Source tracing of thunderstorm generated inertia-gravity waves observed during the RADAGAST campaign in Niamey, Niger

Gravity waves generated by thunderstorms

“…The findings concerning the gravity waves generated by the thunderstorms have numerous implications on climate and weather studies. The perturbations caused by thunderstorms can change regional and large-scale circulations and affect global climate [48], [50], [52], [77]. Gravity waves carrying large amounts of momentum and energy are known to have a significant impact in the middle atmosphere by changing ozone and other gaseous concentrations and also impacting ionosphere electron distributions [8].…”

“…In order to understand and model these interactions, it is important to understand and quantify the role of Recent studies have described the middle atmospheric gravity waves dynamics on many fronts. Various observational studies using in-situ, ground-based and space-based data have helped greatly to realise the gravity wave scales, amplitudes, fluxes and spectra [10], [35], [51], [52], [43]- [50]. Numerous other studies have also highlighted the vertical propagation and the geographical variability.…”

“…Wavelet transform is used very commonly in the atmospheric studies in order to identify the spectrum of waves present in any signal using the time-frequency analysis [46], [48], [50], [77]. By decomposing a time series into time-frequency space, one is able to determine both the dominant modes of variability and how those modes vary in time.…”

“…Complex Morlet wavelet is a complex nonorthogonal wavelet which has been shown to work very well for the band of inertia-gravity waves [48], [50], [79]; and since this study is also focused on the inertia-gravity waves, complex Morlet wavelet is used for the wavelet transform. It is common to analyse the time-frequency spectrum of the horizontal kinetic energy density of the perturbation in order to identify the significant waves [48], [50], [77]. The wavelet analysis is performed on the averaged time series signals of u' 2 and v' 2 (between 19 and 25 km) and summed the wavelet transforms of them to obtain the time-frequency spectrum of the horizontal kinetic energy density.…”

“…It is important to calculate the horizontal components of for the ray tracing calculations; which is obtained by calculating the direction of phase propagation using equation (33) [46], [48], [50], [52].…”