Annales Geophysicae
www.ann-geophys.net
0992-7689
1432-0576
25
12
2007
10.5194/angeo-25-2479-2007
http://www.ann-geophys.net/25/2479/2007/
http://www.ann-geophys.net/25/2479/2007/angeo-25-2479-2007.html
http://www.ann-geophys.net/25/2479/2007/angeo-25-2479-2007.pdf
2479
2485
2008-01-02
Latitudinal and seasonal variability of gravity-wave energy in the South-West Indian Ocean
F. Chane-Ming
fchane@univ-reunion.fr
D. Faduilhe
J. Leveau
Laboratoire de l'Atmosphère et des Cyclones, Université de la Réunion, Météo-France, CNRS, UMR 8105, La Réunion, France
Vertical temperature profiles obtained by radiosonde and Raman lidar
measurements are used to investigate a climatology of total energy density
of gravity waves (GW) in the Upper Troposphere (UT) and the Lower
Stratosphere (LS) from 1992 to 2004 above Mahé (4° S, 55° E),
Tromelin (15° S, 54° E) and La Réunion (21° S, 55° E)
located in the tropical South-West Indian Ocean. The commonly used spectral
index value (<i>p</i>≈5/3) of the intrinsic frequency spectrum is used for
calculating estimated total energy density in the UT and LS. Estimated total
energy density provides good estimation of total energy density in the LS
but underestimates total energy density by one half in the UT above Mahé
and Tromelin probably due to the activity of near-inertial frequency waves.
Estimated total energy density reveals a strong seasonal variability as a
function of latitude and convection as an evident active source of GW
activity in the LS in austral summer. Above La Réunion, a semi-annual GW
activity is observed in the LS with the signature of the subtropical barrier
in the UT. Moreover, radiosondes and Raman lidar provide consistent GW
surveys in the UT/LS at heights<23 km above La Réunion.
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