the temperature perturbations caused by the gravity waves that are needed to directly estimate the momentum flux carried by the gravity waves. Previously, researchers have applied a cancellation factor CF to relate the temperature to the intensity perturbations. However, the CF used is a model prediction and has not been verified sufficiently from the measurements because, until recently, it has been difficult to measure both intensity and temperature perturbations. For this program, investigators will use a special all-sky camera called the Mesospheric Temperature Mapper (MTM) to simultaneously measure the intensity and temperature waves to investigate CF and its dependence on vertical wavelength. The MTM data will then be used to make a seasonal study of momentum flux and to extend the capability to other types of all-sky cameras. This will allow a future, global scale, study to be made using the many imagers that are now operated around the world to measure gravity wave properties. In addition to this main study it is planned to help develop a tomographic imaging capability by extending the Rocky Mountain Imager Chain to permit new measurements of gravity wave structure height variability and to study the effects of wave breaking. The development of tomographic capabilities to study the gravity waves in the mesosphere, where they deposit their momentum, will significantly enhance our ability to investigate the dominant process involved. This study may open the door to quantitative investigations of momentum flux on a much larger scale using existing multi-station airglow and meteor radar measurements. Moreover, it will help us understand the seasonal variations and latitudinal dependences of energy transportation of gravity waves, leading to a clearer understanding of mesospheric climate and potential climate change.