The long-term climatology of high-frequency quasi-monochromatic gravity waves is presented using multi-year airglow images observed at Andes Lidar Observatory (ALO, 30.3ºS, 70.7ºW) in northern Chile. A large number of high-frequency gravity waves were retrieved from OH airglow images. The distribution of primary wave parameters including horizontal wavelength, vertical wavelength, intrinsic wave speed, and intrinsic wave period are obtained and are in the ranges of 20–30 km, 15–25 km, 50–100 ms-1, and 5–10 min, respectively. The waves tend to propagate against the local background winds and show clear seasonal variations. In austral winter (Ma–Aug), the observed wave occurrence frequency is higher and preferential wave propagation is equator-ward. In austral summer (Nov–Feb), the wave occurrence frequency is lower and the waves mostly propagate pole-ward. Critical-layer filtering plays an important role in determining the preferential propagation direction in certain months, especially for waves with a small observed phase speed (less than typical background winds). The wave occurrence and preferential propagation direction are shown to be related to the locations of convection activities nearby and their relative distance to ALO. However, other possible wave sources such as secondary wave generation and possible ducted propagation cannot be ruled out. The estimated momentum fluxes have typical values of a few to 10 m2s-2 and show seasonal variations with a clear anti-correlation with local background wind directions.
ESS Open Archive
Grant or Award Name
NSF grants AGS-1110199, AGS-1759471
Scholarly Commons Citation
Bing Cao, Alan Z Liu. Climatology of High-frequency Gravity Waves Observed by an Airglow Imager at Andes Lidar Observatory. ESS Open Archive. January 07, 2022. DOI: https://doi.org/10.1002/essoar.10510046.1