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Communication Dans Un Congrès Année : 2008

Stereoscopic imaging of gravity waves in the mesosphere at low latitudes

Résumé

A program of stereo-imaging of the mesospheric near-infrared emissive layer has recently been initiated using two CCD cameras operating in a vis-`-vis observation mode at a separation a distance of 645 km. The images are analyzed in using a stereo-correlation method suitable for low contrast objects without discrete contours. This approach consists in calculating a normalized cross-correlation parameter for the intensities of matched points. The computer code calculates the altitude of the centroid of the emissive layer for each observed point and produces surface maps of the layer for 50x50 km2 areas. A first campaign of simultaneous observations at low latitude was conducted in July 2006 in the Peruvian Andes. The sites were: Cerro Cosmos (12° 09' 08.2" S, 75° 33' 49,3" W, altitude 4630m) and Cerro Tellolo (16° 33' 17.6"S, 71° 39' 59.4"W, altitude 2330m). The calculated surface maps are compared with pseudo-relief representations of the emission intensity. Both types of maps show significant wavy perturbations of the OH emission layer due to gravity waves. Two sets of image pairs will be presented. The retrieved mean altitudes of the emissive layer are respectively 87.1 and 89.5 km. The vertical amplitude of the waves are found to be 2.6 and 2 km. The horizontal wavelengths are 21.1 km and 24.6 km, The time periods are 18 and 34 minutes. The calculated oscillation kinetic energy density in the wave field at the emissive layer altitude is 3.9x10-4 watt/kg. This figure is comparable to the values obtained by partial reflection radiowave observations.
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Dates et versions

hal-00370910 , version 1 (25-03-2009)

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G. Moreels, M. Faivre, J. Clairemidi, M.N. Kouahla, J. W. Meriwether, et al.. Stereoscopic imaging of gravity waves in the mesosphere at low latitudes. 37th COSPAR Scientific Assembly, Jul 2008, Montréal (Québec), Canada. pp.124. ⟨hal-00370910⟩
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