Durga Kafle

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AGU Joint Assembly

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Approximately 900 nights of observations with a Rayleigh-scatter lidar at Utah State University’s Atmospheric Lidar Observatory (41.7°N, 111.8°W, 1.47 km above sea level), spanning the 11-year period from late 1993 through 2004, have been reduced to derive nighttime temperature and relative density profiles between 45 and 90 km. Of these, 150 profiles that extend to 90 km or above were used in this work, which is based mainly on relative density data with 3-km altitude resolution and 1-hour temporal resolution. This is, we believe, the first comprehensive study of monochromatic gravity waves using Rayleigh-Scatter lidar observations extending through the entire mesosphere at mid-latitudes. The variations of relative density perturbations were used to identify the presence of monochromatic gravity waves. These waves have a clear downward phase progression (i.e., upward energy propagation) with the most prevalent vertical phase velocity (c ) of 0.6 ms-1 (2.2 km/hr). The most dominant vertical wavelengths (λ ) are between 12 and 16 km. The z z values of Brunt-Väisälä frequency, N (rad/sec), the maximum gravity wave frequency, were calculated by using seasonally averaged nightly temperature and temperature derivative profiles. Using the gravity wave dispersion relation and the values of c , λ , and N, other gravity wave parameters such as wave period (T ), horizontal z z p wavelength (λx), horizontal phase velocity (cx), and horizontal distance to the source region (X) were calculated. There appears to be a seasonal dependence in cz, Tp, λx, and X but not in λz and cx. Values of cz maximized in summer whereas Tp, λx, and X maximized in winter.


Presented at the AUG Joint Assembly. Poster available for download through link above.

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