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Aura Science

Equatorial wave structure

Equatorial waves are waves that are trapped in the tropics and which can propagate only longitudinally and vertically. They are believed to play an important role in many climatological phenomena, such as the transport of water vapor and other trace constituents near the tropopause, the occurrence of clouds in the tropics, and control a substantial fraction of tropical rainfall variability.

HIRDLS temperature measurement sampling and resolution afford unprecedented views of the latitude-height structure of equatorial waves at altitudes above cloud tops in the tropical upper troposphere and stratosphere. Mixed Rossby-gravity waves with vertical wavelength as short as 4 km can be clearly seen in the data. Kelvin waves comprise a dominant signal throughout the 3 years of HIRDLS measurements. Time, height, and longitude variations are observed in these Kelvin waves.

Mixed Rossby-Gravity waves

(anti-symmetric about equator)

Equatorial-Rossby waves

Kelvin waves


Credit : Alexander, M. J., and D. A. Ortland (2010), Equatorial waves in High Resolution Dynamics Limb Sounder (HIRDLS) data, J. Geophys. Res., 115, D24111, doi:10.1029/2010JD014782.