Articles | Volume 9, issue 1
Research article
18 Jan 2016
Research article |  | 18 Jan 2016

Mesospheric gravity wave characteristics and identification of their sources around spring equinox over Indian low latitudes

M. Sivakandan, I. Paulino, A. Taori, and K. Niranjan

Abstract. We report OI557.7 nm night airglow observations with the help of a charged-couple device (CCD)-based all-sky camera from a low-latitude station, Gadanki (13.5° N; 79.2° E). Based on the data collected during March and April over 3 years, from 2012 to 2014 (except March 2013), we characterize the small-scale gravity wave properties. During this period, 50 gravity wave events were detected. The horizontal wavelengths of the gravity waves are found to ranging from 12 to 42 km with the phase velocity 20–90 m s−1. In most cases, these waves were propagating northward with only a few occurrences of southward propagation. In the present novel investigation from the Indian sector, each of the wave events was reverse-ray-traced to its source. The outgoing longwave radiation (OLR) suggested that tropospheric convection was a possible source for generation of the observed waves. It was found that approximately 66 % of the events were triggered directly by the convection.

Short summary
The small-scale gravity waves are the least understood processes in the middle-atmospheric variability. Using airglow imaging, we provide new measurements of gravity wave propagation over equatorial latitudes in India. We find that propagation of waves is often in the opposite direction to the tropospheric convective regions. These waves are found to have horizontal wavelengths ranging from 12 to 42 km, with the phase velocities in the 20 to 90 km range.