Propagation of atmospheric gravity waves (AGWs) during super cyclone storm (Amphan) over Kolkata using GPS radiosonde and ERA-5 reanalysis data

The generation of atmospheric gravity waves (GWs) during super cyclone Amphan over Kolkata is investigated using radiosonde observations and ERA5 reanalysis data. The results show that the troposphere is dominated by vertical wavelengths of GWs (∼3.5-5 km), whereas shorter wavelengths (∼1.6-3.5 km) are observed in the lower stratosphere. The power spectral density analysis shows good consistency with the vertical wavelengths obtained from harmonic fitting of the radiosonde perturbation profiles. The combined analysis of wind and temperature perturbations, along with hodograph structures, indicates efficient upward propagation of gravity wave energy in the lower stratosphere. The total energy reaches peak values of ∼15- 20 J k g − 1 , with a pronounced enhancement over the Kolkata region during landfall, associated with low OLR flux. These findings suggest that intense convection associated with the cyclone acts as a primary source for gravity wave generation and vertical energy transport.