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Effect of cyclone Nilofar on mesospheric wave dynamics as inferred from optical nightglow observations from Mount Abu, India
Author(s) -
Singh Ravindra P.,
Pallamraju Duggirala
Publication year - 2016
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja022412
Subject(s) - airglow , atmospheric sciences , outgoing longwave radiation , gravity wave , wavelength , convection , mesosphere , geology , climatology , meteorology , environmental science , physics , stratosphere , astrophysics , gravitational wave , optics
Mesospheric nightglow intensities at three emissions (O 2 (0–1), OH(6–2) bands, and Na(589.3 nm)) from a low‐latitude location, Gurushikhar, Mount Abu (24.6°N, 72.8°E), in India, showed similar wave features on 26 October 2014 with a common periodicity of around 4 h. A convective activity due to the cyclone Nilofar, which had developed in the Arabian Sea during 25–31 October 2014, was found to be the source as this too showed a gravity wave period coherent with that of the mesospheric emissions on the 26th. The periodicities at the source region were obtained using outgoing longwave radiation fluxes (derived from Kalpana‐1 satellite) which were used as a tracer of tropospheric activity. Cyclone Nilofar had two centers located at a distance of 1103 and 1665 km from the observational station. From the phase offset in time between residuals of O 2 and OH emission intensities and the observed common periodicity the vertical phase speed and wavelength have been found to be 1.13 ms −1 and 16.47 km. From the wavelet analyses it is seen that the travel time of the wave from the convection region to O 2 emission height was around 8.1 h. From these observations the horizontal phase speed and wavelength of the wave in the mesosphere were calculated to be 37.8 ms −1 and 553 km. These results thus provide not only unambiguous evidence on the vertical coupling of atmospheres engendered by the tropical cyclone Nilofar but also the characteristics of waves that exist during such cyclonic events.