CEDAR: Effects of Orographic Forcing on the Southern Mid-Latitude Mesosphere

Trustees Of Boston University, Boston

Investigators

Abstract

The investigation will determine the characteristics of orographic forcing and its contribution to the total occurrence of mesospheric gravity waves. The project entails the estimation of the momentum and energy flux associated with the mountain waves as well as the level of flux divergence, i.e., wave deposition, into the mesopause region. The project goals will be achieved using all-sky imaging observations of the mesosphere-lower thermosphere (MLT) mountain waves in conjunction with measurements from several types of multi-diagnostic instrumentation co-located at the El Leoncito Observatory in Argentina providing hydroxyl and oxygen winds, temperatures, and brightness. Additional satellite measurements of MLT temperature and airglow emission rate, as well as tropospheric/stratospheric winds and temperatures, will also be utilized in order to obtain a comprehensive characterization of the origin and behavior of the waves. The primary thrust of the project is to analyze gravity wave data generated by westerly winds flowing across the Andes and imaged in the immediate downwind region by their effects on the hydroxyl, oxygen, and sodium airglow emissions. Mountain wave events will be identified using tropospheric and stratospheric temperature measurements obtained from satellite radiances. These measurements, combined with mean wind information in the troposphere and stratosphere, will characterize the forcing conditions for mountain wave generation. Other satellite measurements will provide mean state temperature covering a large vertical extent of the atmosphere which will help tie the lower atmosphere measurements to the MLT region measurements. The subject of orographic forcing of atmospheric gravity waves is of current interest as part of efforts to determine the importance of coupling of various kinds of tropospheric processes to the upper atmosphere. The work will advance these efforts.