Comparison of Gravity Wave activity Observed By Airglow Imaging From Two Different Latitudes in Brazil

An all-sky CCD imager for the OH, O2and OI View the MathML source airglow emissions was operated at Cachoeira Paulista (CP), Brazil (23°S,45°W), in collaboration with Utah State University, USA, during the period of 1998–2000. Another all-sky imager, which belongs to the Instituto Nacional de Pesquisas Espaciais, has been operating at São João do Cariri (Cariri), Brazil (7°S,36°W) since October 2000. Dominant gravity wave components were investigated by using the image data from the two sites. Wave characteristics observed at CP (October 1998–September 1999) show horizontal wavelengths of 5–View the MathML source, periods of 5–View the MathML source and horizontal phase velocities of 1–View the MathML source. Band-type waves (horizontal wavelengths between 10 and View the MathML source) showed a clear seasonal dependency in the horizontal propagation direction, propagating to the southeast in summer and to the northwest in winter. The Cariri data (September 2000–August 2001) showed horizontal wavelengths of 5–View the MathML source, with periods of 5–View the MathML source and horizontal phase velocities of 5–View the MathML source, much higher than CP. Band-type waves also exhibited a seasonal dependency in the horizontal propagation direction, propagating to southeast in summer and northeast in winter. The results are interpreted in terms of wind filtering and a non-uniform distribution of the gravity wave sources