Thesis (Ph.D.) - Cairo University - Faculty of Science - Department of Astronomy, Meteorology

In this study, we review the characteristics of the seasonal cycle of gravity waves between 2012 to 2020 at different latitudes using temperatures measured by lidar and satellite. We study the energy densities of gravity waves in three different latitudes: Andenes in Norway (69 N), K{u00A8}uhlungsborn in Germany ( 54 N), and Cairo in Egypt ( 30 N). For the first two locations, the data measured by both the lidar and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite are used in addition to ERA-5 reanalysis data. To separate the temperature perturbations caused by gravity waves, a filter on vertical wavelength ( z < 15 km) and another filter on wave period ( < 8 h) were applied. From these temperature fluctuations, the Gravity Wave Potential Energy Density (GWPED) is calculated. The comparison between the lidar and the satellite temperature analysis showed that both regions show an apparent seasonal variability of GWPED with a maximum in winter and a minimum in summer. However, the amplitude of winter to summer variability differs from lidar to satellite. GWPED from reanalysis is smaller compared to lidar, and the difference increases with altitude in winter. All measured and reanalysis data confirmed the larger GWPED of K{u00A8}uhlungsborn over Andenes, but the exact reason for this is not yet evident

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